This patch adds a driver for the MLC NAND controller of the LPC32xx SoC.
Signed-off-by: Roland Stigge <[email protected]>
Signed-off-by: Alexandre Pereira da Silva <[email protected]>
---
Applies to l2-mtd
Changes since v9:
* Adjusted to API change in l2-mtd (write function returns int now)
Changes since v8:
* Use of_get_named_gpio() instead of of_get_named_gpio_flags()
* probe() returns -EPROBE_DEFER if wp_gpio is deferred from of_get_named_gpio()
Changes since v7:
* Cleanup: Use mtd nand default functions for single byte read and write
operations
* Support more chips by removing fixed page size and calculating mlc subpages
from chip data
Changes since v6:
* Kconfig: select amba dma driver
* Make wp_gpio optional by ignoring gpio if property is missing
Changes since v5:
* Renamed: lpc32xx_nand_mlc.c -> lpc32xx_mlc.c
Changes since v4:
* This patch erroneously changed Kconfig of the _other_ NAND (SLC) driver from
"bool" to "tristate". Moved this fix to the actual SLC driver patch.
Changes since v3:
* Dropped superfluous error handling of dmaengine_submit()
* Added unmapping of dma sg buffers
Changes since v2:
* Adjusted to mtd API changes
Changes since v1:
* Factored out dmaengine_slave_config() to dma_setup() function in probe()
* Fixed dma data direction and dma transfer direction differences
* Removed dma_sync_sg_for_cpu() - not necessary due to unmap
* Removed dma_set_mask()
Thanks to Alexandre Pereira da Silva, Artem Bityutskiy and Russell King for
reviewing, testing and improvements!
.../devicetree/bindings/mtd/lpc32xx-mlc.txt | 50 ++
drivers/mtd/nand/Kconfig | 12 +
drivers/mtd/nand/Makefile | 1 +
drivers/mtd/nand/lpc32xx_mlc.c | 929 ++++++++++++++++++++
4 files changed, 992 insertions(+)
create mode 100644 Documentation/devicetree/bindings/mtd/lpc32xx-mlc.txt
create mode 100644 drivers/mtd/nand/lpc32xx_mlc.c
diff --git a/Documentation/devicetree/bindings/mtd/lpc32xx-mlc.txt b/Documentation/devicetree/bindings/mtd/lpc32xx-mlc.txt
new file mode 100644
index 0000000..d0a3725
--- /dev/null
+++ b/Documentation/devicetree/bindings/mtd/lpc32xx-mlc.txt
@@ -0,0 +1,50 @@
+NXP LPC32xx SoC NAND MLC controller
+
+Required properties:
+- compatible: "nxp,lpc3220-mlc"
+- reg: Address and size of the controller
+- interrupts: The NAND interrupt specification
+- gpios: GPIO specification for NAND write protect
+
+The following required properties are very controller specific. See the LPC32xx
+User Manual 7.5.14 MLC NAND Timing Register (the values here are specified in
+Hz, to make them independent of actual clock speed and to provide for good
+accuracy:)
+- nxp,tcea_delay: TCEA_DELAY
+- nxp,busy_delay: BUSY_DELAY
+- nxp,nand_ta: NAND_TA
+- nxp,rd_high: RD_HIGH
+- nxp,rd_low: RD_LOW
+- nxp,wr_high: WR_HIGH
+- nxp,wr_low: WR_LOW
+
+Optional subnodes:
+- Partitions, see Documentation/devicetree/bindings/mtd/partition.txt
+
+Example:
+
+ mlc: flash@200A8000 {
+ compatible = "nxp,lpc3220-mlc";
+ reg = <0x200A8000 0x11000>;
+ interrupts = <11 0>;
+ #address-cells = <1>;
+ #size-cells = <1>;
+
+ nxp,tcea-delay = <333333333>;
+ nxp,busy-delay = <10000000>;
+ nxp,nand-ta = <18181818>;
+ nxp,rd-high = <31250000>;
+ nxp,rd-low = <45454545>;
+ nxp,wr-high = <40000000>;
+ nxp,wr-low = <83333333>;
+ gpios = <&gpio 5 19 1>; /* GPO_P3 19, active low */
+
+ mtd0@00000000 {
+ label = "boot";
+ reg = <0x00000000 0x00064000>;
+ read-only;
+ };
+
+ ...
+
+ };
diff --git a/drivers/mtd/nand/Kconfig b/drivers/mtd/nand/Kconfig
index de69978..50bf667 100644
--- a/drivers/mtd/nand/Kconfig
+++ b/drivers/mtd/nand/Kconfig
@@ -425,6 +425,18 @@ config MTD_NAND_SLC_LPC32XX
Please check the actual NAND chip connected and its support
by the SLC NAND controller.
+config MTD_NAND_MLC_LPC32XX
+ tristate "NXP LPC32xx MLC Controller"
+ depends on ARCH_LPC32XX
+ select AMBA_PL08X
+ help
+ Uses the LPC32XX MLC (i.e. for Multi Level Cell chips) NAND
+ controller. This is the default for the WORK92105 controller
+ board.
+
+ Please check the actual NAND chip connected and its support
+ by the MLC NAND controller.
