From: Appana Durga Kedareswara Rao <appana.durga.rao@xilinx.com>
To: Moritz Fischer <moritz.fischer@ettus.com>
CC: "vinod.koul@intel.com" <vinod.koul@intel.com>,
        "dan.j.williams@intel.com" <dan.j.williams@intel.com>,
        Michal Simek <michals@xilinx.com>,
        "Soren Brinkmann" <sorenb@xilinx.com>,
        "anirudha@xilinx.com" <anirudha@xilinx.com>,
        "dmaengine@vger.kernel.org" <dmaengine@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@lists.infradead.org>
Subject: RE: [RESEND PATCH] dmaengine: Add Xilinx AXI Direct Memory Access
 Engine driver support
Thread-Topic: [RESEND PATCH] dmaengine: Add Xilinx AXI Direct Memory Access
 Engine driver support
Thread-Index: AQHQ2QHg+Rvxg0g5LEC/HL9Es0tMcJ4TWkYAgAEI2aA=
Date: Thu, 20 Aug 2015 05:41:23 +0000
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Hi Moritz Fischer,

	Thanks for reviewing the patch.

> -----Original Message-----
> From: Moritz Fischer [mailto:moritz.fischer@ettus.com]
> Sent: Thursday, August 20, 2015 3:21 AM
> To: Appana Durga Kedareswara Rao
> Cc: vinod.koul@intel.com; dan.j.williams@intel.com; Michal Simek; Soren
> Brinkmann; Appana Durga Kedareswara Rao; anirudha@xilinx.com;
> dmaengine@vger.kernel.org; linux-kernel@vger.kernel.org; linux-arm-kernel;
> Srikanth Thokala
> Subject: Re: [RESEND PATCH] dmaengine: Add Xilinx AXI Direct Memory Access
> Engine driver support
> 
> Hi there,
> 
> see comment below. I just did a quick compile test. Will take another look once I
> synthesized an image.
> 
> On Mon, Aug 17, 2015 at 8:31 AM, Kedareswara rao Appana
> <appana.durga.rao@xilinx.com> wrote:
> > This is the driver for the AXI Direct Memory Access (AXI DMA) core,
> > which is a soft Xilinx IP core that provides high- bandwidth direct
> > memory access between memory and AXI4-Stream type target peripherals.
> >
> > Signed-off-by: Srikanth Thokala <sthokal@xilinx.com>
> > Signed-off-by: Kedareswara rao Appana <appanad@xilinx.com>
> > ---
> > The deivce tree doc got applied in the slave-dmaengine.git.
> >
> > Forgot to include dmaengine@vger.kernel.org in the cc list resending
> > the patch.
> >
> > Changes in v8:
> > - Updated the SG handling as suggested by Nicolae Rosia.
> > - Removed the unnecessary xilinx_dma_channel_set_config API the properties
> >   in this API is not being used by the driver.
> > Changes in v7:
> > - Updated license in the driver as suggested by Paul.
> > - Corrected return value in is_idle funtion.
> > Changes in v6:
> > - Fixed Odd indention in the Kconfig.
> > - used GFP_NOWAIT instead of GFP_KERNEL during the desc allocation
> > - Calculated residue in the tx_status instead of complete_descriptor.
> > - Update copy right to 2015.
> > - Modified spin_lock handling moved the spin_lock to the appropriate
> > functions (instead of xilinx_dma_start_transfer doing it
> xilinx_dma_issue_pending api).
> > - device_control and declare slave caps updated as per newer APi's.
> > Changes in v5:
> > - Modified the xilinx_dma.h header file location to the
> >   include/linux/dma/xilinx_dma.h
> > Changes in v4:
> > - Add direction field to DMA descriptor structure and removed from
> >   channel structure to avoid duplication.
> > - Check for DMA idle condition before changing the configuration.
> > - Residue is being calculated in complete_descriptor() and is reported
> >   to slave driver.
> > Changes in v3:
> > - Rebased on 3.16-rc7
> > Changes in v2:
> > - Simplified the logic to set SOP and APP words in prep_slave_sg().
> > - Corrected function description comments to match the return type.
> > - Fixed some minor comments as suggested by Andy.
> >
> >  drivers/dma/Kconfig             |   13 +
> >  drivers/dma/xilinx/Makefile     |    1 +
> >  drivers/dma/xilinx/xilinx_dma.c | 1179
> > +++++++++++++++++++++++++++++++++++++++
> >  3 files changed, 1193 insertions(+)
> >  create mode 100644 drivers/dma/xilinx/xilinx_dma.c
> >
> > diff --git a/drivers/dma/Kconfig b/drivers/dma/Kconfig index
> > 88d474b..5e95f07 100644
> > --- a/drivers/dma/Kconfig
> > +++ b/drivers/dma/Kconfig
> > @@ -507,4 +507,17 @@ config QCOM_BAM_DMA
> >           Enable support for the QCOM BAM DMA controller.  This controller
> >           provides DMA capabilities for a variety of on-chip devices.
> >
> > +config XILINX_DMA
> > +        tristate "Xilinx AXI DMA Engine"
> > +        depends on (ARCH_ZYNQ || MICROBLAZE)
> > +        select DMA_ENGINE
> > +        help
> > +          Enable support for Xilinx AXI DMA Soft IP.
> > +
> > +          This engine provides high-bandwidth direct memory access
> > +          between memory and AXI4-Stream type target peripherals.
> > +          It has two stream interfaces/channels, Memory Mapped to
> > +          Stream (MM2S) and Stream to Memory Mapped (S2MM) for the
> > +          data transfers.
> > +
> >  endif
> > diff --git a/drivers/dma/xilinx/Makefile b/drivers/dma/xilinx/Makefile
> > index 3c4e9f2..6224a49 100644
> > --- a/drivers/dma/xilinx/Makefile
> > +++ b/drivers/dma/xilinx/Makefile
> > @@ -1 +1,2 @@
> >  obj-$(CONFIG_XILINX_VDMA) += xilinx_vdma.o
> > +obj-$(CONFIG_XILINX_DMA) += xilinx_dma.o
> > diff --git a/drivers/dma/xilinx/xilinx_dma.c
> > b/drivers/dma/xilinx/xilinx_dma.c new file mode 100644 index
> > 0000000..a9be197
> > --- /dev/null
> > +++ b/drivers/dma/xilinx/xilinx_dma.c
> > @@ -0,0 +1,1179 @@
> > +/*
> > + * DMA driver for Xilinx DMA Engine
> > + *
> > + * Copyright (C) 2010 - 2015 Xilinx, Inc. All rights reserved.
> > + *
> > + * Based on the Freescale DMA driver.
> > + *
> > + * Description:
> > + *  The AXI DMA, is a soft IP, which provides high-bandwidth Direct
> > +Memory
> > + *  Access between memory and AXI4-Stream-type target peripherals. It
> > +can be
> > + *  configured to have one channel or two channels and if configured
> > +as two
> > + *  channels, one is to transmit data from memory to a device and
> > +another is
> > + *  to receive from a device.
