Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755191Ab1BHRUu (ORCPT ); Tue, 8 Feb 2011 12:20:50 -0500 Received: from ovro.ovro.caltech.edu ([192.100.16.2]:45968 "EHLO ovro.ovro.caltech.edu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754512Ab1BHRUs (ORCPT ); Tue, 8 Feb 2011 12:20:48 -0500 Date: Tue, 8 Feb 2011 09:20:46 -0800 From: "Ira W. Snyder" To: Dmitry Torokhov Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/2] misc: add CARMA DATA-FPGA Access Driver Message-ID: <20110208172046.GB10125@ovro.caltech.edu> References: <1297121021-3522-1-git-send-email-iws@ovro.caltech.edu> <1297121021-3522-2-git-send-email-iws@ovro.caltech.edu> <20110208073309.GB906@core.coreip.homeip.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110208073309.GB906@core.coreip.homeip.net> User-Agent: Mutt/1.5.20 (2009-06-14) X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.2.6 (ovro.ovro.caltech.edu); Tue, 08 Feb 2011 09:20:47 -0800 (PST) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 52973 Lines: 1735 On Mon, Feb 07, 2011 at 11:33:10PM -0800, Dmitry Torokhov wrote: > Hi Ira, > > On Mon, Feb 07, 2011 at 03:23:40PM -0800, Ira W. Snyder wrote: > > This driver allows userspace to access the data processing FPGAs on the > > OVRO CARMA board. It has two modes of operation: > > > > 1) random access > > > > This allows users to poke any DATA-FPGA registers by using mmap to map > > the address region directly into their memory map. > > > > 2) correlation dumping > > > > When correlating, the DATA-FPGA's have special requirements for getting > > the data out of their memory before the next correlation. This nominally > > happens at 64Hz (every 15.625ms). If the data is not dumped before the > > next correlation, data is lost. > > > > The data dumping driver handles buffering up to 1 second worth of > > correlation data from the FPGAs. This lowers the realtime scheduling > > requirements for the userspace process reading the device. > > Kind of a fly-by review but it looks like the locking in the driver > needs work. > Hi Dmitry, Thanks for the review. I have a few comments inline below. > > > > Signed-off-by: Ira W. Snyder > > --- > > drivers/misc/Kconfig | 1 + > > drivers/misc/Makefile | 1 + > > drivers/misc/carma/Kconfig | 9 + > > drivers/misc/carma/Makefile | 1 + > > drivers/misc/carma/carma-fpga.c | 1446 +++++++++++++++++++++++++++++++++++++++ > > 5 files changed, 1458 insertions(+), 0 deletions(-) > > create mode 100644 drivers/misc/carma/Kconfig > > create mode 100644 drivers/misc/carma/Makefile > > create mode 100644 drivers/misc/carma/carma-fpga.c > > > > diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig > > index 4d073f1..f457f14 100644 > > --- a/drivers/misc/Kconfig > > +++ b/drivers/misc/Kconfig > > @@ -457,5 +457,6 @@ source "drivers/misc/eeprom/Kconfig" > > source "drivers/misc/cb710/Kconfig" > > source "drivers/misc/iwmc3200top/Kconfig" > > source "drivers/misc/ti-st/Kconfig" > > +source "drivers/misc/carma/Kconfig" > > > > endif # MISC_DEVICES > > diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile > > index 98009cc..2c1610e 100644 > > --- a/drivers/misc/Makefile > > +++ b/drivers/misc/Makefile > > @@ -42,3 +42,4 @@ obj-$(CONFIG_ARM_CHARLCD) += arm-charlcd.o > > obj-$(CONFIG_PCH_PHUB) += pch_phub.o > > obj-y += ti-st/ > > obj-$(CONFIG_AB8500_PWM) += ab8500-pwm.o > > +obj-y += carma/ > > diff --git a/drivers/misc/carma/Kconfig b/drivers/misc/carma/Kconfig > > new file mode 100644 > > index 0000000..4be183f > > --- /dev/null > > +++ b/drivers/misc/carma/Kconfig > > @@ -0,0 +1,9 @@ > > +config CARMA_FPGA > > + tristate "CARMA DATA-FPGA Access Driver" > > + depends on FSL_SOC && PPC_83xx && MEDIA_SUPPORT && HAS_DMA && FSL_DMA > > + select VIDEOBUF_DMA_SG > > + default n > > + help > > + Say Y here to include support for communicating with the data > > + processing FPGAs on the OVRO CARMA board. > > + > > diff --git a/drivers/misc/carma/Makefile b/drivers/misc/carma/Makefile > > new file mode 100644 > > index 0000000..0b69fa7 > > --- /dev/null > > +++ b/drivers/misc/carma/Makefile > > @@ -0,0 +1 @@ > > +obj-$(CONFIG_CARMA_FPGA) += carma-fpga.o > > diff --git a/drivers/misc/carma/carma-fpga.c b/drivers/misc/carma/carma-fpga.c > > new file mode 100644 > > index 0000000..52620b3 > > --- /dev/null > > +++ b/drivers/misc/carma/carma-fpga.c > > @@ -0,0 +1,1446 @@ > > +/* > > + * CARMA DATA-FPGA Access Driver > > + * > > + * Copyright (c) 2009-2010 Ira W. Snyder > > + * > > + * This program is free software; you can redistribute it and/or modify it > > + * under the terms of the GNU General Public License as published by the > > + * Free Software Foundation; either version 2 of the License, or (at your > > + * option) any later version. > > + */ > > + > > +/* > > + * FPGA Memory Dump Format > > + * > > + * FPGA #0 control registers (32 x 32-bit words) > > + * FPGA #1 control registers (32 x 32-bit words) > > + * FPGA #2 control registers (32 x 32-bit words) > > + * FPGA #3 control registers (32 x 32-bit words) > > + * SYSFPGA control registers (32 x 32-bit words) > > + * FPGA #0 correlation array (NUM_CORL0 correlation blocks) > > + * FPGA #1 correlation array (NUM_CORL1 correlation blocks) > > + * FPGA #2 correlation array (NUM_CORL2 correlation blocks) > > + * FPGA #3 correlation array (NUM_CORL3 correlation blocks) > > + * > > + * Each correlation array consists of: > > + * > > + * Correlation Data (2 x NUM_LAGSn x 32-bit words) > > + * Pipeline Metadata (2 x NUM_METAn x 32-bit words) > > + * Quantization Counters (2 x NUM_QCNTn x 32-bit words) > > + * > > + * The NUM_CORLn, NUM_LAGSn, NUM_METAn, and NUM_QCNTn values come from > > + * the FPGA configuration registers. They do not change once the FPGA's > > + * have been programmed, they only change on re-programming. > > + */ > > + > > +/* > > + * Basic Description: > > + * > > + * This driver is used to capture correlation spectra off of the four data > > + * processing FPGAs. The FPGAs are often reprogrammed at runtime, therefore > > + * this driver supports dynamic enable/disable of capture while the device > > + * remains open. > > + * > > + * The nominal capture rate is 64Hz (every 15.625ms). To facilitate this fast > > + * capture rate, all buffers are pre-allocated to avoid any potentially long > > + * running memory allocations while capturing. > > + * > > + * There are three lists which are used to keep track of the different states > > + * of data buffers. > > + * > > + * 1) free list > > + * This list holds all empty data buffers which are ready to receive data. > > + * > > + * 2) inflight list > > + * This list