+
config MTD_NAND_CM_X270
tristate "Support for NAND Flash on CM-X270 modules"
depends on MACH_ARMCORE
diff --git a/drivers/mtd/nand/Makefile b/drivers/mtd/nand/Makefile
index d29a893..ddee818 100644
--- a/drivers/mtd/nand/Makefile
+++ b/drivers/mtd/nand/Makefile
@@ -41,6 +41,7 @@ obj-$(CONFIG_MTD_NAND_FSL_ELBC) += fsl_elbc_nand.o
obj-$(CONFIG_MTD_NAND_FSL_IFC) += fsl_ifc_nand.o
obj-$(CONFIG_MTD_NAND_FSL_UPM) += fsl_upm.o
obj-$(CONFIG_MTD_NAND_SLC_LPC32XX) += lpc32xx_slc.o
+obj-$(CONFIG_MTD_NAND_MLC_LPC32XX) += lpc32xx_mlc.o
obj-$(CONFIG_MTD_NAND_SH_FLCTL) += sh_flctl.o
obj-$(CONFIG_MTD_NAND_MXC) += mxc_nand.o
obj-$(CONFIG_MTD_NAND_SOCRATES) += socrates_nand.o
diff --git a/drivers/mtd/nand/lpc32xx_mlc.c b/drivers/mtd/nand/lpc32xx_mlc.c
new file mode 100644
index 0000000..cbf9783
--- /dev/null
+++ b/drivers/mtd/nand/lpc32xx_mlc.c
@@ -0,0 +1,929 @@
+/*
+ * Driver for NAND MLC Controller in LPC32xx
+ *
+ * Author: Roland Stigge <[email protected]>
+ *
+ * Copyright (C) 2011 WORK Microwave GmbH
+ * Copyright (C) 2011, 2012 Roland Stigge
+ *
+ * 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.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ *
+ * NAND Flash Controller Operation:
+ * - Read: Auto Decode
+ * - Write: Auto Encode
+ * - Tested Page Sizes: 2048, 4096
+ */
+
+#include <linux/slab.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/mtd/mtd.h>
+#include <linux/mtd/nand.h>
+#include <linux/mtd/partitions.h>
+#include <linux/clk.h>
+#include <linux/err.h>
+#include <linux/delay.h>
+#include <linux/completion.h>
+#include <linux/interrupt.h>
+#include <linux/of.h>
+#include <linux/of_mtd.h>
+#include <linux/of_gpio.h>
+#include <linux/amba/pl08x.h>
+#include <linux/io.h>
+#include <linux/mm.h>
+#include <linux/dma-mapping.h>
+#include <linux/dmaengine.h>
+#include <linux/mtd/nand_ecc.h>
+
+#define DRV_NAME "lpc32xx_mlc"
+
+/**********************************************************************
+* MLC NAND controller register offsets
+**********************************************************************/
+
+#define MLC_BUFF(x) (x + 0x00000)
+#define MLC_DATA(x) (x + 0x08000)
+#define MLC_CMD(x) (x + 0x10000)
+#define MLC_ADDR(x) (x + 0x10004)
+#define MLC_ECC_ENC_REG(x) (x + 0x10008)
+#define MLC_ECC_DEC_REG(x) (x + 0x1000C)
+#define MLC_ECC_AUTO_ENC_REG(x) (x + 0x10010)
+#define MLC_ECC_AUTO_DEC_REG(x) (x + 0x10014)
+#define MLC_RPR(x) (x + 0x10018)
+#define MLC_WPR(x) (x + 0x1001C)
+#define MLC_RUBP(x) (x + 0x10020)
+#define MLC_ROBP(x) (x + 0x10024)
+#define MLC_SW_WP_ADD_LOW(x) (x + 0x10028)
+#define MLC_SW_WP_ADD_HIG(x) (x + 0x1002C)
+#define MLC_ICR(x) (x + 0x10030)
+#define MLC_TIME_REG(x) (x + 0x10034)
+#define MLC_IRQ_MR(x) (x + 0x10038)
+#define MLC_IRQ_SR(x) (x + 0x1003C)
+#define MLC_LOCK_PR(x) (x + 0x10044)
+#define MLC_ISR(x) (x + 0x10048)
+#define MLC_CEH(x) (x + 0x1004C)
+
+/**********************************************************************
+* MLC_CMD bit definitions
+**********************************************************************/
+#define MLCCMD_RESET 0xFF
+
+/**********************************************************************
+* MLC_ICR bit definitions
+**********************************************************************/
+#define MLCICR_WPROT (1 << 3)
+#define MLCICR_LARGEBLOCK (1 << 2)
+#define MLCICR_LONGADDR (1 << 1)
+#define MLCICR_16BIT (1 << 0) /* unsupported by LPC32x0! */
+
+/**********************************************************************
+* MLC_TIME_REG bit definitions
+**********************************************************************/
+#define MLCTIMEREG_TCEA_DELAY(n) (((n) & 0x03) << 24)
+#define MLCTIMEREG_BUSY_DELAY(n) (((n) & 0x1F) << 19)
+#define MLCTIMEREG_NAND_TA(n) (((n) & 0x07) << 16)
+#define MLCTIMEREG_RD_HIGH(n) (((n) & 0x0F) << 12)
+#define MLCTIMEREG_RD_LOW(n) (((n) & 0x0F) << 8)
+#define MLCTIMEREG_WR_HIGH(n) (((n) & 0x0F) << 4)
+#define MLCTIMEREG_WR_LOW(n) (((n) & 0x0F) << 0)
+
+/**********************************************************************
+* MLC_IRQ_MR and MLC_IRQ_SR bit definitions
+**********************************************************************/
+#define MLCIRQ_NAND_READY (1 << 5)
+#define MLCIRQ_CONTROLLER_READY (1 << 4)
+#define MLCIRQ_DECODE_FAILURE (1 << 3)
+#define MLCIRQ_DECODE_ERROR (1 << 2)
+#define MLCIRQ_ECC_READY (1 << 1)
+#define MLCIRQ_WRPROT_FAULT (1 << 0)
+
+/**********************************************************************
+* MLC_LOCK_PR bit definitions