> > + *
> > + * This 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.
> > + */
> > +
> > +#include <linux/bitops.h>
> > +#include <linux/dma/xilinx_dma.h>
> > +#include <linux/init.h>
> > +#include <linux/interrupt.h>
> > +#include <linux/io.h>
> > +#include <linux/module.h>
> > +#include <linux/of_address.h>
> > +#include <linux/of_dma.h>
> > +#include <linux/of_irq.h>
> > +#include <linux/of_platform.h>
> > +#include <linux/slab.h>
> > +
> > +#include "../dmaengine.h"
> > +
> > +/* Register Offsets */
> > +#define XILINX_DMA_REG_CONTROL         0x00
> > +#define XILINX_DMA_REG_STATUS          0x04
> > +#define XILINX_DMA_REG_CURDESC         0x08
> > +#define XILINX_DMA_REG_TAILDESC                0x10
> > +#define XILINX_DMA_REG_SRCADDR         0x18
> > +#define XILINX_DMA_REG_DSTADDR         0x20
> > +#define XILINX_DMA_REG_BTT             0x28
> > +
> > +/* Channel/Descriptor Offsets */
> > +#define XILINX_DMA_MM2S_CTRL_OFFSET    0x00
> > +#define XILINX_DMA_S2MM_CTRL_OFFSET    0x30
> > +
> > +/* General register bits definitions */
> > +#define XILINX_DMA_CR_RUNSTOP_MASK     BIT(0)
> > +#define XILINX_DMA_CR_RESET_MASK       BIT(2)
> > +
> > +#define XILINX_DMA_CR_DELAY_SHIFT      24
> > +#define XILINX_DMA_CR_COALESCE_SHIFT   16
> > +
> > +#define XILINX_DMA_CR_DELAY_MAX                GENMASK(7, 0)
> > +#define XILINX_DMA_CR_COALESCE_MAX     GENMASK(7, 0)
> > +
> > +#define XILINX_DMA_SR_HALTED_MASK      BIT(0)
> > +#define XILINX_DMA_SR_IDLE_MASK                BIT(1)
> > +
> > +#define XILINX_DMA_XR_IRQ_IOC_MASK     BIT(12)
> > +#define XILINX_DMA_XR_IRQ_DELAY_MASK   BIT(13)
> > +#define XILINX_DMA_XR_IRQ_ERROR_MASK   BIT(14)
> > +#define XILINX_DMA_XR_IRQ_ALL_MASK     GENMASK(14, 12)
> > +
> > +/* BD definitions */
> > +#define XILINX_DMA_BD_STS_ALL_MASK     GENMASK(31, 28)
> > +#define XILINX_DMA_BD_SOP              BIT(27)
> > +#define XILINX_DMA_BD_EOP              BIT(26)
> > +
> > +/* Hw specific definitions */
> > +#define XILINX_DMA_MAX_CHANS_PER_DEVICE        0x2
> > +#define XILINX_DMA_MAX_TRANS_LEN       GENMASK(22, 0)
> > +
> > +/* Delay loop counter to prevent hardware failure */
> > +#define XILINX_DMA_LOOP_COUNT          1000000
> > +
> > +/* Maximum number of Descriptors */
> > +#define XILINX_DMA_NUM_DESCS           255
> > +#define XILINX_DMA_COALESCE_MAX                255
> > +#define XILINX_DMA_NUM_APP_WORDS       5
> > +
> > +/**
> > + * struct xilinx_dma_desc_hw - Hardware Descriptor
> > + * @next_desc: Next Descriptor Pointer @0x00
> > + * @pad1: Reserved @0x04
> > + * @buf_addr: Buffer address @0x08
> > + * @pad2: Reserved @0x0C
> > + * @pad3: Reserved @0x10
> > + * @pad4: Reserved @0x14
> > + * @control: Control field @0x18
> > + * @status: Status field @0x1C
> > + * @app: APP Fields @0x20 - 0x30
> > + */
> > +struct xilinx_dma_desc_hw {
> > +       u32 next_desc;
> > +       u32 pad1;
> > +       u32 buf_addr;
> > +       u32 pad2;
> > +       u32 pad3;
> > +       u32 pad4;
> > +       u32 control;
> > +       u32 status;
> > +       u32 app[XILINX_DMA_NUM_APP_WORDS]; } __aligned(64);
> > +
> > +/**
> > + * struct xilinx_dma_tx_segment - Descriptor segment
> > + * @hw: Hardware descriptor
> > + * @node: Node in the descriptor segments list
> > + * @phys: Physical address of segment  */ struct
> > +xilinx_dma_tx_segment {
> > +       struct xilinx_dma_desc_hw hw;
> > +       struct list_head node;
> > +       dma_addr_t phys;
> > +} __aligned(64);
> > +
> > +/**
> > + * struct xilinx_dma_tx_descriptor - Per Transaction structure
> > + * @async_tx: Async transaction descriptor
> > + * @segments: TX segments list
> > + * @node: Node in the channel descriptors list
> > + * @direction: Transfer direction
> > + */
> > +struct xilinx_dma_tx_descriptor {
> > +       struct dma_async_tx_descriptor async_tx;
> > +       struct list_head segments;
> > +       struct list_head node;
> > +       enum dma_transfer_direction direction; };
> > +
> > +/**
> > + * struct xilinx_dma_chan - Driver specific DMA channel structure
> > + * @xdev: Driver specific device structure
> > + * @ctrl_offset: Control registers offset
> > + * @ctrl_reg: Control register value
> > + * @lock: Descriptor operation lock
> > + * @pending_list: Descriptors waiting
> > + * @active_list: Descriptors ready to submit
> > + * @done_list: Complete descriptors
> > + * @free_seg_list: Free descriptors
> > + * @common: DMA common channel
> > + * @seg_v: Statically allocated segments base
> > + * @seg_p: Physical allocated segments base
> > + * @dev: The dma device
> > + * @irq: Channel IRQ
> > + * @id: Channel ID
> > + * @has_sg: Support scatter transfers
> > + * @idle: Check for channel idle
> > + * @err: Channel has errors
> > + * @tasklet: Cleanup work after irq
> > + * @residue: Residue
> > + * @desc_pendingcount: Descriptor pending count  */ struct
> > +xilinx_dma_chan {
> > +       struct xilinx_dma_device *xdev;
> > +       u32 ctrl_offset;
> > +       u32 ctrl_reg;
> > +       spinlock_t lock;
> > +       struct list_head pending_list;
> > +       struct list_head done_list;
> > +       struct list_head active_list;
> > +       struct list_head free_seg_list;
> > +       struct dma_chan common;
> > +       struct xilinx_dma_tx_segment *seg_v;
> > +       dma_addr_t seg_p;
> > +       struct device *dev;
> > +       int irq;
> > +       int id;
> > +       bool has_sg;
> > +       bool idle;
> > +       int err;
> > +       struct tasklet_struct tasklet;
> > +       u32 residue;
> > +       u32 desc_pendingcount;
> > +};
> > +
> > +/**
> > + * struct xilinx_dma_device - DMA device structure
> > + * @regs: I/O mapped base address
> > + * @dev: Device Structure
> > + * @common: DMA device structure
> > + * @chan: Driver specific DMA channel
> > + * @has_sg: Specifies whether Scatter-Gather is present or not  */
> > +struct xilinx_dma_device {
> > +       void __iomem *regs;
> > +       struct device *dev;
> > +       struct dma_device common;
> > +       struct xilinx_dma_chan *chan[XILINX_DMA_MAX_CHANS_PER_DEVICE];
> > +       bool has_sg;
> > +};
> > +
> > +/* Macros */
> > +#define to_xilinx_chan(chan) \
> > +       container_of(chan, struct xilinx_dma_chan, common) #define
> > +to_dma_tx_descriptor(tx) \
> > +       container_of(tx, struct xilinx_dma_tx_descriptor, async_tx)
> > +
> > +/* IO accessors */
> > +static inline void dma_write(struct xilinx_dma_chan *chan, u32 reg,
> > +u32 value) {
> > +       iowrite32(value, chan->xdev->regs + reg);
> Any reason to not use write here?