holds data buffers which are currently waiting for a DMA operation > > + * to complete. > > + * > > + * 3) used list > > + * This list holds data buffers which have been filled, and are waiting to be > > + * read by userspace. > > + * > > + * All buffers start life on the free list, then move successively to the > > + * inflight list, and then to the used list. After they have been read by > > + * userspace, they are moved back to the free list. The cycle repeats as long > > + * as necessary. > > + */ > > + > > +/* > > + * Notes on the IRQ masking scheme: > > + * > > + * The IRQ masking scheme here is different than most other hardware. The only > > + * way for the DATA-FPGAs to detect if the kernel has taken too long to copy > > + * the data is if the status registers are not cleared before the next > > + * correlation data dump is ready. > > + * > > + * The interrupt line is connected to the status registers, such that when they > > + * are cleared, the interrupt is de-asserted. Therein lies our problem. We need > > + * to schedule a long-running DMA operation and return from the interrupt > > + * handler quickly, but we cannot clear the status registers. > > + * > > + * To handle this, the system controller FPGA has the capability to connect the > > + * interrupt line to a user-controlled GPIO pin. This pin is driven high > > + * (unasserted) and left that way. To mask the interrupt, we change the > > + * interrupt source to the GPIO pin. Tada, we hid the interrupt. :) > > + */ > > + > > +#include > > +#include > > +#include > > +#include > > +#include > > +#include > > +#include > > +#include > > +#include > > +#include > > +#include > > +#include > > + > > +#include > > + > > +/* system controller registers */ > > +#define SYS_IRQ_SOURCE_CTL 0x24 > > +#define SYS_IRQ_OUTPUT_EN 0x28 > > +#define SYS_IRQ_OUTPUT_DATA 0x2C > > +#define SYS_IRQ_INPUT_DATA 0x30 > > + > > +/* GPIO IRQ line assignment */ > > +#define IRQ_CORL_DONE 0x10 > > + > > +/* FPGA registers */ > > +#define MMAP_REG_VERSION 0x00 > > +#define MMAP_REG_CORL_CONF1 0x08 > > +#define MMAP_REG_CORL_CONF2 0x0C > > +#define MMAP_REG_STATUS 0x48 > > + > > +#define SYS_FPGA_BLOCK 0xF0000000 > > + > > +static const char drv_name[] = "carma-fpga"; > > + > > +#define NUM_FPGA 4 > > + > > +#define MIN_DATA_BUFS 8 > > +#define MAX_DATA_BUFS 64 > > + > > +struct fpga_info { > > + unsigned int num_lag_ram; > > + unsigned int blk_size; > > +}; > > + > > +struct data_buf { > > + struct list_head entry; > > + struct videobuf_dmabuf vb; > > + bool mapped; > > + size_t size; > > +}; > > + > > +struct fpga_device { > > + struct miscdevice miscdev; > > + struct device *dev; > > + struct mutex mutex; > > + > > + /* FPGA registers and information */ > > + struct fpga_info info[NUM_FPGA]; > > + void __iomem *regs; > > + int irq; > > + > > + /* FPGA Physical Address/Size Information */ > > + resource_size_t phys_addr; > > + size_t phys_size; > > + > > + /* DMA structures */ > > + struct sg_table corl_table; > > + unsigned int corl_nents; > > + struct dma_chan *chan; > > + > > + /* Protection for all members below */ > > + spinlock_t lock; > > + > > + /* Device enable/disable flag */ > > + bool enabled; > > + > > + /* Correlation data buffers */ > > + wait_queue_head_t wait; > > + struct list_head free; > > + struct list_head used; > > + struct list_head inflight; > > + > > + /* Information about data buffers */ > > + unsigned int num_dropped; > > + unsigned int num_buffers; > > + size_t bufsize; > > +}; > > + > > +struct fpga_reader { > > + struct fpga_device *priv; > > + struct data_buf *buf; > > + off_t buf_start; > > +}; > > + > > +#define inode_to_dev(inode) container_of(inode->i_cdev, struct fpga_device, cdev) > > + > > +/* > > + * Data Buffer Allocation Helpers > > + */ > > + > > +static int data_map_buffer(struct device *dev, struct data_buf *buf) > > +{ > > + int ret; > > + > > + /* if the buffer is already mapped, we're done */ > > + if (buf->mapped) > > + return 0; > > + > > This is a local function, not library. Can't we keep track whether a > buffer is mapped or not? > Sure. I'll review the driver so I don't need this variable anymore. > > + ret = videobuf_dma_map(dev, &buf->vb); > > + if (ret) > > + return ret; > > + > > + buf->mapped = true; > > + return 0; > > +} > > + > > +static void data_unmap_buffer(struct device *dev, struct data_buf *buf) > > +{ > > + /* the buffer is already unmapped, we're done */ > > + if (!buf->mapped) > > + return; > > + > > + videobuf_dma_unmap(dev, &buf->vb); > > + buf->mapped = false; > > +} > > + > > +/** > > + * data_free_buffer() - free a single data buffer and all allocated memory > > + * @dev: the DMA device to map for > > + * @buf: the buffer to free > > + * > > + * This will free all of the pages allocated to the given data buffer, and > > + * then free the structure itself > > + */ > > +static void data_free_buffer(struct device *dev, struct data_buf *buf) > > +{ > > + /* It is ok to free a NULL buffer */ > > + if (!buf) > > + return; > > + > > + /* Make sure the buffer is not on any list */ > > + list_del_init(&buf->entry); > > And what happens if it is? Should it be WARN_ON(!list_empty()) instead? > This was only defensive programming. Everywhere this function is called, the buffer has already been removed from the list. > > + > > + /* unmap it for DMA */ > > + data_unmap_buffer(dev, buf); > > + > > + /* free all memory */ > > + videobuf_dma_free(&buf->vb); > > + kfree(buf); > > +} > > + > > +/** > > + * data_alloc_buffer() - allocate and fill a data buffer with pages > > + * @dev: the DMA device to map for > > + * @bytes: the number of bytes required > > + * > > + * This allocates all space needed for a data buffer, and gets it ready to be > > + * used in a DMA transaction. It only needs to be used, never mapped before > > + * use. This avoids calling vmalloc in hardirq context. > > + * > > + * Returns NULL on failure > > + */ > > +static struct data_buf *data_alloc_buffer(struct device *dev, const size_t bytes) > > +{ > > + unsigned int nr_pages; > > + struct data_buf *buf; > > + int ret; > > + > > + /* calculate the number of pages necessary */ > > + nr_pages = DIV_ROUND_UP(bytes, PAGE_SIZE); > > + > > + /* allocate the buffer structure */ > > + buf = kzalloc(sizeof(*buf), GFP_KERNEL); > > + if (!buf) > > + goto out_return; > > + > > + /* initialize internal fields */ > > + INIT_LIST_HEAD(&buf->entry); > > + buf->size = bytes; > > + > > + /* allocate the videobuf */ > > + videobuf_dma_init(&buf->vb); > > + ret = videobuf_dma_init_kernel(&buf->vb, DMA_FROM_DEVICE, nr_pages); > > + if (ret) > > + goto out_free_buf; > > + > > + /* map it for DMA */ > > + ret = data_map_buffer(dev, buf); > > + if (ret) > > + goto out_free_videobuf; > > + > > + return buf; > > + > > +out_free_videobuf: > > + videobuf_dma_free(&buf->vb); > > +out_free_buf: > > + kfree(buf); > > +out_return: > > + return NULL; > > +} > > + > > +/** > > + * data_free_buffers() - free all allocated buffers > > + * @priv: the driver's private data structure > > + * > > + * Free all buffers allocated by the driver (except those currently in the > > + * process of being read by userspace). > > + * > > + * LOCKING: must hold dev->mutex > > + * CONTEXT: user > > + */ > > +static void data_free_buffers(struct fpga_device *priv) > > +{ > > + struct data_buf *buf, *tmp; > > + > > + spin_lock_irq(&priv->lock); > > + BUG_ON(!list_empty(&priv->inflight)); > > + > > + list_for_each_entry_safe(buf, tmp, &priv->free, entry) { > > + list_del_init(&buf->entry); > > + spin_unlock_irq(&priv->lock); > > + data_free_buffer(priv->dev, buf); > > + spin_lock_irq(&priv->lock); > > + } > > This is messed up. If there is concurrent access to the free list then > it is not safe to continue iterating list after releasing the lock, you > need to do: > > spin_lock_irq(&priv->lock); > while (!list_empty(&priv->free)) { > buf = list_first_entry(&priv->free, struct data_buf, entry); > list_del_init(&buf->entry); > spin_unlock_irq(&priv->lock); > data_free_buffer(priv->dev, buf); > spin_lock_irq(&priv->lock); > } > > BUT, the function is only called when you disable (or fail to enable) device > which, at this point, should be quiesced, thus all this locking is not > really needed. > Correct. I thought it would be clearer to reviewers if I always used the lock to protect a data structure, even when it isn't technically needed. > > + > > + list_for_each_entry_safe(buf, tmp, &priv->used, entry) { > > + list_del_init(&buf->entry); > > + spin_unlock_irq(&priv->lock); > > + data_free_buffer(priv->dev, buf); > > + spin_lock_irq(&priv->lock); > > + } > > + > > + priv->num_buffers = 0; > > + priv->bufsize = 0; > > + > > + spin_unlock_irq(&priv->lock); > > +} > > + > > +/** > > + * data_alloc_buffers() - allocate 1 seconds worth of data buffers > > + * @priv: the driver's private data structure > > + * > > + * Allocate enough buffers for a whole second worth of data > > + * > > + * This routine will attempt to degrade nicely by succeeding even if a full > > + * second worth of data buffers could not be allocated, as long as a minimum > > + * number were allocated. In this case, it will print a message to the kernel > > + * log. > > + * > > + * CONTEXT: user > > + * LOCKING: must hold dev->mutex > > + * > > + * Returns 0 on success, -ERRNO otherwise > > + */ > > +static int data_alloc_buffers(struct fpga_device *priv) > > +{ > > + struct data_buf *buf; > > + int i; > > + > > + for (i = 0; i < MAX_DATA_BUFS; i++) { > > + buf = data_alloc_buffer(priv->dev, priv->bufsize); > > + if (!buf) > > + break; > > + > > + spin_lock_irq(&priv->lock); > > + list_add_tail(&buf->entry, &priv->free); > > + spin_unlock_irq(&priv->lock); > > Again, can someone be accessing this list aleady? > Nope. The list needs to be protected from concurrent access when the device is running, but not when it is stopped. Same as above. > > + } > > + > > + /* Make sure we allocated the minimum required number of buffers */ > > + if (i < MIN_DATA_BUFS) { > > + dev_err(priv->dev, "Unable to allocate enough data buffers\n"); > > + data_free_buffers(priv); > > + return -ENOMEM; > > + } > > + > > + /* Warn if we are running in a degraded state, but do not fail */ > > + if (i < MAX_DATA_BUFS) { > > + dev_warn(priv->dev, "Unable to allocate one second worth of " > > + "buffers, using %d buffers instead\n", i); > > + } > > + > > + priv->num_buffers = i; > > + return 0; > > +} > > + > > +/* > > + * DMA Operations Helpers > > + */ > > + > > +/** > > + * fpga_start_addr() - get the physical address a DATA-FPGA > > + * @priv: the driver's private data structure > > + * @fpga: the DATA-FPGA number (zero based) > > + */ > > +static dma_addr_t fpga_start_addr(struct fpga_device *priv, unsigned int fpga) > > +{ > > + return priv->phys_addr + 0x400000 + (0x80000 * fpga); > > +} > > + > > +/** > > + * fpga_block_addr() - get the physical address of a correlation data block > > + * @priv: the driver's private data structure > > + * @fpga: the DATA-FPGA number (zero based) > > + * @blknum: the correlation block number (zero based) > > + */ > > +static dma_addr_t fpga_block_addr(struct fpga_device *priv, unsigned int fpga, > > + unsigned int blknum) > > +{ > > + return fpga_start_addr(priv, fpga) + (0x10000 * (1 + blknum)); > > +} > > + > > +#define REG_BLOCK_SIZE (32 * 4) > > + > > +/** > > + * data_setup_corl_table() - create the scatterlist for correlation dumps > > + * @priv: the driver's private data structure > > + * > > + * Create the scatterlist for transferring a correlation dump from the > > + * DATA FPGAs. This structure will be reused for each buffer than needs > > + * to be filled with correlation data. > > + * > > + * Returns 0 on success, -ERRNO otherwise > > + */ > > +static int data_setup_corl_table(struct fpga_device *priv) > > +{ > > + struct sg_table *table = &priv->corl_table; > > + struct scatterlist *sg; > > + struct fpga_info *info; > > + int i, j, ret; > > + > > + /* Calculate the number of entries needed */ > > + priv->corl_nents = (1 + NUM_FPGA) * REG_BLOCK_SIZE; > > + for (i = 0; i < NUM_FPGA; i++) > > + priv->corl_nents += priv->info[i].num_lag_ram; > > + > > + /* Allocate the scatterlist table */ > > + ret = sg_alloc_table(table, priv->corl_nents, GFP_KERNEL); > > + if (ret) { > > + dev_err(priv->dev, "unable to allocate DMA table\n"); > > + return ret; > > + } > > + > > + /* Add the DATA FPGA registers to the scatterlist */ > > + sg = table->sgl; > > + for (i = 0; i < NUM_FPGA; i++) { > > + sg_dma_address(sg) = fpga_start_addr(priv, i); > > + sg_dma_len(sg) = REG_BLOCK_SIZE; > > + sg = sg_next(sg); > > + } > > + > > + /* Add the SYS-FPGA registers to the scatterlist */ > > + sg_dma_address(sg) = SYS_FPGA_BLOCK; > > + sg_dma_len(sg) = REG_BLOCK_SIZE; > > + sg = sg_next(sg); > > + > > + /* Add the FPGA correlation data blocks to the scatterlist */ > > + for (i = 0; i < NUM_FPGA; i++) { > > + info = &priv->info[i]; > > + for (j = 0; j < info->num_lag_ram; j++) { > > + sg_dma_address(sg) = fpga_block_addr(priv, i, j); > > + sg_dma_len(sg) = info->blk_size; > > + sg = sg_next(sg); > > + } > > + } > > + > > + /* > > + * All physical addresses and lengths are present in the structure > > + * now. It