+**********************************************************************/
+#define MLCLOCKPR_MAGIC 0xA25E
+
+/**********************************************************************
+* MLC_ISR bit definitions
+**********************************************************************/
+#define MLCISR_DECODER_FAILURE (1 << 6)
+#define MLCISR_ERRORS ((1 << 4) | (1 << 5))
+#define MLCISR_ERRORS_DETECTED (1 << 3)
+#define MLCISR_ECC_READY (1 << 2)
+#define MLCISR_CONTROLLER_READY (1 << 1)
+#define MLCISR_NAND_READY (1 << 0)
+
+/**********************************************************************
+* MLC_CEH bit definitions
+**********************************************************************/
+#define MLCCEH_NORMAL (1 << 0)
+
+struct lpc32xx_nand_cfg_mlc {
+ u32 tcea_delay;
+ u32 busy_delay;
+ u32 nand_ta;
+ u32 rd_high;
+ u32 rd_low;
+ u32 wr_high;
+ u32 wr_low;
+ unsigned wp_gpio;
+ struct mtd_partition *parts;
+ unsigned num_parts;
+};
+
+static struct nand_ecclayout lpc32xx_nand_oob = {
+ .eccbytes = 40,
+ .eccpos = { 6, 7, 8, 9, 10, 11, 12, 13, 14, 15,
+ 22, 23, 24, 25, 26, 27, 28, 29, 30, 31,
+ 38, 39, 40, 41, 42, 43, 44, 45, 46, 47,
+ 54, 55, 56, 57, 58, 59, 60, 61, 62, 63 },
+ .oobfree = {
+ { .offset = 0,
+ .length = 6, },
+ { .offset = 16,
+ .length = 6, },
+ { .offset = 32,
+ .length = 6, },
+ { .offset = 48,
+ .length = 6, },
+ },
+};
+
+static struct nand_bbt_descr lpc32xx_nand_bbt = {
+ .options = NAND_BBT_ABSPAGE | NAND_BBT_2BIT | NAND_BBT_NO_OOB |
+ NAND_BBT_WRITE,
+ .pages = { 524224, 0, 0, 0, 0, 0, 0, 0 },
+};
+
+static struct nand_bbt_descr lpc32xx_nand_bbt_mirror = {
+ .options = NAND_BBT_ABSPAGE | NAND_BBT_2BIT | NAND_BBT_NO_OOB |
+ NAND_BBT_WRITE,
+ .pages = { 524160, 0, 0, 0, 0, 0, 0, 0 },
+};
+
+struct lpc32xx_nand_host {
+ struct nand_chip nand_chip;
+ struct clk *clk;
+ struct mtd_info mtd;
+ void __iomem *io_base;
+ int irq;
+ struct lpc32xx_nand_cfg_mlc *ncfg;
+ struct completion comp_nand;
+ struct completion comp_controller;
+ uint32_t llptr;
+ /*
+ * Physical addresses of ECC buffer, DMA data buffers, OOB data buffer
+ */
+ dma_addr_t oob_buf_phy;
+ /*
+ * Virtual addresses of ECC buffer, DMA data buffers, OOB data buffer
+ */
+ uint8_t *oob_buf;
+ /* Physical address of DMA base address */
+ dma_addr_t io_base_phy;
+
+ struct completion comp_dma;
+ struct dma_chan *dma_chan;
+ struct dma_slave_config dma_slave_config;
+ struct scatterlist sgl;
+ u8 *dma_buf;
+ int mlcsubpages; /* number of 512bytes-subpages */
+};
+
+/*
+ * Activate/Deactivate DMA Operation:
+ *
+ * Using the PL080 DMA Controller for transferring the 512 byte subpages
+ * instead of doing readl() / writel() in a loop slows it down significantly.
+ * Measurements via getnstimeofday() upon 512 byte subpage reads reveal:
+ *
+ * - readl() of 128 x 32 bits in a loop: ~20us
+ * - DMA read of 512 bytes (32 bit, 4...128 words bursts): ~60us
+ * - DMA read of 512 bytes (32 bit, no bursts): ~100us
+ *
+ * This applies to the transfer itself. In the DMA case: only the
+ * wait_for_completion() (DMA setup _not_ included).
+ *
+ * Note that the 512 bytes subpage transfer is done directly from/to a
+ * FIFO/buffer inside the NAND controller. Most of the time (~400-800us for a
+ * 2048 bytes page) is spent waiting for the NAND IRQ, anyway. (The NAND
+ * controller transferring data between its internal buffer to/from the NAND
+ * chip.)
+ *
+ * Therefore, using the PL080 DMA is disabled by default, for now.
+ *
+ */
+static int use_dma = 0;
+
+static void lpc32xx_nand_setup(struct lpc32xx_nand_host *host)
+{
+ u32 clkrate, tmp;
+
+ /* Reset MLC controller */
+ writel(MLCCMD_RESET, MLC_CMD(host->io_base));
+ udelay(1000);
+
+ /* Get base clock for MLC block */
+ clkrate = clk_get_rate(host->clk);
+ if (clkrate == 0)
+ clkrate = 104000000;
+
+ /* Unlock MLC_ICR
+ * (among others, will be locked again automatically) */
+ writew(MLCLOCKPR_MAGIC, MLC_LOCK_PR(host->io_base));
+
+ /* Configure MLC Controller: Large Block, 5 Byte Address */
+ tmp = MLCICR_LARGEBLOCK | MLCICR_LONGADDR;
+ writel(tmp, MLC_ICR(host->io_base));
+
+ /* Unlock MLC_TIME_REG
+ * (among others, will be locked again automatically) */
+ writew(MLCLOCKPR_MAGIC, MLC_LOCK_PR(host->io_base));
+
+ /* Compute clock setup values, see LPC and NAND manual */
+ tmp = 0;
+ tmp |= MLCTIMEREG_TCEA_DELAY(clkrate / host->ncfg->tcea_delay + 1);
+ tmp |= MLCTIMEREG_BUSY_DELAY(clkrate / host->ncfg->busy_delay + 1);
+ tmp |= MLCTIMEREG_NAND_TA(clkrate / host->ncfg->nand_ta + 1);