Most of the Xilinx drivers and the VDMA driver that got up streamed Use iowrite to make consistency b/w the drivers I used the same API's.

What is the advantage we will gain by using writel instead of iowrite32?

> > +}
> > +
> > +static inline u32 dma_read(struct xilinx_dma_chan *chan, u32 reg) {
> > +       return ioread32(chan->xdev->regs + reg);
> Any reason to not use readl here?
> > +}
> > +
> > +static inline u32 dma_ctrl_read(struct xilinx_dma_chan *chan, u32
> > +reg) {
> > +       return dma_read(chan, chan->ctrl_offset + reg); }
> > +
> > +static inline void dma_ctrl_write(struct xilinx_dma_chan *chan, u32 reg,
> > +                                 u32 value) {
> > +       dma_write(chan, chan->ctrl_offset + reg, value); }
> > +
> > +/*
> > +---------------------------------------------------------------------
> > +--------
> > + * Descriptors and segments alloc and free  */
> > +
> > +/**
> > + * xilinx_dma_alloc_tx_segment - Allocate transaction segment
> > + * @chan: Driver specific dma channel
> > + *
> > + * Return: The allocated segment on success and NULL on failure.
> > + */
> > +static struct xilinx_dma_tx_segment *
> > +xilinx_dma_alloc_tx_segment(struct xilinx_dma_chan *chan) {
> > +       struct xilinx_dma_tx_segment *segment = NULL;
> > +       unsigned long flags;
> > +
> > +       spin_lock_irqsave(&chan->lock, flags);
> > +       if (!list_empty(&chan->free_seg_list)) {
> > +               segment = list_first_entry(&chan->free_seg_list,
> > +                                          struct xilinx_dma_tx_segment,
> > +                                          node);
> > +               list_del(&segment->node);
> > +       }
> > +       spin_unlock_irqrestore(&chan->lock, flags);
> > +
> > +       return segment;
> > +}
> > +
> > +/**
> > + * xilinx_dma_clean_hw_desc - Clean hardware descriptor
> > + * @hw: HW descriptor to clean
> > + */
> > +static void xilinx_dma_clean_hw_desc(struct xilinx_dma_desc_hw *hw) {
> > +       u32 next_desc = hw->next_desc;
> > +
> > +       memset(hw, 0, sizeof(struct xilinx_dma_desc_hw));
> > +
> > +       hw->next_desc = next_desc;
> > +}
> > +
> > +/**
> > + * xilinx_dma_free_tx_segment - Free transaction segment
> > + * @chan: Driver specific dma channel
> > + * @segment: dma transaction segment
> > + */
> > +static void xilinx_dma_free_tx_segment(struct xilinx_dma_chan *chan,
> > +                                      struct xilinx_dma_tx_segment
> > +*segment) {
> > +       xilinx_dma_clean_hw_desc(&segment->hw);
> > +
> > +       list_add_tail(&segment->node, &chan->free_seg_list); }
> > +
> > +/**
> > + * xilinx_dma_tx_descriptor - Allocate transaction descriptor
> > + * @chan: Driver specific dma channel
> > + *
> > + * Return: The allocated descriptor on success and NULL on failure.
> > + */
> > +static struct xilinx_dma_tx_descriptor *
> > +xilinx_dma_alloc_tx_descriptor(struct xilinx_dma_chan *chan) {
> > +       struct xilinx_dma_tx_descriptor *desc;
> > +
> > +       desc = kzalloc(sizeof(*desc), GFP_NOWAIT);
> > +       if (!desc)
> > +               return NULL;
> > +
> > +       INIT_LIST_HEAD(&desc->segments);
> > +
> > +       return desc;
> > +}
> > +
> > +/**
> > + * xilinx_dma_free_tx_descriptor - Free transaction descriptor
> > + * @chan: Driver specific dma channel
> > + * @desc: dma transaction descriptor
> > + */
> > +static void
> > +xilinx_dma_free_tx_descriptor(struct xilinx_dma_chan *chan,
> > +                             struct xilinx_dma_tx_descriptor *desc) {
> > +       struct xilinx_dma_tx_segment *segment, *next;
> > +
> > +       if (!desc)
> > +               return;
> > +
> > +       list_for_each_entry_safe(segment, next, &desc->segments, node) {
> > +               list_del(&segment->node);
> > +               xilinx_dma_free_tx_segment(chan, segment);
> > +       }
> > +
> > +       kfree(desc);
> > +}
> > +
> > +/**
> > + * xilinx_dma_alloc_chan_resources - Allocate channel resources
> > + * @dchan: DMA channel
> > + *
> > + * Return: '0' on success and failure value on error  */ static int
> > +xilinx_dma_alloc_chan_resources(struct dma_chan *dchan) {
> > +       struct xilinx_dma_chan *chan = to_xilinx_chan(dchan);
> > +       int i;
> > +
> > +       /* Allocate the buffer descriptors. */
> > +       chan->seg_v = dma_zalloc_coherent(chan->dev,
> > +                                         sizeof(*chan->seg_v) *
> > +                                         XILINX_DMA_NUM_DESCS,
> > +                                         &chan->seg_p, GFP_KERNEL);
> > +       if (!chan->seg_v) {
> > +               dev_err(chan->dev,
> > +                       "unable to allocate channel %d descriptors\n",
> > +                       chan->id);
> > +               return -ENOMEM;
> > +       }
> > +
> > +       for (i = 0; i < XILINX_DMA_NUM_DESCS; i++) {
> > +               chan->seg_v[i].hw.next_desc =
> > +                               chan->seg_p + sizeof(*chan->seg_v) *
> > +                               ((i + 1) % XILINX_DMA_NUM_DESCS);
> > +               chan->seg_v[i].phys =
> > +                               chan->seg_p + sizeof(*chan->seg_v) * i;
> > +               list_add_tail(&chan->seg_v[i].node, &chan->free_seg_list);
> > +       }
> > +
> > +       dma_cookie_init(dchan);
> > +
> > +       /* Enable interrupts */
> > +       chan->ctrl_reg |= XILINX_DMA_XR_IRQ_ALL_MASK;
> > +       dma_ctrl_write(chan, XILINX_DMA_REG_CONTROL, chan->ctrl_reg);
> > +
> > +       return 0;
> > +}
> > +
> > +/**
> > + * xilinx_dma_free_desc_list - Free descriptors list
> > + * @chan: Driver specific dma channel
> > + * @list: List to parse and delete the descriptor  */ static void
> > +xilinx_dma_free_desc_list(struct xilinx_dma_chan *chan,
> > +                                     struct list_head *list) {
> > +       struct xilinx_dma_tx_descriptor *desc, *next;
> > +
> > +       list_for_each_entry_safe(desc, next, list, node) {
> > +               list_del(&desc->node);