can be reused for every FPGA DATA interrupt > > + */ > > + return 0; > > +} > > + > > +/* > > + * FPGA Register Access Helpers > > + */ > > + > > +static void fpga_write_reg(struct fpga_device *priv, unsigned int fpga, > > + unsigned int reg, u32 val) > > +{ > > + iowrite32be(val, priv->regs + 0x400000 + (fpga * 0x80000) + reg); > > +} > > + > > +static u32 fpga_read_reg(struct fpga_device *priv, unsigned int fpga, > > + unsigned int reg) > > +{ > > + return ioread32be(priv->regs + 0x400000 + (fpga * 0x80000) + reg); > > +} > > + > > +/** > > + * data_calculate_bufsize() - calculate the data buffer size required > > + * @priv: the driver's private data structure > > + * > > + * Calculate the total buffer size needed to hold a single block > > + * of correlation data > > + * > > + * CONTEXT: user > > + * > > + * Returns 0 on success, -ERRNO otherwise > > + */ > > +static int data_calculate_bufsize(struct fpga_device *priv) > > +{ > > + u32 num_corl, num_lags, num_meta, num_qcnt, num_pack; > > + u32 conf1, conf2, version; > > + u32 num_lag_ram, blk_size; > > + int i; > > + > > + /* Each buffer starts with the 5 FPGA register areas */ > > + priv->bufsize = (1 + NUM_FPGA) * REG_BLOCK_SIZE; > > + > > + /* Read and store the configuration data for each FPGA */ > > + for (i = 0; i < NUM_FPGA; i++) { > > + version = fpga_read_reg(priv, i, MMAP_REG_VERSION); > > + conf1 = fpga_read_reg(priv, i, MMAP_REG_CORL_CONF1); > > + conf2 = fpga_read_reg(priv, i, MMAP_REG_CORL_CONF2); > > + > > + /* minor version 2 and later */ > > + if ((version & 0x000000FF) >= 2) { > > + num_corl = (conf1 & 0x000000F0) >> 4; > > + num_pack = (conf1 & 0x00000F00) >> 8; > > + num_lags = (conf1 & 0x00FFF000) >> 12; > > + num_meta = (conf1 & 0x7F000000) >> 24; > > + num_qcnt = (conf2 & 0x00000FFF) >> 0; > > + } else { > > + num_corl = (conf1 & 0x000000F0) >> 4; > > + num_pack = 1; /* implied */ > > + num_lags = (conf1 & 0x000FFF00) >> 8; > > + num_meta = (conf1 & 0x7FF00000) >> 20; > > + num_qcnt = (conf2 & 0x00000FFF) >> 0; > > + } > > + > > + num_lag_ram = (num_corl + num_pack - 1) / num_pack; > > + blk_size = ((num_pack * num_lags) + num_meta + num_qcnt) * 8; > > + > > + priv->info[i].num_lag_ram = num_lag_ram; > > + priv->info[i].blk_size = blk_size; > > + priv->bufsize += num_lag_ram * blk_size; > > + > > + dev_dbg(priv->dev, "FPGA %d NUM_CORL: %d\n", i, num_corl); > > + dev_dbg(priv->dev, "FPGA %d NUM_PACK: %d\n", i, num_pack); > > + dev_dbg(priv->dev, "FPGA %d NUM_LAGS: %d\n", i, num_lags); > > + dev_dbg(priv->dev, "FPGA %d NUM_META: %d\n", i, num_meta); > > + dev_dbg(priv->dev, "FPGA %d NUM_QCNT: %d\n", i, num_qcnt); > > + dev_dbg(priv->dev, "FPGA %d BLK_SIZE: %d\n", i, blk_size); > > + } > > + > > + dev_dbg(priv->dev, "TOTAL BUFFER SIZE: %zu bytes\n", priv->bufsize); > > + return 0; > > +} > > + > > +/* > > + * Interrupt Handling > > + */ > > + > > +/** > > + * data_disable_interrupts() - stop the device from generating interrupts > > + * @priv: the driver's private data structure > > + * > > + * Hide interrupts by switching to GPIO interrupt source > > + * > > + * LOCKING: must hold dev->lock > > + */ > > +static void data_disable_interrupts(struct fpga_device *priv) > > +{ > > + /* hide the interrupt by switching the IRQ driver to GPIO */ > > + iowrite32be(0x2F, priv->regs + SYS_IRQ_SOURCE_CTL); > > +} > > + > > +/** > > + * data_enable_interrupts() - allow the device to generate interrupts > > + * @priv: the driver's private data structure > > + * > > + * Unhide interrupts by switching to the FPGA interrupt source. At the > > + * same time, clear the DATA-FPGA status registers. > > + * > > + * LOCKING: must hold dev->lock > > + */ > > +static void data_enable_interrupts(struct fpga_device *priv) > > +{ > > + /* clear the actual FPGA corl_done interrupt */ > > + fpga_write_reg(priv, 0, MMAP_REG_STATUS, 0x0); > > + fpga_write_reg(priv, 1, MMAP_REG_STATUS, 0x0); > > + fpga_write_reg(priv, 2, MMAP_REG_STATUS, 0x0); > > + fpga_write_reg(priv, 3, MMAP_REG_STATUS, 0x0); > > + > > + /* flush the writes */ > > + fpga_read_reg(priv, 0, MMAP_REG_STATUS); > > + > > + /* switch back to the external interrupt source */ > > + iowrite32be(0x3F, priv->regs + SYS_IRQ_SOURCE_CTL); > > +} > > + > > +/** > > + * data_dma_cb() - DMAEngine callback for DMA completion > > + * @data: the driver's private data structure > > + * > > + * Complete a DMA transfer from the DATA-FPGA's > > + * > > + * This is called via the DMA callback mechanism, and will handle moving the > > + * completed DMA transaction to the used list, and then wake any processes > > + * waiting for new data > > + * > > + * CONTEXT: any, softirq expected > > + */ > > +static void data_dma_cb(void *data) > > +{ > > + struct fpga_device *priv = data; > > + struct data_buf *buf; > > + unsigned long flags; > > + > > + spin_lock_irqsave(&priv->lock, flags); > > + > > + /* clear the FPGA status and re-enable interrupts */ > > + data_enable_interrupts(priv); > > + > > + /* If the inflight list is empty, we've got a bug */ > > + BUG_ON(list_empty(&priv->inflight)); > > + > > + /* Grab the first buffer from the inflight list */ > > + buf = list_first_entry(&priv->inflight, struct data_buf, entry); > > + list_del_init(&buf->entry); > > + > > + /* Add it to the used list */ > > + list_add_tail(&buf->entry, &priv->used); > > + > > + spin_unlock_irqrestore(&priv->lock, flags); > > + > > + /* We've changed both the inflight and used lists, so we need > > + * to wake up any processes that are blocking for those events */ > > + wake_up(&priv->wait); > > +} > > + > > +/** > > + * data_submit_dma() - prepare and submit the required DMA to fill a buffer > > + * @priv: the driver's private data structure > > + * @buf: the data buffer > > + * > > + * Prepare and submit the necessary DMA transactions to fill a correlation > > + * data buffer. > > + * > > + * LOCKING: must hold dev->lock > > + * CONTEXT: hardirq only > > + * > > + * Returns 0 on success, -ERRNO otherwise > > + */ > > +static int data_submit_dma(struct fpga_device *priv, struct data_buf *buf) > > +{ > > + struct scatterlist *dst_sg, *src_sg; > > + unsigned int dst_nents, src_nents; > > + struct dma_chan *chan = priv->chan; > > + struct dma_async_tx_descriptor *tx; > > + dma_cookie_t cookie; > > + dma_addr_t dst, src; > > + > > + dst_sg = buf->vb.sglist; > > + dst_nents = buf->vb.sglen; > > + > > + src_sg = priv->corl_table.sgl; > > + src_nents = priv->corl_nents; > > + > > + /* > > + * All buffers passed to this function should be ready and mapped > > + * for DMA already. Therefore, we don't need to do anything except > > + * submit it to the Freescale DMA Engine for processing > > + */ > > + > > + /* setup the scatterlist to scatterlist transfer */ > > + tx = chan->device->device_prep_dma_sg(chan, > > + dst_sg, dst_nents, > > + src_sg, src_nents, > > + 0); > > + if (!tx) { > > + dev_err(priv->dev, "unable to prep scatterlist DMA\n"); > > + return -ENOMEM; > > + } > > + > > + /* submit the transaction to the DMA controller */ > > + cookie = tx->tx_submit(tx); > > + if (dma_submit_error(cookie)) { > > + dev_err(priv->dev, "unable to submit scatterlist DMA\n"); > > + return -ENOMEM; > > + } > > + > > + /* Prepare the re-read of the SYS-FPGA block */ > > + dst = sg_dma_address(dst_sg) + (NUM_FPGA * REG_BLOCK_SIZE); > > + src = SYS_FPGA_BLOCK; > > + tx = chan->device->device_prep_dma_memcpy(chan, dst, src, > > + REG_BLOCK_SIZE, > > + DMA_PREP_INTERRUPT); > > + if (!tx) { > > + dev_err(priv->dev, "unable to prep SYS-FPGA DMA\n"); > > + return -ENOMEM; > > + } > > + > > + /* Setup the callback */ > > + tx->callback = data_dma_cb; > > + tx->callback_param = priv; > > + > > + /* submit the transaction to the DMA controller */ > > + cookie = tx->tx_submit(tx); > > + if (dma_submit_error(cookie)) { > > + dev_err(priv->dev, "unable to submit SYS-FPGA DMA\n"); > > + return -ENOMEM; > > + } > > + > > + return 0; > > +} > > + > > +#define CORL_DONE 0x1 > > +#define CORL_ERR 0x2 > > + > > +static irqreturn_t data_irq(int irq, void *dev_id) > > +{ > > + struct fpga_device *priv = dev_id; > > + struct data_buf *buf; > > + u32 status; > > + int i; > > + > > + /* detect spurious interrupts via FPGA status */ > > + for (i = 0; i < 4; i++) { > > + status = fpga_read_reg(priv, i, MMAP_REG_STATUS); > > + if (!(status & (CORL_DONE | CORL_ERR))) { > > + dev_err(priv->dev, "spurious irq detected (FPGA)\n"); > > + return IRQ_NONE; > > + } > > + } > > + > > + /* detect spurious interrupts via raw IRQ pin readback */ > > + status = ioread32be(priv->regs + SYS_IRQ_INPUT_DATA); > > + if (status & IRQ_CORL_DONE) { > > + dev_err(priv->dev, "spurious irq detected (IRQ)\n"); > > + return IRQ_NONE; > > + } > > + > > + spin_lock(&priv->lock); > > + > > + /* hide the interrupt by switching the IRQ driver to GPIO */ > > + data_disable_interrupts(priv); > > + > > + /* Check that we actually have a free buffer */ > > + if (list_empty(&priv->free)) { > > + priv->num_dropped++; > > + data_enable_interrupts(priv); > > + goto out_unlock; > > + } > > + > > + buf = list_first_entry(&priv->free, struct data_buf, entry); > > + list_del_init(&buf->entry); > > + > > + /* Check the buffer size */ > > + BUG_ON(buf->size != priv->bufsize); > > + > > + /* Submit a DMA transfer to get the correlation data */ > > + if (data_submit_dma(priv, buf)) { > > + dev_err(priv->dev, "Unable to setup DMA transfer\n"); > > + list_add_tail(&buf->entry, &priv->free); > > + data_enable_interrupts(priv); > > + goto out_unlock; > > + } > > + > > + /* DMA setup succeeded, GO!!! */ > > + list_add_tail(&buf->entry, &priv->inflight); > > + dma_async_memcpy_issue_pending(priv->chan); > > + > > +out_unlock: > > + spin_unlock(&priv->lock); > > + return IRQ_HANDLED; > > +} > > + > > +/* > > + * Realtime Device Enable Helpers > > + */ > > + > > +/** > > + * data_device_enable() - enable the device for buffered dumping > > + * @priv: the driver's private data structure > > + * > > + * Enable the device for buffered dumping. Allocates buffers and hooks up > > + * the interrupt handler. When this finishes, data will come pouring in. > > + * > > + * LOCKING: must hold dev->mutex > > + * CONTEXT: user context only > > + * > > + * Returns 0 on success, -ERRNO otherwise > > + */ > > +static int data_device_enable(struct fpga_device *priv) > > +{ > > + u32 val; > > + int ret; > > + > > + /* multiple enables are safe: they do nothing */ > > + if (priv->enabled) > > + return 0; > > + > > + /* check that the FPGAs are programmed */ > > + val = ioread32be(priv->regs + 0x44); > > + if (!(val & (1 << 18))) { > > + dev_err(priv->dev, "DATA-FPGAs are not enabled\n"); > > + return -ENODATA; > > + } > > + > > + /* read the FPGAs to calculate the buffer size */ > > + ret = data_calculate_bufsize(priv); > > + if (ret) { > > + dev_err(priv->dev, "unable to calculate buffer size\n"); > > + goto out_error; > > + } > > + > > + /* allocate the correlation data buffers */ > > + ret = data_alloc_buffers(priv); > > + if (ret) { > > + dev_err(priv->dev, "unable to allocate buffers\n"); > > + goto out_error; > > + } > > + > > + /* setup the source scatterlist for dumping correlation data */ > > + ret = data_setup_corl_table(priv); > > + if (ret) { > > + dev_err(priv->dev, "unable to setup correlation DMA table\n"); > > + goto out_error; > > + } > > + > > + /* switch to the external FPGA IRQ line */ > > + data_enable_interrupts(priv); > > + > > + /* hookup the irq handler */ > > + ret = request_irq(priv->irq, data_irq, IRQF_SHARED, drv_name, priv); > > + if (ret) { > > + dev_err(priv->dev, "unable to request IRQ handler\n"); > > + goto out_error; > > + } > > + > > + /* success, we're enabled */ > > + priv->enabled = true; > > + return 0; > > + > > +out_error: > > + sg_free_table(&priv->corl_table); > > + priv->corl_nents = 0; > > + > > + data_free_buffers(priv); > > + return ret; > > +} > > + > > +/** > > + * data_device_disable() - disable the device for buffered dumping > > + * @priv: the driver's private data structure > > + * > > + * Disable the device for buffered dumping. Stops new DMA transactions from > > + * being generated, waits for all outstanding DMA to complete, and then frees > > + * all buffers. > > + * > > + * LOCKING: must hold dev->mutex > > + * CONTEXT: user only > > + * > > + * Returns 0 on success, -ERRNO otherwise > > + */ > > +static int data_device_disable(struct fpga_device *priv) > > +{ > > + struct list_head *list; > > + int ret; > > + > > + /* allow multiple disable */ > > + if (!priv->enabled) > > + return 0; > > + > > + /* switch to the internal GPIO IRQ line */ > > + data_disable_interrupts(priv); > > + > > + /* unhook the irq handler */ > > + free_irq(priv->irq, priv); > > + > > + /* wait for all outstanding DMA to complete */ > > + list = &priv->inflight; > > + > > + spin_lock_irq(&priv->lock); > > + while (!list_empty(list)) { > > + spin_unlock_irq(&priv->lock); > > + > > + ret = wait_event_interruptible(priv->wait, list_empty(list)); > > + if (ret) > > + return -ERESTARTSYS; > > + > > + spin_lock_irq(&priv->lock); > > + } > > + spin_unlock_irq(&priv->lock); > > Locking is not needed - if you disable interrupyts what would put more > stuff on the list? > The locking is definitely needed. You've missed a critical piece of information. There are *two* devices we are interacting with here, and BOTH generate interrupts. 