+ tmp |= MLCTIMEREG_RD_HIGH(clkrate / host->ncfg->rd_high + 1);
+ tmp |= MLCTIMEREG_RD_LOW(clkrate / host->ncfg->rd_low);
+ tmp |= MLCTIMEREG_WR_HIGH(clkrate / host->ncfg->wr_high + 1);
+ tmp |= MLCTIMEREG_WR_LOW(clkrate / host->ncfg->wr_low);
+ writel(tmp, MLC_TIME_REG(host->io_base));
+
+ /* Enable IRQ for CONTROLLER_READY and NAND_READY */
+ writeb(MLCIRQ_CONTROLLER_READY | MLCIRQ_NAND_READY,
+ MLC_IRQ_MR(host->io_base));
+
+ /* Normal nCE operation: nCE controlled by controller */
+ writel(MLCCEH_NORMAL, MLC_CEH(host->io_base));
+}
+
+/*
+ * Hardware specific access to control lines
+ */
+static void lpc32xx_nand_cmd_ctrl(struct mtd_info *mtd, int cmd,
+ unsigned int ctrl)
+{
+ struct nand_chip *nand_chip = mtd->priv;
+ struct lpc32xx_nand_host *host = nand_chip->priv;
+
+ if (cmd != NAND_CMD_NONE) {
+ if (ctrl & NAND_CLE)
+ writel(cmd, MLC_CMD(host->io_base));
+ else
+ writel(cmd, MLC_ADDR(host->io_base));
+ }
+}
+
+/*
+ * Read Device Ready (NAND device _and_ controller ready)
+ */
+static int lpc32xx_nand_device_ready(struct mtd_info *mtd)
+{
+ struct nand_chip *nand_chip = mtd->priv;
+ struct lpc32xx_nand_host *host = nand_chip->priv;
+
+ if ((readb(MLC_ISR(host->io_base)) &
+ (MLCISR_CONTROLLER_READY | MLCISR_NAND_READY)) ==
+ (MLCISR_CONTROLLER_READY | MLCISR_NAND_READY))
+ return 1;
+
+ return 0;
+}
+
+static irqreturn_t lpc3xxx_nand_irq(int irq, struct lpc32xx_nand_host *host)
+{
+ uint8_t sr;
+
+ /* Clear interrupt flag by reading status */
+ sr = readb(MLC_IRQ_SR(host->io_base));
+ if (sr & MLCIRQ_NAND_READY)
+ complete(&host->comp_nand);
+ if (sr & MLCIRQ_CONTROLLER_READY)
+ complete(&host->comp_controller);
+
+ return IRQ_HANDLED;
+}
+
+static int lpc32xx_waitfunc_nand(struct mtd_info *mtd, struct nand_chip *chip)
+{
+ struct lpc32xx_nand_host *host = chip->priv;
+
+ if (readb(MLC_ISR(host->io_base)) & MLCISR_NAND_READY)
+ goto exit;
+
+ wait_for_completion(&host->comp_nand);
+
+ while (!(readb(MLC_ISR(host->io_base)) & MLCISR_NAND_READY)) {
+ /* Seems to be delayed sometimes by controller */
+ dev_dbg(&mtd->dev, "Warning: NAND not ready.\n");
+ cpu_relax();
+ }
+
+exit:
+ return NAND_STATUS_READY;
+}
+
+static int lpc32xx_waitfunc_controller(struct mtd_info *mtd,
+ struct nand_chip *chip)
+{
+ struct lpc32xx_nand_host *host = chip->priv;
+
+ if (readb(MLC_ISR(host->io_base)) & MLCISR_CONTROLLER_READY)
+ goto exit;
+
+ wait_for_completion(&host->comp_controller);
+
+ while (!(readb(MLC_ISR(host->io_base)) &
+ MLCISR_CONTROLLER_READY)) {
+ dev_dbg(&mtd->dev, "Warning: Controller not ready.\n");
+ cpu_relax();
+ }
+
+exit:
+ return NAND_STATUS_READY;
+}
+
+static int lpc32xx_waitfunc(struct mtd_info *mtd, struct nand_chip *chip)
+{
+ lpc32xx_waitfunc_nand(mtd, chip);
+ lpc32xx_waitfunc_controller(mtd, chip);
+
+ return NAND_STATUS_READY;
+}
+
+/*
+ * Enable NAND write protect
+ */
+static void lpc32xx_wp_enable(struct lpc32xx_nand_host *host)
+{
+ if (gpio_is_valid(host->ncfg->wp_gpio))
+ gpio_set_value(host->ncfg->wp_gpio, 0);
+}
+
+/*
+ * Disable NAND write protect
+ */
+static void lpc32xx_wp_disable(struct lpc32xx_nand_host *host)
+{
+ if (gpio_is_valid(host->ncfg->wp_gpio))
+ gpio_set_value(host->ncfg->wp_gpio, 1);
+}
+
+static void lpc32xx_dma_complete_func(void *completion)
+{
+ complete(completion);
+}
+
+static int lpc32xx_xmit_dma(struct mtd_info *mtd, void *mem, int len,
+ enum dma_transfer_direction dir)
+{
+ struct nand_chip *chip = mtd->priv;
+ struct lpc32xx_nand_host *host = chip->priv;
+ struct dma_async_tx_descriptor *desc;
+ int flags = DMA_CTRL_ACK | DMA_PREP_INTERRUPT;
+ int res;
+
+ sg_init_one(&host->sgl, mem, len);
+
+ res = dma_map_sg(host->dma_chan->device->dev, &host->sgl, 1,
+ DMA_BIDIRECTIONAL);
+ if (res != 1) {
+ dev_err(mtd->dev.parent, "Failed to map sg list\n");
+ return -ENXIO;
+ }
+ desc = dmaengine_prep_slave_sg(host->dma_chan, &host->sgl, 1, dir,
+ flags);
+ if (!desc) {
+ dev_err(mtd->dev.parent, "Failed to prepare slave sg\n");
+ goto out1;
+ }
+
+ init_completion(&host->comp_dma);
+ desc->callback = lpc32xx_dma_complete_func;
+ desc->callback_param = &host->comp_dma;
+
+ dmaengine_submit(desc);
+ dma_async_issue_pending(host->dma_chan);
+
+ wait_for_completion_timeout(&host->comp_dma, msecs_to_jiffies(1000));
+
+ dma_unmap_sg(host->dma_chan->device->dev, &host->sgl, 1,
+ DMA_BIDIRECTIONAL);
+ return 0;
+out1:
+ dma_unmap_sg(host->dma_chan->device->dev, &host->sgl, 1,
+ DMA_BIDIRECTIONAL);
+ return -ENXIO;
+}
+
+static int lpc32xx_read_page(struct mtd_info *mtd, struct nand_chip *chip,