> > +               xilinx_dma_free_tx_descriptor(chan, desc);
> > +       }
> > +}
> > +
> > +/**
> > + * xilinx_dma_free_descriptors - Free channel descriptors
> > + * @chan: Driver specific dma channel  */ static void
> > +xilinx_dma_free_descriptors(struct xilinx_dma_chan *chan) {
> > +       unsigned long flags;
> > +
> > +       spin_lock_irqsave(&chan->lock, flags);
> > +
> > +       xilinx_dma_free_desc_list(chan, &chan->pending_list);
> > +       xilinx_dma_free_desc_list(chan, &chan->done_list);
> > +       xilinx_dma_free_desc_list(chan, &chan->active_list);
> > +
> > +       spin_unlock_irqrestore(&chan->lock, flags); }
> > +
> > +/**
> > + * xilinx_dma_free_chan_resources - Free channel resources
> > + * @dchan: DMA channel
> > + */
> > +static void xilinx_dma_free_chan_resources(struct dma_chan *dchan) {
> > +       struct xilinx_dma_chan *chan = to_xilinx_chan(dchan);
> > +
> > +       xilinx_dma_free_descriptors(chan);
> > +
> > +       dma_free_coherent(chan->dev,
> > +                         sizeof(*chan->seg_v) * XILINX_DMA_NUM_DESCS,
> > +                         chan->seg_v, chan->seg_p); }
> > +
> > +/**
> > + * xilinx_dma_chan_desc_cleanup - Clean channel descriptors
> > + * @chan: Driver specific dma channel  */ static void
> > +xilinx_dma_chan_desc_cleanup(struct xilinx_dma_chan *chan) {
> > +       struct xilinx_dma_tx_descriptor *desc;
> > +       unsigned long flags;
> > +
> > +       spin_lock_irqsave(&chan->lock, flags);
> > +
> > +       while (!list_empty(&chan->done_list)) {
> > +               dma_async_tx_callback callback;
> > +               void *callback_param;
> > +
> > +               desc = list_first_entry(&chan->done_list,
> > +                       struct xilinx_dma_tx_descriptor, node);
> > +
> > +               /* Remove from the list of running transactions */
> > +               list_del(&desc->node);
> > +
> > +               /* Run the link descriptor callback function */
> > +               callback = desc->async_tx.callback;
> > +               callback_param = desc->async_tx.callback_param;
> > +               if (callback) {
> > +                       spin_unlock_irqrestore(&chan->lock, flags);
> > +                       callback(callback_param);
> > +                       spin_lock_irqsave(&chan->lock, flags);
> > +               }
> > +
> > +               /* Run any dependencies, then free the descriptor */
> > +               dma_run_dependencies(&desc->async_tx);
> > +               xilinx_dma_free_tx_descriptor(chan, desc);
> > +       }
> > +
> > +       spin_unlock_irqrestore(&chan->lock, flags); }
> > +
> > +/**
> > + * xilinx_dma_tx_status - Get dma transaction status
> > + * @dchan: DMA channel
> > + * @cookie: Transaction identifier
> > + * @txstate: Transaction state
> > + *
> > + * Return: DMA transaction status
> > + */
> > +static enum dma_status xilinx_dma_tx_status(struct dma_chan *dchan,
> > +                                           dma_cookie_t cookie,
> > +                                           struct dma_tx_state
> > +*txstate) {
> > +       struct xilinx_dma_chan *chan = to_xilinx_chan(dchan);
> > +       struct xilinx_dma_tx_descriptor *desc;
> > +       struct xilinx_dma_tx_segment *segment;
> > +       struct xilinx_dma_desc_hw *hw;
> > +       enum dma_status ret;
> > +       unsigned long flags;
> > +       u32 residue;
> 
> While compiling this threw a residue may be used uninitialized warning, I
> suppose 0 would be a sensible default value?

Ok will fix it.

> > +
> > +       ret = dma_cookie_status(dchan, cookie, txstate);
> > +       if (ret == DMA_COMPLETE || !txstate)
> > +               return ret;
> > +
> > +       desc = list_last_entry(&chan->active_list,
> > +                              struct xilinx_dma_tx_descriptor, node);
> > +
> > +       spin_lock_irqsave(&chan->lock, flags);
> > +       if (chan->has_sg) {
> > +               while (!list_empty(&desc->segments)) {
> > +                       segment = list_first_entry(&desc->segments,
> > +                                       struct xilinx_dma_tx_segment, node);
> > +                       hw = &segment->hw;
> > +                       residue += (hw->control - hw->status) &
> > +                                  XILINX_DMA_MAX_TRANS_LEN;
> > +               }
> > +       }
> > +
> > +       chan->residue = residue;
> > +       dma_set_residue(txstate, chan->residue);
> > +       spin_unlock_irqrestore(&chan->lock, flags);
> > +
> > +       return ret;
> > +}
> > +
> > +/**
> > + * xilinx_dma_halt - Halt DMA channel
> > + * @chan: Driver specific DMA channel  */ static void
> > +xilinx_dma_halt(struct xilinx_dma_chan *chan) {
> > +       int loop = XILINX_DMA_LOOP_COUNT;
> > +
> > +       chan->ctrl_reg &= ~XILINX_DMA_CR_RUNSTOP_MASK;
> > +       dma_ctrl_write(chan, XILINX_DMA_REG_CONTROL, chan->ctrl_reg);
> > +
> > +       /* Wait for the hardware to halt */
> > +       do {
> > +               if (dma_ctrl_read(chan, XILINX_DMA_REG_STATUS) &
> > +                       XILINX_DMA_SR_HALTED_MASK)
> > +                       break;
> > +       } while (loop--);
> > +
> > +       if (!loop) {
> > +               dev_err(chan->dev, "Cannot stop channel %p: %x\n",
> > +                       chan, dma_ctrl_read(chan, XILINX_DMA_REG_STATUS));
> > +               chan->err = true;
> > +       }
> > +}
> > +
> > +/**
> > + * xilinx_dma_start - Start DMA channel
> > + * @chan: Driver specific DMA channel  */ static void
> > +xilinx_dma_start(struct xilinx_dma_chan *chan) {
> > +       int loop = XILINX_DMA_LOOP_COUNT;
> > +
> > +       chan->ctrl_reg |= XILINX_DMA_CR_RUNSTOP_MASK;
> > +       dma_ctrl_write(chan, XILINX_DMA_REG_CONTROL, chan->ctrl_reg);
> > +
> > +       /* Wait for the hardware to start */
> > +       do {
> > +               if (!dma_ctrl_read(chan, XILINX_DMA_REG_STATUS) &
> > +                       XILINX_DMA_SR_HALTED_MASK)
> > +                       break;
> > +       } while (loop--);
> Maybe use one of the readx_poll_timeout functions?