1) DATA-FPGA (generates interrupts for dumping) 2) Freescale DMA Engine (generates interrupts at DMA completion) The data_disable_interrupts() routine disables DATA-FPGA interrupts. This loop waits until the DMA engine has completed. The driver goes like this: - several buffers on the free list - DATA-FPGA interrupt occurs data_irq() - disable DATA-FPGA interrupts - take a buffer from the free list - setup DMA data_submit_dma() - put buffer on the inflight list back in data_irq() - start DMA in data_irq() - DMA finishes, DMA interrupt occurs data_dma_cb() - re-enable DATA-FPGA interrupts - take first buffer off the inflight list - put buffer on the used list > > + > > + /* free the correlation table */ > > + sg_free_table(&priv->corl_table); > > + priv->corl_nents = 0; > > + > > + /* free all of the buffers */ > > + data_free_buffers(priv); > > + priv->enabled = false; > > + return 0; > > +} > > + > > +/* > > + * SYSFS Attributes > > + */ > > + > > +/* > > + * Count the number of entries in the given list > > + */ > > +static unsigned int list_num_entries(struct list_head *list) > > +{ > > + struct list_head *entry; > > + unsigned int ret = 0; > > + > > + list_for_each(entry, list) > > + ret++; > > + > > + return ret; > > +} > > + > > +static ssize_t data_num_buffers_show(struct device *dev, > > + struct device_attribute *attr, char *buf) > > +{ > > + struct fpga_device *priv = dev_get_drvdata(dev); > > + unsigned int num; > > + > > + spin_lock_irq(&priv->lock); > > + num = priv->num_buffers; > > + spin_unlock_irq(&priv->lock); > > This spin lock is pointless, priv->num_buffers might be already changed > here, you can't guarantee that you show accurate data. > Correct, I know this. I just wanted to protect the data structure at all points of use in the driver. Would an atomic_t be better for this, or should I just remove the locking completely? Personally, it seems very confusing to me when a data structure is protected by a lock in some places, and not in others. > > + > > + return snprintf(buf, PAGE_SIZE, "%u\n", num); > > +} > > + > > +static ssize_t data_bufsize_show(struct device *dev, > > + struct device_attribute *attr, char *buf) > > +{ > > + struct fpga_device *priv = dev_get_drvdata(dev); > > + size_t num; > > + > > + spin_lock_irq(&priv->lock); > > + num = priv->bufsize; > > + spin_unlock_irq(&priv->lock); > > Same here. > > > + > > + return snprintf(buf, PAGE_SIZE, "%zu\n", num); > > +} > > + > > +static ssize_t data_inflight_show(struct device *dev, > > + struct device_attribute *attr, char *buf) > > +{ > > + struct fpga_device *priv = dev_get_drvdata(dev); > > + unsigned int num; > > + > > + spin_lock_irq(&priv->lock); > > + num = list_num_entries(&priv->inflight); > > + spin_unlock_irq(&priv->lock); > > And here. > > > + > > + return snprintf(buf, PAGE_SIZE, "%u\n", num); > > +} > > + > > +static ssize_t data_free_show(struct device *dev, > > + struct device_attribute *attr, char *buf) > > +{ > > + struct fpga_device *priv = dev_get_drvdata(dev); > > + unsigned int num; > > + > > + spin_lock_irq(&priv->lock); > > + num = list_num_entries(&priv->free); > > + spin_unlock_irq(&priv->lock); > > + > > And here. > > > + return snprintf(buf, PAGE_SIZE, "%u\n", num); > > +} > > + > > +static ssize_t data_used_show(struct device *dev, > > + struct device_attribute *attr, char *buf) > > +{ > > + struct fpga_device *priv = dev_get_drvdata(dev); > > + unsigned int num; > > + > > + spin_lock_irq(&priv->lock); > > + num = list_num_entries(&priv->used); > > + spin_unlock_irq(&priv->lock); > > + > > Ditto. > > > + return snprintf(buf, PAGE_SIZE, "%u\n", num); > > +} > > + > > +static ssize_t data_num_dropped_show(struct device *dev, > > + struct device_attribute *attr, char *buf) > > +{ > > + struct fpga_device *priv = dev_get_drvdata(dev); > > + unsigned int num; > > + > > + spin_lock_irq(&priv->lock); > > + num = priv->num_dropped; > > + spin_unlock_irq(&priv->lock); > > + > > Yep.. > > > + return snprintf(buf, PAGE_SIZE, "%u\n", num); > > +} > > + > > +static ssize_t data_en_show(struct device *dev, struct device_attribute *attr, > > + char *buf) > > +{ > > + struct fpga_device *priv = dev_get_drvdata(dev); > > + ssize_t count; > > + > > + if (mutex_lock_interruptible(&priv->mutex)) > > + return -ERESTARTSYS; > > + > > + count = snprintf(buf, PAGE_SIZE, "%u\n", priv->enabled); > > + mutex_unlock(&priv->mutex); > > By the time buf gets all the way to userspace, yep you guessed it... > > > + return count; > > +} > > + > > +static ssize_t data_en_set(struct device *dev, struct device_attribute *attr, > > + const char *buf, size_t count) > > +{ > > + struct fpga_device *priv = dev_get_drvdata(dev); > > + unsigned long enable; > > + int ret; > > + > > + ret = strict_strtoul(buf, 0, &enable); > > + if (ret) { > > + dev_err(priv->dev, "unable to parse enable input\n"); > > + return -EINVAL; > > + } > > + > > + if (mutex_lock_interruptible(&priv->mutex)) > > + return -ERESTARTSYS; > > Why don't > > error = mutex_lock_interruptible(&priv->mutex); > if (error) > return error; > > - do not clobber perfectly valid error codes. > That's what the Linux Device Drivers 3rd Edition book does. See page 112. I will change it to fix the return code. > > + > > + if (enable) > > + ret = data_device_enable(priv); > > + else > > + ret = data_device_disable(priv); > > + > > + if (ret) { > > + dev_err(priv->dev, "device %s failed\n", > > + enable ? "enable" : "disable"); > > + count = ret; > > + goto out_unlock; > > + } > > + > > +out_unlock: > > + mutex_unlock(&priv->mutex); > > + return count; > > +} > > + > > +static DEVICE_ATTR(num_buffers, S_IRUGO, data_num_buffers_show, NULL); > > +static DEVICE_ATTR(buffer_size, S_IRUGO, data_bufsize_show, NULL); > > +static DEVICE_ATTR(num_inflight, S_IRUGO, data_inflight_show, NULL); > > +static DEVICE_ATTR(num_free, S_IRUGO, data_free_show, NULL); > > +static DEVICE_ATTR(num_used, S_IRUGO, data_used_show, NULL); > > +static DEVICE_ATTR(num_dropped, S_IRUGO, data_num_dropped_show, NULL); > > +static DEVICE_ATTR(enable, S_IWUGO | S_IRUGO, data_en_show, data_en_set); > > + > > +static struct attribute *data_sysfs_attrs[] = { > > + &dev_attr_num_buffers.attr, > > + &dev_attr_buffer_size.attr, > > + &dev_attr_num_inflight.attr, > > + &dev_attr_num_free.attr, > > + &dev_attr_num_used.attr, > > + &dev_attr_num_dropped.attr, > > + &dev_attr_enable.attr, > > + NULL, > > +}; > > Are all of these really needed or most of them are for debug? > Most are