+ uint8_t *buf, int oob_required, int page)
+{
+ struct lpc32xx_nand_host *host = chip->priv;
+ int i, j;
+ uint8_t *oobbuf = chip->oob_poi;
+ u32 mlc_isr;
+ int res;
+ u8 *dma_buf;
+ bool dma_mapped;
+
+ if ((void *)buf <= high_memory) {
+ dma_buf = buf;
+ dma_mapped = true;
+ } else {
+ dma_buf = host->dma_buf;
+ dma_mapped = false;
+ }
+
+ /* Writing Command and Address */
+ chip->cmdfunc(mtd, NAND_CMD_READ0, 0, page);
+
+ /* For all sub-pages */
+ for (i = 0; i < host->mlcsubpages; i++) {
+ /* Start Auto Decode Command */
+ writeb(0x00, MLC_ECC_AUTO_DEC_REG(host->io_base));
+
+ /* Wait for Controller Ready */
+ lpc32xx_waitfunc_controller(mtd, chip);
+
+ /* Check ECC Error status */
+ mlc_isr = readl(MLC_ISR(host->io_base));
+ if (mlc_isr & MLCISR_DECODER_FAILURE) {
+ mtd->ecc_stats.failed++;
+ dev_warn(&mtd->dev, "%s: DECODER_FAILURE\n", __func__);
+ } else if (mlc_isr & MLCISR_ERRORS_DETECTED) {
+ mtd->ecc_stats.corrected += ((mlc_isr >> 4) & 0x3) + 1;
+ }
+
+ /* Read 512 + 16 Bytes */
+ if (use_dma) {
+ res = lpc32xx_xmit_dma(mtd, dma_buf + i * 512, 512,
+ DMA_DEV_TO_MEM);
+ if (res)
+ return res;
+ } else {
+ for (j = 0; j < (512 >> 2); j++) {
+ *((uint32_t *)(buf)) =
+ readl(MLC_BUFF(host->io_base));
+ buf += 4;
+ }
+ }
+ for (j = 0; j < (16 >> 2); j++) {
+ *((uint32_t *)(oobbuf)) =
+ readl(MLC_BUFF(host->io_base));
+ oobbuf += 4;
+ }
+ }
+
+ if (use_dma && !dma_mapped)
+ memcpy(buf, dma_buf, mtd->writesize);
+
+ return 0;
+}
+
+static int lpc32xx_write_page_lowlevel(struct mtd_info *mtd,
+ struct nand_chip *chip,
+ const uint8_t *buf, int oob_required)
+{
+ struct lpc32xx_nand_host *host = chip->priv;
+ const uint8_t *oobbuf = chip->oob_poi;
+ u8 *dma_buf;
+ int res;
+ int i, j;
+
+ if (use_dma) {
+ if ((void *)buf <= high_memory) {
+ dma_buf = (u8 *)buf;
+ } else {
+ dma_buf = host->dma_buf;
+ memcpy(dma_buf, buf, mtd->writesize);
+ }
+ }
+
+ for (i = 0; i < host->mlcsubpages; i++) {
+ /* Start Encode */
+ writeb(0x00, MLC_ECC_ENC_REG(host->io_base));
+
+ /* Write 512 + 6 Bytes to Buffer */
+ if (use_dma) {
+ res = lpc32xx_xmit_dma(mtd, dma_buf + i * 512, 512,
+ DMA_MEM_TO_DEV);
+ if (res)
+ return res;
+ } else {
+ for (j = 0; j < (512 >> 2); j++) {
+ writel(*((uint32_t *)(buf)),
+ MLC_BUFF(host->io_base));
+ buf += 4;
+ }
+ }
+ writel(*((uint32_t *)(oobbuf)), MLC_BUFF(host->io_base));
+ oobbuf += 4;
+ writew(*((uint16_t *)(oobbuf)), MLC_BUFF(host->io_base));
+ oobbuf += 12;
+
+ /* Auto Encode w/ Bit 8 = 0 (see LPC MLC Controller manual) */
+ writeb(0x00, MLC_ECC_AUTO_ENC_REG(host->io_base));
+
+ /* Wait for Controller Ready */
+ lpc32xx_waitfunc_controller(mtd, chip);
+ }
+ return 0;
+}
+
+static int lpc32xx_write_page(struct mtd_info *mtd, struct nand_chip *chip,
+ const uint8_t *buf, int oob_required, int page,
+ int cached, int raw)
+{
+ int res;
+
+ chip->cmdfunc(mtd, NAND_CMD_SEQIN, 0x00, page);
+ res = lpc32xx_write_page_lowlevel(mtd, chip, buf, oob_required);
+ chip->cmdfunc(mtd, NAND_CMD_PAGEPROG, -1, -1);
+ lpc32xx_waitfunc(mtd, chip);
+
+ return res;
+}
+
+static int lpc32xx_read_oob(struct mtd_info *mtd, struct nand_chip *chip,
+ int page)
+{
+ uint8_t buf[mtd->writesize];
+
+ /* Read whole page - necessary with MLC controller! */
+ lpc32xx_read_page(mtd, chip, buf, 1, page);
+
+ return 0;
+}
+
+static int lpc32xx_write_oob(struct mtd_info *mtd, struct nand_chip *chip,
+ int page)
+{
+ /* None, write_oob conflicts with the automatic LPC MLC ECC decoder! */
+ return 0;
+}
+
+/* Prepares MLC for transfers with H/W ECC enabled: always enabled anyway */
+static void lpc32xx_ecc_enable(struct mtd_info *mtd, int mode)
+{
+ /* Always enabled! */
+}
+
+static bool lpc32xx_dma_filter(struct dma_chan *chan, void *param)
+{
+ struct pl08x_dma_chan *ch =
+ container_of(chan, struct pl08x_dma_chan, chan);
+
+ /* In LPC32xx's PL080 DMA wiring, the MLC NAND DMA signal is #12 */
+ if (ch->cd->min_signal == 12)
+ return true;
+ return false;
+}
+
+static int lpc32xx_dma_setup(struct lpc32xx_nand_host *host)
+{
+ struct mtd_info *mtd = &host->mtd;
+ dma_cap_mask_t mask;
+
+ dma_cap_zero(mask);
+ dma_cap_set(DMA_SLAVE, mask);
+ host->dma_chan = dma_request_channel(mask, lpc32xx_dma_filter, NULL);
+ if (!host->dma_chan) {
+ dev_err(mtd->dev.parent, "Failed to request DMA channel\n");
+ return -EBUSY;
+ }
+
+ /*
+ * Set direction to a sensible value even if the dmaengine driver
+ * should ignore it. With the default (DMA_MEM_TO_MEM), the amba-pl08x
+ * driver criticizes it as "alien transfer direction".