Ok will fix it.

> > +
> > +       if (!loop) {
> > +               dev_err(chan->dev, "Cannot start channel %p: %x\n",
> > +                        chan, dma_ctrl_read(chan, XILINX_DMA_REG_STATUS));
> > +               chan->err = true;
> > +       }
> > +}
> > +
> > +/**
> > + * xilinx_dma_start_transfer - Starts DMA transfer
> > + * @chan: Driver specific channel struct pointer  */ static void
> > +xilinx_dma_start_transfer(struct xilinx_dma_chan *chan) {
> > +       struct xilinx_dma_tx_descriptor *head_desc, *tail_desc;
> > +       struct xilinx_dma_tx_segment *tail_segment;
> > +
> > +       if (chan->err)
> > +               return;
> > +
> > +       if (list_empty(&chan->pending_list))
> > +               return;
> > +
> > +       if (!chan->idle)
> > +               return;
> > +
> > +       head_desc = list_first_entry(&chan->pending_list,
> > +                                    struct xilinx_dma_tx_descriptor, node);
> > +       tail_desc = list_last_entry(&chan->pending_list,
> > +                                   struct xilinx_dma_tx_descriptor, node);
> > +       tail_segment = list_last_entry(&tail_desc->segments,
> > +                                      struct xilinx_dma_tx_segment,
> > + node);
> > +
> > +       if (chan->desc_pendingcount <= XILINX_DMA_COALESCE_MAX) {
> > +               chan->ctrl_reg &= ~XILINX_DMA_CR_COALESCE_MAX;
> > +               chan->ctrl_reg |= chan->desc_pendingcount <<
> > +                                 XILINX_DMA_CR_COALESCE_SHIFT;
> > +               dma_ctrl_write(chan, XILINX_DMA_REG_CONTROL, chan->ctrl_reg);
> > +       }
> > +
> > +       if (chan->has_sg)
> > +               dma_ctrl_write(chan, XILINX_DMA_REG_CURDESC,
> > +                              head_desc->async_tx.phys);
> > +
> > +       xilinx_dma_start(chan);
> > +
> > +       if (chan->err)
> > +               return;
> > +
> > +       /* Start the transfer */
> > +       if (chan->has_sg) {
> > +               dma_ctrl_write(chan, XILINX_DMA_REG_TAILDESC,
> > +                              tail_segment->phys);
> > +       } else {
> > +               struct xilinx_dma_tx_segment *segment;
> > +               struct xilinx_dma_desc_hw *hw;
> > +
> > +               segment = list_first_entry(&head_desc->segments,
> > +                                          struct xilinx_dma_tx_segment, node);
> > +               hw = &segment->hw;
> > +
> > +               if (head_desc->direction == DMA_MEM_TO_DEV)
> > +                       dma_ctrl_write(chan, XILINX_DMA_REG_SRCADDR,
> > +                                      hw->buf_addr);
> > +               else
> > +                       dma_ctrl_write(chan, XILINX_DMA_REG_DSTADDR,
> > +                                      hw->buf_addr);
> > +
> > +               /* Start the transfer */
> > +               dma_ctrl_write(chan, XILINX_DMA_REG_BTT,
> > +                              hw->control & XILINX_DMA_MAX_TRANS_LEN);
> > +       }
> > +
> > +       list_splice_tail_init(&chan->pending_list, &chan->active_list);
> > +       chan->desc_pendingcount = 0;
> > +       chan->idle = false;
> > +}
> > +
> > +/**
> > + * xilinx_dma_issue_pending - Issue pending transactions
> > + * @dchan: DMA channel
> > + */
> > +static void xilinx_dma_issue_pending(struct dma_chan *dchan) {
> > +       struct xilinx_dma_chan *chan = to_xilinx_chan(dchan);
> > +       unsigned long flags;
> > +
> > +       spin_lock_irqsave(&chan->lock, flags);
> > +       xilinx_dma_start_transfer(chan);
> > +       spin_unlock_irqrestore(&chan->lock, flags); }
> > +
> > +/**
> > + * xilinx_dma_complete_descriptor - Mark the active descriptor as
> > +complete
> > + * @chan : xilinx DMA channel
> > + */
> > +static void xilinx_dma_complete_descriptor(struct xilinx_dma_chan
> > +*chan) {
> > +       struct xilinx_dma_tx_descriptor *desc, *next;
> > +
> > +       if (list_empty(&chan->active_list))
> > +               return;
> > +
> > +       list_for_each_entry_safe(desc, next, &chan->active_list, node) {
> > +               list_del(&desc->node);
> > +               dma_cookie_complete(&desc->async_tx);
> > +               list_add_tail(&desc->node, &chan->done_list);
> > +       }
> > +}
> > +
> > +/**
> > + * xilinx_dma_reset - Reset DMA channel
> > + * @chan: Driver specific DMA channel
> > + *
> > + * Return: '0' on success and failure value on error  */ static int
> > +xilinx_dma_chan_reset(struct xilinx_dma_chan *chan) {
> > +       int loop = XILINX_DMA_LOOP_COUNT;
> > +       u32 tmp;
> > +
> > +       chan->ctrl_reg = dma_ctrl_read(chan, XILINX_DMA_REG_CONTROL);
> > +       dma_ctrl_write(chan, XILINX_DMA_REG_CONTROL, chan->ctrl_reg |
> > +                      XILINX_DMA_CR_RESET_MASK);
> > +
> > +       tmp = dma_ctrl_read(chan, XILINX_DMA_REG_CONTROL) &
> > +             XILINX_DMA_CR_RESET_MASK;
> > +
> > +       /* Wait for the hardware to finish reset */
> > +       do {
> > +               tmp = dma_ctrl_read(chan, XILINX_DMA_REG_CONTROL) &
> > +                     XILINX_DMA_CR_RESET_MASK;
> > +       } while (loop-- && tmp);
> See above

Ok will fix it.

Regards,
Kedar.