for debugging. They have proved useful a few times in production to track down bugs. > > + > > +static const struct attribute_group rt_sysfs_attr_group = { > > + .attrs = data_sysfs_attrs, > > +}; > > + > > +/* > > + * FPGA Realtime Data Character Device > > + */ > > + > > +static int data_open(struct inode *inode, struct file *filp) > > +{ > > + /* > > + * The miscdevice layer puts our struct miscdevice into the > > + * filp->private_data field. We use this to find our private > > + * data and then overwrite it with our own private structure. > > + */ > > + struct fpga_device *priv = container_of(filp->private_data, > > + struct fpga_device, miscdev); > > + struct fpga_reader *reader; > > + int ret; > > + > > + /* allocate private data */ > > + reader = kzalloc(sizeof(*reader), GFP_KERNEL); > > + if (!reader) > > + return -ENOMEM; > > + > > + reader->priv = priv; > > + reader->buf = NULL; > > + > > + filp->private_data = reader; > > + ret = nonseekable_open(inode, filp); > > + if (ret) { > > + dev_err(priv->dev, "nonseekable-open failed\n"); > > + kfree(reader); > > + return ret; > > + } > > + > > + return 0; > > +} > > + > > +static int data_release(struct inode *inode, struct file *filp) > > +{ > > + struct fpga_reader *reader = filp->private_data; > > + struct fpga_device *priv = reader->priv; > > + > > + /* free the per-reader structure */ > > + data_free_buffer(priv->dev, reader->buf); > > + kfree(reader); > > + filp->private_data = NULL; > > + return 0; > > +} > > + > > +static ssize_t data_read(struct file *filp, char __user *ubuf, size_t count, > > + loff_t *f_pos) > > +{ > > + struct fpga_reader *reader = filp->private_data; > > + struct fpga_device *priv = reader->priv; > > + struct list_head *used = &priv->used; > > + struct data_buf *dbuf; > > + size_t avail; > > + void *data; > > + int ret; > > + > > + /* check if we already have a partial buffer */ > > + if (reader->buf) { > > + dbuf = reader->buf; > > + goto have_buffer; > > + } > > + > > + spin_lock_irq(&priv->lock); > > + > > + /* Block until there is at least one buffer on the used list */ > > + while (list_empty(used)) { > > + spin_unlock_irq(&priv->lock); > > + > > + if (filp->f_flags & O_NONBLOCK) > > + return -EAGAIN; > > + > > + if (wait_event_interruptible(priv->wait, !list_empty(used))) > > + return -ERESTARTSYS; > > + > > And somebody grabs that entry here... > > > + spin_lock_irq(&priv->lock); > > + } > > + > > + /* Grab the first buffer off of the used list */ > > + dbuf = list_first_entry(used, struct data_buf, entry); > > And list is empty so you grabgarbage. > > > + list_del_init(&dbuf->entry); > > + > > + spin_unlock_irq(&priv->lock); > > Shoudl be: > > struct data_buf *dbuf = NULL; > ... > > if (list_empty(&priv->used) && (filp->f_flags & O_NONBLOCK)) > return -EAGAIN; > > error = wait_event_interruptible(priv->wait, !list_empty(&priv->used); > if (error) > return error; > > spin_lock_irq(&priv->lock); > if (!list_empty(&priv->used)) { > buf = list_first_entry(&priv->used, struct data_buf, entry); > list_del_init(&dbuf->entry); > } > spin_unlock_irq(&priv->lock); > > if (dbuf) { > .. deal with the buffer > } > I'm pretty sure you're wrong. Go back and re-think my loop. This is a common idiom straight of out LDD3 pages 153-154. You should note that it is only possible to exit the loop with the lock held AND !list_empty(used). The lock protects the used list, and therefore, there must be a buffer on the list. > > + > > + /* Buffers are always mapped: unmap it */ > > + data_unmap_buffer(priv->dev, dbuf); > > + > > + /* save the buffer for later */ > > + reader->buf = dbuf; > > + reader->buf_start = 0; > > + > > + /* we removed a buffer from the used list: wake any waiters */ > > + wake_up(&priv->wait); > > + > > +have_buffer: > > + /* Get the number of bytes available */ > > + avail = dbuf->size - reader->buf_start; > > + data = dbuf->vb.vaddr + reader->buf_start; > > + > > + /* Get the number of bytes we can transfer */ > > + count = min(count, avail); > > + > > + /* Copy the data to the userspace buffer */ > > + if (copy_to_user(ubuf, data, count)) > > + return -EFAULT; > > + > > + /* Update the amount of available space */ > > + avail -= count; > > + > > + /* Lock against concurrent enable/disable */ > > + if (mutex_lock_interruptible(&priv->mutex)) > > + return -ERESTARTSYS; > > + > > + /* Still some space available: save the buffer for later */ > > + if (avail != 0) { > > + reader->buf_start += count; > > + reader->buf = dbuf; > > + goto out_unlock; > > + } > > + > > + /* > > + * No space is available in this buffer > > + * > > + * This is a complicated decision: > > + * - if the device is not enabled: free the buffer > > + * - if the buffer is too small: free the buffer > > + */ > > + if (!priv->enabled || dbuf->size != priv->bufsize) { > > + data_free_buffer(priv->dev, dbuf); > > + reader->buf = NULL; > > + goto out_unlock; > > + } > > + > > + /* > > + * The buffer is safe to recycle: remap it and finish > > + * > > + * If this fails, we pretend that the read never happened, and return > > + * -EFAULT to userspace. They'll retry the read again. > > + */ > > + ret = data_map_buffer(priv->dev, dbuf); > > + if (ret) { > > + dev_err(priv->dev, "unable to remap buffer for DMA\n"); > > + count = -EFAULT; > > + goto out_unlock; > > + } > > + > > + /* Add the buffer back to the free list */ > > + reader->buf = NULL; > > + spin_lock_irq(&priv->lock); > > + list_add_tail(&dbuf->entry, &priv->free); > > + spin_unlock_irq(&priv->lock); > > + > > +out_unlock: > > + mutex_unlock(&priv->mutex); > > + return count; > > +} > > + > > +static unsigned int data_poll(struct file *filp, struct poll_table_struct *tbl) > > +{ > > + struct fpga_reader *reader = filp->private_data; > > + struct fpga_device *priv = reader->priv; > > + unsigned int mask = 0; > > + > > + poll_wait(filp, &priv->wait, tbl); > > + > > + spin_lock_irq(&priv->lock); > > + > > + if (!list_empty(&priv->used)) > > + mask |= POLLIN | POLLRDNORM; > > + > > + spin_unlock_irq(&priv->lock); > > No lock is needed. > Why not? For example, there are two readers: 1) blocked in poll() 2) blocked in poll() A single buffer gets added to the used list. I should only unblock one of them with (POLLIN | POLLRDNORM), correct? Otherwise one of them must have a spurious wakeup. I think that's incorrect (or undesirable) behavior. Again, it seems very inconsistent and confusing to me to protect the used list with a spinlock in some places and not in others. > > + return mask; > > +} > > + > > +static int data_mmap(struct file *filp, struct vm_area_struct *vma) > > +{ > > + struct