+ */
+ host->dma_slave_config.direction = DMA_DEV_TO_MEM;
+ host->dma_slave_config.src_addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES;
+ host->dma_slave_config.dst_addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES;
+ host->dma_slave_config.src_maxburst = 128;
+ host->dma_slave_config.dst_maxburst = 128;
+ /* DMA controller does flow control: */
+ host->dma_slave_config.device_fc = false;
+ host->dma_slave_config.src_addr = MLC_BUFF(host->io_base_phy);
+ host->dma_slave_config.dst_addr = MLC_BUFF(host->io_base_phy);
+ if (dmaengine_slave_config(host->dma_chan, &host->dma_slave_config)) {
+ dev_err(mtd->dev.parent, "Failed to setup DMA slave\n");
+ goto out1;
+ }
+
+ return 0;
+out1:
+ dma_release_channel(host->dma_chan);
+ return -ENXIO;
+}
+
+#ifdef CONFIG_OF
+static struct lpc32xx_nand_cfg_mlc *lpc32xx_parse_dt(struct device *dev)
+{
+ struct lpc32xx_nand_cfg_mlc *pdata;
+ struct device_node *np = dev->of_node;
+
+ pdata = devm_kzalloc(dev, sizeof(*pdata), GFP_KERNEL);
+ if (!pdata) {
+ dev_err(dev, "could not allocate memory for platform data\n");
+ return NULL;
+ }
+
+ of_property_read_u32(np, "nxp,tcea-delay", &pdata->tcea_delay);
+ of_property_read_u32(np, "nxp,busy-delay", &pdata->busy_delay);
+ of_property_read_u32(np, "nxp,nand-ta", &pdata->nand_ta);
+ of_property_read_u32(np, "nxp,rd-high", &pdata->rd_high);
+ of_property_read_u32(np, "nxp,rd-low", &pdata->rd_low);
+ of_property_read_u32(np, "nxp,wr-high", &pdata->wr_high);
+ of_property_read_u32(np, "nxp,wr-low", &pdata->wr_low);
+
+ if (!pdata->tcea_delay || !pdata->busy_delay || !pdata->nand_ta ||
+ !pdata->rd_high || !pdata->rd_low || !pdata->wr_high ||
+ !pdata->wr_low) {
+ dev_err(dev, "chip parameters not specified correctly\n");
+ return NULL;
+ }
+
+ pdata->wp_gpio = of_get_named_gpio(np, "gpios", 0);
+
+ return pdata;
+}
+#else
+static struct lpc32xx_nand_cfg_mlc *lpc32xx_parse_dt(struct device *dev)
+{
+ return NULL;
+}
+#endif
+
+/*
+ * Probe for NAND controller
+ */
+static int __devinit lpc32xx_nand_probe(struct platform_device *pdev)
+{
+ struct lpc32xx_nand_host *host;
+ struct mtd_info *mtd;
+ struct nand_chip *nand_chip;
+ struct resource *rc;
+ int res;
+ uint8_t sr;
+ struct mtd_part_parser_data ppdata = {};
+
+ /* Allocate memory for the device structure (and zero it) */
+ host = devm_kzalloc(&pdev->dev, sizeof(*host), GFP_KERNEL);
+ if (!host) {
+ dev_err(&pdev->dev, "failed to allocate device structure.\n");
+ return -ENOMEM;
+ }
+
+ rc = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+ if (rc == NULL) {
+ dev_err(&pdev->dev, "No memory resource found for device!\r\n");
+ return -ENXIO;
+ }
+
+ host->io_base = devm_request_and_ioremap(&pdev->dev, rc);
+ if (host->io_base == NULL) {
+ dev_err(&pdev->dev, "ioremap failed\n");
+ return -EIO;
+ }
+ host->io_base_phy = rc->start;
+
+ mtd = &host->mtd;
+ nand_chip = &host->nand_chip;
+ if (pdev->dev.of_node)
+ host->ncfg = lpc32xx_parse_dt(&pdev->dev);
+ else
+ host->ncfg = pdev->dev.platform_data;
+ if (!host->ncfg) {
+ dev_err(&pdev->dev, "Missing platform data\n");
+ return -ENOENT;
+ }
+ if (host->ncfg->wp_gpio == -EPROBE_DEFER)
+ return -EPROBE_DEFER;
+ if (gpio_is_valid(host->ncfg->wp_gpio) &&
+ gpio_request(host->ncfg->wp_gpio, "NAND WP")) {
+ dev_err(&pdev->dev, "GPIO not available\n");
+ return -EBUSY;
+ }
+ lpc32xx_wp_disable(host);
+
+ nand_chip->priv = host; /* link the private data structures */
+ mtd->priv = nand_chip;
+ mtd->owner = THIS_MODULE;
+ mtd->dev.parent = &pdev->dev;
+
+ /* Get NAND clock */
+ host->clk = clk_get(&pdev->dev, NULL);
+ if (IS_ERR(host->clk)) {
+ dev_err(&pdev->dev, "Clock initialization failure\n");
+ res = -ENOENT;
+ goto err_exit1;
+ }
+ clk_enable(host->clk);
+
+ nand_chip->cmd_ctrl = lpc32xx_nand_cmd_ctrl;
+ nand_chip->dev_ready = lpc32xx_nand_device_ready;
+ nand_chip->chip_delay = 25; /* us */
+ nand_chip->IO_ADDR_R = MLC_DATA(host->io_base);
+ nand_chip->IO_ADDR_W = MLC_DATA(host->io_base);
+
+ /* Init NAND controller */
+ lpc32xx_nand_setup(host);
+
+ platform_set_drvdata(pdev, host);
+
+ /* Initialize function pointers */
+ nand_chip->ecc.hwctl = lpc32xx_ecc_enable;
+ nand_chip->ecc.read_page_raw = lpc32xx_read_page;
+ nand_chip->ecc.read_page = lpc32xx_read_page;
+ nand_chip->ecc.write_page_raw = lpc32xx_write_page_lowlevel;
+ nand_chip->ecc.write_page = lpc32xx_write_page_lowlevel;
+ nand_chip->ecc.write_oob = lpc32xx_write_oob;
+ nand_chip->ecc.read_oob = lpc32xx_read_oob;
+ nand_chip->ecc.strength = 4;
+ nand_chip->write_page = lpc32xx_write_page;
+ nand_chip->waitfunc = lpc32xx_waitfunc;
+
+ nand_chip->bbt_options = NAND_BBT_USE_FLASH | NAND_BBT_NO_OOB;
+ nand_chip->bbt_td = &lpc32xx_nand_bbt;
+ nand_chip->bbt_md = &lpc32xx_nand_bbt_mirror;
+
+ /* bitflip_threshold's default is defined as ecc_strength anyway.