> > +
> > +       if (!loop) {
> > +               dev_err(chan->dev, "reset timeout, cr %x, sr %x\n",
> > +                       dma_ctrl_read(chan, XILINX_DMA_REG_CONTROL),
> > +                       dma_ctrl_read(chan, XILINX_DMA_REG_STATUS));
> > +               return -EBUSY;
> > +       }
> > +
> > +       chan->err = false;
> > +
> > +       return 0;
> > +}
> > +
> > +/**
> > + * xilinx_dma_irq_handler - DMA Interrupt handler
> > + * @irq: IRQ number
> > + * @data: Pointer to the Xilinx DMA channel structure
> > + *
> > + * Return: IRQ_HANDLED/IRQ_NONE
> > + */
> > +static irqreturn_t xilinx_dma_irq_handler(int irq, void *data) {
> > +       struct xilinx_dma_chan *chan = data;
> > +       u32 status;
> > +
> > +       /* Read the status and ack the interrupts. */
> > +       status = dma_ctrl_read(chan, XILINX_DMA_REG_STATUS);
> > +       if (!(status & XILINX_DMA_XR_IRQ_ALL_MASK))
> > +               return IRQ_NONE;
> > +
> > +       dma_ctrl_write(chan, XILINX_DMA_REG_STATUS,
> > +                      status & XILINX_DMA_XR_IRQ_ALL_MASK);
> > +
> > +       if (status & XILINX_DMA_XR_IRQ_ERROR_MASK) {
> > +               dev_err(chan->dev,
> > +                       "Channel %p has errors %x, cdr %x tdr %x\n",
> > +                       chan, dma_ctrl_read(chan, XILINX_DMA_REG_STATUS),
> > +                       dma_ctrl_read(chan, XILINX_DMA_REG_CURDESC),
> > +                       dma_ctrl_read(chan, XILINX_DMA_REG_TAILDESC));
> > +               chan->err = true;
> > +       }
> > +
> > +       /*
> > +        * Device takes too long to do the transfer when user requires
> > +        * responsiveness
> > +        */
> > +       if (status & XILINX_DMA_XR_IRQ_DELAY_MASK)
> > +               dev_dbg(chan->dev, "Inter-packet latency too long\n");
> > +
> > +       if (status & XILINX_DMA_XR_IRQ_IOC_MASK) {
> > +               spin_lock(&chan->lock);
> > +               xilinx_dma_complete_descriptor(chan);
> > +               chan->idle = true;
> > +               xilinx_dma_start_transfer(chan);
> > +               spin_unlock(&chan->lock);
> > +       }
> > +
> > +       tasklet_schedule(&chan->tasklet);
> > +       return IRQ_HANDLED;
> > +}
> > +
> > +/**
> > + * xilinx_dma_do_tasklet - Schedule completion tasklet
> > + * @data: Pointer to the Xilinx dma channel structure  */ static void
> > +xilinx_dma_do_tasklet(unsigned long data) {
> > +       struct xilinx_dma_chan *chan = (struct xilinx_dma_chan *)data;
> > +
> > +       xilinx_dma_chan_desc_cleanup(chan);
> > +}
> > +
> > +/**
> > + * append_desc_queue - Queuing descriptor
> > + * @chan: Driver specific dma channel
> > + * @desc: dma transaction descriptor
> > + */
> > +static void append_desc_queue(struct xilinx_dma_chan *chan,
> > +                             struct xilinx_dma_tx_descriptor *desc) {
> > +       struct xilinx_dma_tx_segment *tail_segment;
> > +       struct xilinx_dma_tx_descriptor *tail_desc;
> > +
> > +       if (list_empty(&chan->pending_list))
> > +               goto append;
> > +
> > +       /*
> > +        * Add the hardware descriptor to the chain of hardware descriptors
> > +        * that already exists in memory.
> > +        */
> > +       tail_desc = list_last_entry(&chan->pending_list,
> > +                                   struct xilinx_dma_tx_descriptor, node);
> > +       tail_segment = list_last_entry(&tail_desc->segments,
> > +                                      struct xilinx_dma_tx_segment, node);
> > +       tail_segment->hw.next_desc = (u32)desc->async_tx.phys;
> > +
> > +       /*
> > +        * Add the software descriptor and all children to the list
> > +        * of pending transactions
> > +        */
> > +append:
> > +       list_add_tail(&desc->node, &chan->pending_list);
> > +       chan->desc_pendingcount++;
> > +
> > +       if (unlikely(chan->desc_pendingcount > XILINX_DMA_COALESCE_MAX)) {
> > +               dev_dbg(chan->dev, "desc pendingcount is too high\n");
> > +               chan->desc_pendingcount = XILINX_DMA_COALESCE_MAX;
> > +               BUG();
> > +       }
> > +}
> > +
> > +/**
> > + * xilinx_dma_tx_submit - Submit DMA transaction
> > + * @tx: Async transaction descriptor
> > + *
> > + * Return: cookie value on success and failure value on error  */
> > +static dma_cookie_t xilinx_dma_tx_submit(struct
> > +dma_async_tx_descriptor *tx) {
> > +       struct xilinx_dma_tx_descriptor *desc = to_dma_tx_descriptor(tx);
> > +       struct xilinx_dma_chan *chan = to_xilinx_chan(tx->chan);
> > +       dma_cookie_t cookie;
> > +       unsigned long flags;
> > +       int err;
> > +
> > +       if (chan->err) {
> > +               /*
> > +                * If reset fails, need to hard reset the system.
> > +                * Channel is no longer functional
> > +                */
> > +               err = xilinx_dma_chan_reset(chan);
> > +               if (err < 0)
> > +                       return err;
> > +       }
> > +
> > +       spin_lock_irqsave(&chan->lock, flags);
> > +
> > +       cookie = dma_cookie_assign(tx);
> > +
> > +       /* Put this transaction onto the tail of the pending queue */
> > +       append_desc_queue(chan, desc);
> > +
> > +       spin_unlock_irqrestore(&chan->lock, flags);
> > +
> > +       return cookie;
> > +}
> > +
> > +/**
> > + * xilinx_dma_prep_slave_sg - prepare descriptors for a DMA_SLAVE
> > +transaction
> > + * @dchan: DMA channel
> > + * @sgl: scatterlist to transfer to/from
> > + * @sg_len: number of entries in @scatterlist
> > + * @direction: DMA direction
> > + * @flags: transfer ack flags
> > + * @context: APP words of the descriptor
> > + *
> > + * Return: Async transaction descriptor on success and NULL on
> > +failure  */ static struct dma_async_tx_descriptor
> > +*xilinx_dma_prep_slave_sg(
> > +       struct dma_chan *dchan, struct scatterlist *sgl, unsigned int sg_len,
> > +       enum dma_transfer_direction direction, unsigned long flags,
> > +       void *context)
> > +{
> > +       struct xilinx_dma_chan *chan = to_xilinx_chan(dchan);
> > +       struct xilinx_dma_tx_descriptor *desc;
> > +       struct xilinx_dma_tx_segment *segment;
> > +       u32 *app_w = (u32 *)context;
> > +       struct scatterlist *sg;
> > +       size_t copy, sg_used;
> > +       int i;
> > +
> > +       if (!is_slave_direction(direction))
> > +               return NULL;
> > +
> > +       /* Allocate a transaction descriptor. */
> > +       desc = xilinx_dma_alloc_tx_descriptor(chan);
> > +       if (!desc)
> > +               return NULL;
> > +
> > +       desc->direction = direction;
> > +       dma_async_tx_descriptor_init(&desc->async_tx, &chan->common);
> > +       desc->async_tx.tx_submit = xilinx_dma_tx_submit;
> > +
> > +       /* Build transactions using information in the scatter gather list */
> > +       for_each_sg(sgl, sg, sg_len, i) {
> > +               sg_used = 0;
> > +
> > +               /* Loop until the entire scatterlist entry is used */
> > +               while (sg_used < sg_dma_len(sg)) {
> > +                       struct xilinx_dma_desc_hw *hw;
> > +
> > +                       /* Get a free segment */
> > +                       segment = xilinx_dma_alloc_tx_segment(chan);
> > +                       if (!segment)
> > +                               goto error;
> > +
> > +                       /*
> > +                        * Calculate the maximum number of bytes to transfer,
> > +                        * making sure it is less than the hw limit
> > +                        */
> > +                       copy = min_t(size_t, sg_dma_len(sg) - sg_used,
> > +                                    XILINX_DMA_MAX_TRANS_LEN);
> > +                       hw = &segment->hw;
> > +
> > +                       /* Fill in the descriptor */
> > +                       hw->buf_addr = sg_dma_address(sg) + sg_used;
> > +
> > +                       hw->control = copy;
> > +
> > +                       if (direction == DMA_MEM_TO_DEV) {
> > +                               if (app_w)
> > +                                       memcpy(hw->app, app_w, sizeof(u32) *
> > +                                              XILINX_DMA_NUM_APP_WORDS);
> > +                       }
> > +
> > +                       sg_used += copy;
> > +
> > +                       /*
> > +                        * Insert the segment into the descriptor segments
> > +                        * list.