fpga_reader *reader = filp->private_data; > > + struct fpga_device *priv = reader->priv; > > + unsigned long offset, vsize, psize, addr; > > + > > + /* VMA properties */ > > + offset = vma->vm_pgoff << PAGE_SHIFT; > > + vsize = vma->vm_end - vma->vm_start; > > + psize = priv->phys_size - offset; > > + addr = (priv->phys_addr + offset) >> PAGE_SHIFT; > > + > > + /* Check against the FPGA region's physical memory size */ > > + if (vsize > psize) { > > + dev_err(priv->dev, "requested mmap mapping too large\n"); > > + return -EINVAL; > > + } > > + > > + /* IO memory (stop cacheing) */ > > + vma->vm_flags |= VM_IO | VM_RESERVED; > > + vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot); > > + > > + return io_remap_pfn_range(vma, vma->vm_start, addr, vsize, > > + vma->vm_page_prot); > > +} > > + > > +static const struct file_operations data_fops = { > > + .owner = THIS_MODULE, > > + .open = data_open, > > + .release = data_release, > > + .read = data_read, > > + .poll = data_poll, > > + .mmap = data_mmap, > > + .llseek = no_llseek, > > +}; > > + > > +/* > > + * OpenFirmware Device Subsystem > > + */ > > + > > +static bool dma_filter(struct dma_chan *chan, void *data) > > +{ > > + /* > > + * DMA Channel #0 is used for the FPGA Programmer, so ignore it > > + * > > + * This probably won't survive an unload/load cycle of the Freescale > > + * DMAEngine driver, but that won't be a problem > > + */ > > + if (chan->chan_id == 0 && chan->device->dev_id == 0) > > + return false; > > + > > + return true; > > +} > > + > > +static int data_of_probe(struct platform_device *op, > > + const struct of_device_id *match) > > +{ > > + struct device_node *of_node = op->dev.of_node; > > + struct device *this_device; > > + struct fpga_device *priv; > > + struct resource res; > > + dma_cap_mask_t mask; > > + int ret; > > + > > + /* Allocate private data */ > > + priv = kzalloc(sizeof(*priv), GFP_KERNEL); > > + if (!priv) { > > + dev_err(&op->dev, "Unable to allocate device private data\n"); > > + ret = -ENOMEM; > > + goto out_return; > > + } > > + > > + dev_set_drvdata(&op->dev, priv); > > + priv->dev = &op->dev; > > + > > + /* Setup the misc device */ > > + priv->miscdev.minor = MISC_DYNAMIC_MINOR; > > + priv->miscdev.name = drv_name; > > + priv->miscdev.fops = &data_fops; > > + > > + /* Get the physical address of the FPGA registers */ > > + ret = of_address_to_resource(of_node, 0, &res); > > + if (ret) { > > + dev_err(&op->dev, "Unable to find FPGA physical address\n"); > > + ret = -ENODEV; > > + goto out_free_priv; > > + } > > + > > + priv->phys_addr = res.start; > > + priv->phys_size = resource_size(&res); > > + > > + /* ioremap the registers for use */ > > + priv->regs = of_iomap(of_node, 0); > > + if (!priv->regs) { > > + dev_err(&op->dev, "Unable to ioremap registers\n"); > > + ret = -ENOMEM; > > + goto out_free_priv; > > + } > > + > > + dma_cap_zero(mask); > > + dma_cap_set(DMA_MEMCPY, mask); > > + dma_cap_set(DMA_INTERRUPT, mask); > > + dma_cap_set(DMA_SLAVE, mask); > > + dma_cap_set(DMA_SG, mask); > > + > > + /* Request a DMA channel */ > > + priv->chan = dma_request_channel(mask, dma_filter, NULL); > > + if (!priv->chan) { > > + dev_err(&op->dev, "Unable to request DMA channel\n"); > > + ret = -ENODEV; > > + goto out_unmap_regs; > > + } > > + > > + /* Find the correct IRQ number */ > > + priv->irq = irq_of_parse_and_map(of_node, 0); > > + if (priv->irq == NO_IRQ) { > > + dev_err(&op->dev, "Unable to find IRQ line\n"); > > + ret = -ENODEV; > > + goto out_release_dma; > > + } > > + > > + dev_set_drvdata(priv->dev, priv); > > + mutex_init(&priv->mutex); > > + spin_lock_init(&priv->lock); > > + INIT_LIST_HEAD(&priv->free); > > + INIT_LIST_HEAD(&priv->used); > > + INIT_LIST_HEAD(&priv->inflight); > > + init_waitqueue_head(&priv->wait); > > + > > + /* Drive the GPIO for FPGA IRQ high (no interrupt) */ > > + iowrite32be(IRQ_CORL_DONE, priv->regs + SYS_IRQ_OUTPUT_DATA); > > + > > + /* Register the miscdevice */ > > + ret = misc_register(&priv->miscdev); > > + if (ret) { > > + dev_err(&op->dev, "Unable to register miscdevice\n"); > > + goto out_irq_dispose_mapping; > > + } > > + > > + /* Create the sysfs files */ > > + this_device = priv->miscdev.this_device; > > + dev_set_drvdata(this_device, priv); > > + ret = sysfs_create_group(&this_device->kobj, &rt_sysfs_attr_group); > > + if (ret) { > > + dev_err(&op->dev, "Unable to create sysfs files\n"); > > + goto out_misc_deregister; > > + } > > + > > + dev_info(&op->dev, "CARMA FPGA Realtime Data Driver Loaded\n"); > > + return 0; > > + > > +out_misc_deregister: > > + misc_deregister(&priv->miscdev); > > +out_irq_dispose_mapping: > > + irq_dispose_mapping(priv->irq); > > +out_release_dma: > > + dma_release_channel(priv->chan); > > +out_unmap_regs: > > + iounmap(priv->regs); > > +out_free_priv: > > + mutex_destroy(&priv->mutex); > > + kfree(priv); > > +out_return: > > + return ret; > > +} > > + > > +static int data_of_remove(struct platform_device *op) > > +{ > > + struct fpga_device *priv = dev_get_drvdata(&op->dev); > > + struct device *this_device = priv->miscdev.this_device; > > + > > + /* make sure the IRQ line is disabled */ > > + mutex_lock(&priv->mutex); > > + data_device_disable(priv); > > + mutex_unlock(&priv->mutex); > > Remove attributes first and lose the mutex. > Ok. > > + > > + sysfs_remove_group(&this_device->kobj, &rt_sysfs_attr_group); > > + misc_deregister(&priv->miscdev); > > + irq_dispose_mapping(priv->irq); > > + dma_release_channel(priv->chan); > > + iounmap(priv->regs); > > + mutex_destroy(&priv->mutex); > > + kfree(priv); > > + > > + return 0; > > +} > > + > > +static struct of_device_id data_of_match[] = { > > + { .compatible = "carma,carma-fpga", }, > > + {}, > > +}; > > + > > +static struct of_platform_driver data_of_driver = { > > + .probe = data_of_probe, > > + .remove = data_of_remove, > > + .driver = { > > + .name = drv_name, > > + .of_match_table = data_of_match, > > + .owner = THIS_MODULE, > > + }, > > +}; > > + > > +/* > > + * Module Init / Exit > > + */ > > + > > +static int __init data_init(void) > > +{ > > + return of_register_platform_driver(&data_of_driver); > > +} > > + > > +static void __exit data_exit(void) > > +{ > > + of_unregister_platform_driver(&data_of_driver); > > +} > > + > > +MODULE_AUTHOR("Ira W. Snyder "); > > +MODULE_DESCRIPTION("CARMA DATA-FPGA Access Driver"); > > +MODULE_LICENSE("GPL"); > > + > > +module_init(data_init); > > +module_exit(data_exit); > > Thanks. > Thanks again for the review. I'd love to read your replies to some of my comments. :) Ira -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/