+ * Unfortunately, it is set only later at add_mtd_device(). Meanwhile
+ * being 0, it causes bad block table scanning errors in
+ * nand_scan_tail(), so preparing it here. */
+ mtd->bitflip_threshold = nand_chip->ecc.strength;
+
+ res = lpc32xx_dma_setup(host);
+ if (res) {
+ res = -EIO;
+ goto err_exit2;
+ }
+
+ /*
+ * Scan to find existance of the device and
+ * Get the type of NAND device SMALL block or LARGE block
+ */
+ if (nand_scan_ident(mtd, 1, NULL)) {
+ res = -ENXIO;
+ goto err_exit3;
+ }
+
+ host->dma_buf = devm_kzalloc(&pdev->dev, mtd->writesize, GFP_KERNEL);
+ if (!host->dma_buf) {
+ dev_err(&pdev->dev, "Error allocating memory\n");
+ res = -ENOMEM;
+ goto err_exit3;
+ }
+
+ nand_chip->ecc.mode = NAND_ECC_HW;
+ nand_chip->ecc.size = mtd->writesize;
+ nand_chip->ecc.layout = &lpc32xx_nand_oob;
+ host->mlcsubpages = mtd->writesize / 512;
+
+ /* initially clear interrupt status */
+ sr = readb(MLC_IRQ_SR(host->io_base));
+
+ init_completion(&host->comp_nand);
+ init_completion(&host->comp_controller);
+
+ host->irq = platform_get_irq(pdev, 0);
+ if ((host->irq < 0) || (host->irq >= NR_IRQS)) {
+ dev_err(&pdev->dev, "failed to get platform irq\n");
+ res = -EINVAL;
+ goto err_exit3;
+ }
+
+ if (request_irq(host->irq, (irq_handler_t)&lpc3xxx_nand_irq,
+ IRQF_TRIGGER_HIGH, DRV_NAME, host)) {
+ dev_err(&pdev->dev, "Error requesting NAND IRQ\n");
+ res = -ENXIO;
+ goto err_exit3;
+ }
+
+ /*
+ * Fills out all the uninitialized function pointers with the defaults
+ * And scans for a bad block table if appropriate.
+ */
+ if (nand_scan_tail(mtd)) {
+ res = -ENXIO;
+ goto err_exit4;
+ }
+
+ mtd->name = DRV_NAME;
+
+ ppdata.of_node = pdev->dev.of_node;
+ res = mtd_device_parse_register(mtd, NULL, &ppdata, host->ncfg->parts,
+ host->ncfg->num_parts);
+ if (!res)
+ return res;
+
+ nand_release(mtd);
+
+err_exit4:
+ free_irq(host->irq, host);
+err_exit3:
+ dma_release_channel(host->dma_chan);
+err_exit2:
+ clk_disable(host->clk);
+ clk_put(host->clk);
+ platform_set_drvdata(pdev, NULL);
+err_exit1:
+ lpc32xx_wp_enable(host);
+ gpio_free(host->ncfg->wp_gpio);
+
+ return res;
+}
+
+/*
+ * Remove NAND device
+ */
+static int __devexit lpc32xx_nand_remove(struct platform_device *pdev)
+{
+ struct lpc32xx_nand_host *host = platform_get_drvdata(pdev);
+ struct mtd_info *mtd = &host->mtd;
+
+ nand_release(mtd);
+ free_irq(host->irq, host);
+ dma_release_channel(host->dma_chan);
+
+ clk_disable(host->clk);
+ clk_put(host->clk);
+ platform_set_drvdata(pdev, NULL);
+
+ lpc32xx_wp_enable(host);
+ gpio_free(host->ncfg->wp_gpio);
+
+ return 0;
+}
+
+#ifdef CONFIG_PM
+static int lpc32xx_nand_resume(struct platform_device *pdev)
+{
+ struct lpc32xx_nand_host *host = platform_get_drvdata(pdev);
+
+ /* Re-enable NAND clock */
+ clk_enable(host->clk);
+
+ /* Fresh init of NAND controller */
+ lpc32xx_nand_setup(host);
+
+ /* Disable write protect */
+ lpc32xx_wp_disable(host);
+
+ return 0;
+}
+
+static int lpc32xx_nand_suspend(struct platform_device *pdev, pm_message_t pm)
+{
+ struct lpc32xx_nand_host *host = platform_get_drvdata(pdev);
+
+ /* Enable write protect for safety */
+ lpc32xx_wp_enable(host);
+
+ /* Disable clock */
+ clk_disable(host->clk);
+ return 0;
+}
+
+#else
+#define lpc32xx_nand_resume NULL
+#define lpc32xx_nand_suspend NULL
+#endif
+
+#if defined(CONFIG_OF)
+static const struct of_device_id lpc32xx_nand_match[] = {
+ { .compatible = "nxp,lpc3220-mlc" },
+ { /* sentinel */ },
+};
+MODULE_DEVICE_TABLE(of, lpc32xx_nand_match);
+#endif
+
+static struct platform_driver lpc32xx_nand_driver = {
+ .probe = lpc32xx_nand_probe,
+ .remove = __devexit_p(lpc32xx_nand_remove),
+ .resume = lpc32xx_nand_resume,
+ .suspend = lpc32xx_nand_suspend,
+ .driver = {
+ .name = DRV_NAME,
+ .owner = THIS_MODULE,
+ .of_match_table = of_match_ptr(lpc32xx_nand_match),
+ },
+};
+
+module_platform_driver(lpc32xx_nand_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Roland Stigge <[email protected]>");
+MODULE_DESCRIPTION("NAND driver for the NXP LPC32XX MLC controller");
--
1.7.10.4
On Wed, 2012-06-27 at 23:55 +0200, Roland Stigge wrote:
> This patch adds a driver for the MLC NAND controller of the LPC32xx SoC.