> > +                        */
> > +                       list_add_tail(&segment->node, &desc->segments);
> > +               }
> > +       }
> > +
> > +       segment = list_first_entry(&desc->segments,
> > +                                  struct xilinx_dma_tx_segment, node);
> > +       desc->async_tx.phys = segment->phys;
> > +
> > +       /* For the last DMA_MEM_TO_DEV transfer, set EOP */
> > +       if (direction == DMA_MEM_TO_DEV) {
> > +               segment->hw.control |= XILINX_DMA_BD_SOP;
> > +               segment = list_last_entry(&desc->segments,
> > +                                         struct xilinx_dma_tx_segment,
> > +                                         node);
> > +               segment->hw.control |= XILINX_DMA_BD_EOP;
> > +       }
> > +
> > +       return &desc->async_tx;
> > +
> > +error:
> > +       xilinx_dma_free_tx_descriptor(chan, desc);
> > +       return NULL;
> > +}
> > +
> > +/**
> > + * xilinx_dma_terminate_all - Halt the channel and free descriptors
> > + * @dchan: DMA Channel pointer
> > + *
> > + * Return: '0' always
> > + */
> > +static int xilinx_dma_terminate_all(struct dma_chan *dchan) {
> > +       struct xilinx_dma_chan *chan = to_xilinx_chan(dchan);
> > +
> > +       /* Halt the DMA engine */
> > +       xilinx_dma_halt(chan);
> > +
> > +       /* Remove and free all of the descriptors in the lists */
> > +       xilinx_dma_free_descriptors(chan);
> > +
> > +       return 0;
> > +}
> > +
> > +/**
> > + * xilinx_dma_chan_remove - Per Channel remove function
> > + * @chan: Driver specific DMA channel  */ static void
> > +xilinx_dma_chan_remove(struct xilinx_dma_chan *chan) {
> > +       /* Disable interrupts */
> > +       chan->ctrl_reg &= ~XILINX_DMA_XR_IRQ_ALL_MASK;
> > +       dma_ctrl_write(chan, XILINX_DMA_REG_CONTROL, chan->ctrl_reg);
> > +
> > +       if (chan->irq > 0)
> > +               free_irq(chan->irq, chan);
> > +
> > +       tasklet_kill(&chan->tasklet);
> > +
> > +       list_del(&chan->common.device_node);
> > +}
> > +
> > +/**
> > + * xilinx_dma_chan_probe - Per Channel Probing
> > + * It get channel features from the device tree entry and
> > + * initialize special channel handling routines
> > + *
> > + * @xdev: Driver specific device structure
> > + * @node: Device node
> > + *
> > + * Return: '0' on success and failure value on error  */ static int
> > +xilinx_dma_chan_probe(struct xilinx_dma_device *xdev,
> > +                                struct device_node *node) {
> > +       struct xilinx_dma_chan *chan;
> > +       int err;
> > +       bool has_dre;
> > +       u32 value, width = 0;
> > +
> > +       /* alloc channel */
> > +       chan = devm_kzalloc(xdev->dev, sizeof(*chan), GFP_KERNEL);
> > +       if (!chan)
> > +               return -ENOMEM;
> > +
> > +       chan->dev = xdev->dev;
> > +       chan->xdev = xdev;
> > +       chan->has_sg = xdev->has_sg;
> > +       chan->desc_pendingcount = 0x0;
> > +
> > +       has_dre = of_property_read_bool(node, "xlnx,include-dre");
> > +
> > +       err = of_property_read_u32(node, "xlnx,datawidth", &value);
> > +       if (err) {
> > +               dev_err(xdev->dev, "unable to read datawidth property");
> > +               return err;
> > +       }
> > +
> > +       width = value >> 3; /* Convert bits to bytes */
> > +
> > +       /* If data width is greater than 8 bytes, DRE is not in hw */
> > +       if (width > 8)
> > +               has_dre = false;
> > +
> > +       if (!has_dre)
> > +               xdev->common.copy_align = fls(width - 1);
> > +
> > +       if (of_device_is_compatible(node, "xlnx,axi-dma-mm2s-channel")) {
> > +               chan->id = 0;
> > +               chan->ctrl_offset = XILINX_DMA_MM2S_CTRL_OFFSET;
> > +       } else if (of_device_is_compatible(node, "xlnx,axi-dma-s2mm-channel")) {
> > +               chan->id = 1;
> > +               chan->ctrl_offset = XILINX_DMA_S2MM_CTRL_OFFSET;
> > +       } else {
> > +               dev_err(xdev->dev, "Invalid channel compatible node\n");
> > +               return -EINVAL;
> > +       }
> > +
> > +       xdev->chan[chan->id] = chan;
> > +
> > +       /* Initialize the channel */
> > +       err = xilinx_dma_chan_reset(chan);
> > +       if (err) {
> > +               dev_err(xdev->dev, "Reset channel failed\n");
> > +               return err;
> > +       }
> > +
> > +       spin_lock_init(&chan->lock);
> > +       INIT_LIST_HEAD(&chan->pending_list);
> > +       INIT_LIST_HEAD(&chan->done_list);
> > +       INIT_LIST_HEAD(&chan->active_list);
> > +       INIT_LIST_HEAD(&chan->free_seg_list);
> > +
> > +       chan->common.device = &xdev->common;
> > +
> > +       /* find the IRQ line, if it exists in the device tree */
> > +       chan->irq = irq_of_parse_and_map(node, 0);
> > +       err = request_irq(chan->irq, xilinx_dma_irq_handler,
> > +                         IRQF_SHARED,
> > +                         "xilinx-dma-controller", chan);
> > +       if (err) {
> > +               dev_err(xdev->dev, "unable to request IRQ %d\n", chan->irq);
> > +               return err;
> > +       }
> > +
> > +       /* Initialize the tasklet */
> > +       tasklet_init(&chan->tasklet, xilinx_dma_do_tasklet,
> > +                    (unsigned long)chan);
> > +
> > +       /* Add the channel to DMA device channel list */
> > +       list_add_tail(&chan->common.device_node,
> > + &xdev->common.channels);
> > +
> > +       chan->idle = true;
> > +
> > +       return 0;
> > +}
> > +
> > +/**
> > + * of_dma_xilinx_xlate - Translation function
> > + * @dma_spec: Pointer to DMA specifier as found in the device tree
> > + * @ofdma: Pointer to DMA controller data
> > + *
> > + * Return: DMA channel pointer on success and NULL on error  */
> > +static struct dma_chan *of_dma_xilinx_xlate(struct of_phandle_args
> *dma_spec,
> > +                                           struct of_dma *ofdma) {
> > +       struct xilinx_dma_device *xdev = ofdma->of_dma_data;
> > +       int chan_id = dma_spec->args[0];
> > +
> > +       if (chan_id >= XILINX_DMA_MAX_CHANS_PER_DEVICE)
> > +               return NULL;
> > +
> > +       return dma_get_slave_channel(&xdev->chan[chan_id]->common);
> > +}
> > +
> > +/**
> > + * xilinx_dma_probe - Driver probe function
> > + * @pdev: Pointer to the platform_device structure
> > + *
> > + * Return: '0' on success and failure value on error  */ static int
> > +xilinx_dma_probe(struct platform_device *pdev) {
> > +       struct xilinx_dma_device *xdev;
> > +       struct device_node *child, *node;
> > +       struct resource *res;
> > +       int i, ret;
> > +
> > +       xdev = devm_kzalloc(&pdev->dev, sizeof(*xdev), GFP_KERNEL);
> > +       if (!xdev)
> > +               return -ENOMEM;
> > +
> > +       xdev->dev = &(pdev->dev);
> > +       INIT_LIST_HEAD(&xdev->common.channels);
> > +
> > +       node = pdev->dev.of_node;
> > +
> > +       /* Map the registers */
> > +       res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> > +       xdev->regs = devm_ioremap_resource(&pdev->dev, res);
> > +       if (IS_ERR(xdev->regs))
> > +               return PTR_ERR(xdev->regs);
> > +
> > +       /* Check if SG is enabled */
> > +       xdev->has_sg = of_property_read_bool(node, "xlnx,include-sg");
> > +
> > +       /* Axi DMA only do slave transfers */
> > +       dma_cap_set(DMA_SLAVE, xdev->common.cap_mask);
> > +       dma_cap_set(DMA_PRIVATE, xdev->common.cap_mask);
> > +       xdev->common.device_prep_slave_sg = xilinx_dma_prep_slave_sg;
> > +       xdev->common.device_terminate_all = xilinx_dma_terminate_all;
> > +       xdev->common.device_issue_pending = xilinx_dma_issue_pending;
> > +       xdev->common.device_alloc_chan_resources =
> > +               xilinx_dma_alloc_chan_resources;
> > +       xdev->common.device_free_chan_resources =
> > +               xilinx_dma_free_chan_resources;
> > +       xdev->common.device_tx_status = xilinx_dma_tx_status;
> > +       xdev->common.directions = BIT(DMA_DEV_TO_MEM) |
> BIT(DMA_MEM_TO_DEV);
> > +       xdev->common.residue_granularity =
> DMA_RESIDUE_GRANULARITY_SEGMENT;
> > +       xdev->common.dev = &pdev->dev;
> > +
> > +       platform_set_drvdata(pdev, xdev);
> > +
> > +       for_each_child_of_node(node, child) {
> > +               ret = xilinx_dma_chan_probe(xdev, child);
> > +               if (ret) {
> > +                       dev_err(&pdev->dev, "Probing channels failed\n");
> > +                       goto free_chan_resources;
> > +               }
> > +       }
> > +
> > +       dma_async_device_register(&xdev->common);
> > +
> > +       ret = of_dma_controller_register(node, of_dma_xilinx_xlate, xdev);
> > +       if (ret) {
> > +               dev_err(&pdev->dev, "Unable to register DMA to DT\n");
> > +               dma_async_device_unregister(&xdev->common);
> > +               goto free_chan_resources;
> > +       }
> > +
> > +       dev_info(&pdev->dev, "Xilinx AXI DMA Engine driver
> > + Probed!!\n");
> > +
> > +       return 0;
> > +
> > +free_chan_resources:
> > +       for (i = 0; i < XILINX_DMA_MAX_CHANS_PER_DEVICE; i++)
> > +               if (xdev->chan[i])
> > +                       xilinx_dma_chan_remove(xdev->chan[i]);
> > +
> > +       return ret;
> > +}
> > +
> > +/**
> > + * xilinx_dma_remove - Driver remove function
> > + * @pdev: Pointer to the platform_device structure
> > + *
> > + * Return: Always '0'
> > + */
> > +static int xilinx_dma_remove(struct platform_device *pdev) {
> > +       struct xilinx_dma_device *xdev = platform_get_drvdata(pdev);
> > +       int i;
> > +
> > +       of_dma_controller_free(pdev->dev.of_node);
> > +       dma_async_device_unregister(&xdev->common);
> > +
> > +       for (i = 0; i < XILINX_DMA_MAX_CHANS_PER_DEVICE; i++)
> > +               if (xdev->chan[i])
> > +                       xilinx_dma_chan_remove(xdev->chan[i]);
> > +
> > +       return 0;
> > +}
> > +
> > +static const struct of_device_id xilinx_dma_of_match[] = {
> > +       { .compatible = "xlnx,axi-dma-1.00.a",},
> > +       {}
> > +};
> > +MODULE_DEVICE_TABLE(of, xilinx_dma_of_match);
> > +
> > +static struct platform_driver xilinx_dma_driver = {
> > +       .driver = {
> > +               .name = "xilinx-dma",
> > +               .of_match_table = xilinx_dma_of_match,
> > +       },
> > +       .probe = xilinx_dma_probe,
> > +       .remove = xilinx_dma_remove,
> > +};
> > +
> > +module_platform_driver(xilinx_dma_driver);
> > +
> > +MODULE_AUTHOR("Xilinx, Inc.");
> > +MODULE_DESCRIPTION("Xilinx DMA driver"); MODULE_LICENSE("GPL");
> > --
> > 2.1.2
> >
> >
> > _______________________________________________
> > linux-arm-kernel mailing list
> > linux-arm-kernel@lists.infradead.org
> > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
> 
> Cheers,
> 
> Moritz
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