>
> Signed-off-by: Roland Stigge <[email protected]>
> Signed-off-by: Alexandre Pereira da Silva <[email protected]>
> ---
Aiaiai complains like this about your patch, please, take a look:
--------------------------------------------------------------------------------
Successfully built configuration "arm-lpc32xx_defconfig,arm,arm-unknown-linux-gnueabi-", results:
--- before_patching.log
+++ after_patching.log
@@ @@
+drivers/mtd/nand/lpc32xx_mlc.c: In function 'lpc32xx_nand_probe':
+drivers/mtd/nand/lpc32xx_mlc.c:679:10: warning: variable 'sr' set but not used [-Wunused-but-set-variable]
+drivers/mtd/nand/lpc32xx_mlc.c:561:24: error: bad constant expression [sparse]
--------------------------------------------------------------------------------
checkpatch.pl has some complaints:
--------------------------------------------------------------------------------
checkpatch.pl results for patch "[PATCH] MTD: LPC32xx MLC NAND driver"
ERROR:INITIALISED_STATIC: do not initialise statics to 0 or NULL
#339: FILE: drivers/mtd/nand/lpc32xx_mlc.c:224:
+static int use_dma = 0;
total: 1 errors, 0 warnings, 1004 lines checked
--------------------------------------------------------------------------------
--
Best Regards,
Artem Bityutskiy
On Fri, Jun 29, 2012 at 9:37 AM, Artem Bityutskiy <[email protected]> wrote:
> On Wed, 2012-06-27 at 23:55 +0200, Roland Stigge wrote:
>> This patch adds a driver for the MLC NAND controller of the LPC32xx SoC.
>>
>> Signed-off-by: Roland Stigge <[email protected]>
>> Signed-off-by: Alexandre Pereira da Silva <[email protected]>
>> ---
>
> Aiaiai complains like this about your patch, please, take a look:
>
> --------------------------------------------------------------------------------
>
> Successfully built configuration "arm-lpc32xx_defconfig,arm,arm-unknown-linux-gnueabi-", results:
>
> --- before_patching.log
> +++ after_patching.log
> @@ @@
> +drivers/mtd/nand/lpc32xx_mlc.c: In function 'lpc32xx_nand_probe':
> +drivers/mtd/nand/lpc32xx_mlc.c:679:10: warning: variable 'sr' set but not used [-Wunused-but-set-variable]
> +drivers/mtd/nand/lpc32xx_mlc.c:561:24: error: bad constant expression [sparse]
This build fine here, with gcc 4.5.3
Which gcc version is he using?
> --------------------------------------------------------------------------------
>
> checkpatch.pl has some complaints:
>
> --------------------------------------------------------------------------------
>
> checkpatch.pl results for patch "[PATCH] MTD: LPC32xx MLC NAND driver"
>
> ERROR:INITIALISED_STATIC: do not initialise statics to 0 or NULL
> #339: FILE: drivers/mtd/nand/lpc32xx_mlc.c:224:
> +static int use_dma = 0;
>
> total: 1 errors, 0 warnings, 1004 lines checked
>
> --------------------------------------------------------------------------------
>
> --
> Best Regards,
> Artem Bityutskiy
On Fri, 2012-06-29 at 09:56 -0300, Alexandre Pereira da Silva wrote:
> > @@ @@
> > +drivers/mtd/nand/lpc32xx_mlc.c: In function 'lpc32xx_nand_probe':
> > +drivers/mtd/nand/lpc32xx_mlc.c:679:10: warning: variable 'sr' set but not used [-Wunused-but-set-variable]
gcc 4.6, aiaiai uses W=1 when building.
> > +drivers/mtd/nand/lpc32xx_mlc.c:561:24: error: bad constant expression [sparse]
This is sparse, not gcc.
--
Best Regards,
Artem Bityutskiy
On Fri, Jun 29, 2012 at 10:04 AM, Artem Bityutskiy <[email protected]> wrote:
> On Fri, 2012-06-29 at 09:56 -0300, Alexandre Pereira da Silva wrote:
>> > @@ @@
>> > +drivers/mtd/nand/lpc32xx_mlc.c: In function 'lpc32xx_nand_probe':
>> > +drivers/mtd/nand/lpc32xx_mlc.c:679:10: warning: variable 'sr' set but not used [-Wunused-but-set-variable]
>
> gcc 4.6, aiaiai uses W=1 when building.
>
>> > +drivers/mtd/nand/lpc32xx_mlc.c:561:24: error: bad constant expression [sparse]
>
> This is sparse, not gcc.
Does the oob area need to be ecc protected? If not I suggest to just
remove the read_oob and write_oob and let this to nand_base. I think
this is too much overhead to read 6 bytes.
Hi Artem!
Thanks for the notes!
On 29/06/12 14:37, Artem Bityutskiy wrote:
> Successfully built configuration
> "arm-lpc32xx_defconfig,arm,arm-unknown-linux-gnueabi-", results:
>
> --- before_patching.log +++ after_patching.log @@ @@
> +drivers/mtd/nand/lpc32xx_mlc.c: In function 'lpc32xx_nand_probe':
> +drivers/mtd/nand/lpc32xx_mlc.c:679:10: warning: variable 'sr' set
> but not used [-Wunused-but-set-variable]
> +drivers/mtd/nand/lpc32xx_mlc.c:561:24: error: bad constant
> expression [sparse]
This is because sparse doesn't understand this local variable:
uint8_t buf[mtd->writesize];
(but gcc does).
Are you sure we need to support sparse?
The above construction is quite convenient for this case and I'd
prefer this to allocating another buffer dynamically.
Thanks in advance,
Roland
On Sat, 2012-06-30 at 14:32 +0200, Roland Stigge wrote:
> Hi Artem!
>
> Thanks for the notes!
>
> On 29/06/12 14:37, Artem Bityutskiy wrote:
> > Successfully built configuration
> > "arm-lpc32xx_defconfig,arm,arm-unknown-linux-gnueabi-", results:
> >
> > --- before_patching.log +++ after_patching.log @@ @@
> > +drivers/mtd/nand/lpc32xx_mlc.c: In function 'lpc32xx_nand_probe':
> > +drivers/mtd/nand/lpc32xx_mlc.c:679:10: warning: variable 'sr' set
> > but not used [-Wunused-but-set-variable]
> > +drivers/mtd/nand/lpc32xx_mlc.c:561:24: error: bad constant
> > expression [sparse]
>
> This is because sparse doesn't understand this local variable:
>
> uint8_t buf[mtd->writesize];
mtd->writesize is typically 2048KiB (or even larger, there are MLCs with
4 and 8 KiB NAND page size). You cannot allocate that much on the stack,
linux kernel stack size is very small - only 8KiB, and there are people
who use even 4KiB stacks. So this have to be fixed.
> The above construction is quite convenient for this case and I'd
> prefer this to allocating another buffer dynamically.
Yes, in userspaces it is, but unfortunately in the kernel we cannot
afford allocating that much on the stack.
--
Best Regards,
Artem Bityutskiy