[PATCH] MTD: LPC32xx SLC NAND driver

STALE5205d

6 messages, 3 authors, 2012-05-15 · open the first message on its own page

[PATCH] MTD: LPC32xx SLC NAND driver

From: Roland Stigge <hidden>
Date: 2012-05-12 13:30:28

This patch adds support for the SLC NAND controller inside the LPC32xx SoC.

Signed-off-by: Roland Stigge <redacted>

---
Applies to 3.4-rc6

This driver is ported from git.lpclinux.com 2.6.39.2-lpc, including DT and
dmaengine/pl080 support.

 Documentation/devicetree/bindings/mtd/lpc32xx-slc.txt |   52 
 drivers/mtd/nand/Kconfig                              |   11 
 drivers/mtd/nand/Makefile                             |    1 
 drivers/mtd/nand/lpc32xx_nand_slc.c                   | 1067 ++++++++++++++++++
 4 files changed, 1131 insertions(+)
--- /dev/null
+++ linux-2.6/Documentation/devicetree/bindings/mtd/lpc32xx-slc.txt
@@ -0,0 +1,52 @@
+NXP LPC32xx SoC NAND SLC controller
+
+Required properties:
+- compatible: "nxp,lpc3220-slc"
+- reg: Address and size of the controller
+- nand-on-flash-bbt: Use bad block table on flash
+- gpios: GPIO specification for NAND write protect
+
+The following required properties are very controller specific. See the LPC32xx
+User Manual:
+- nxp,wdr-clks: Delay before Ready signal is tested on write (W_RDY)
+- nxp,rdr-clks: Delay before Ready signal is tested on read (R_RDY)
+(The following values are specified in Hz, to make them independent of actual
+clock speed:)
+- nxp,wwidth: Write pulse width (W_WIDTH)
+- nxp,whold: Write hold time (W_HOLD)
+- nxp,wsetup: Write setup time (W_SETUP)
+- nxp,rwidth: Read pulse width (R_WIDTH)
+- nxp,rhold: Read hold time (R_HOLD)
+- nxp,rsetup: Read setup time (R_SETUP)
+
+Optional subnodes:
+- Partitions, see Documentation/devicetree/bindings/mtd/partition.txt
+
+Example:
+
+	slc: flash at 20020000 {
+		compatible = "nxp,lpc3220-slc";
+		reg = <0x20020000 0x1000>;
+		#address-cells = <1>;
+		#size-cells = <1>;
+
+		nxp,wdr-clks = <14>;
+		nxp,wwidth = <40000000>;
+		nxp,whold = <100000000>;
+		nxp,wsetup = <100000000>;
+		nxp,rdr-clks = <14>;
+		nxp,rwidth = <40000000>;
+		nxp,rhold = <66666666>;
+		nxp,rsetup = <100000000>;
+		nand-on-flash-bbt;
+		gpios = <&gpio 5 19 1>; /* GPO_P3 19, active low */
+
+		mtd0 at 00000000 {
+			label = "phy3250-boot";
+			reg = <0x00000000 0x00064000>;
+			read-only;
+		};
+
+		...
+
+	};
--- linux-2.6.orig/drivers/mtd/nand/Kconfig
+++ linux-2.6/drivers/mtd/nand/Kconfig
@@ -414,6 +414,17 @@ config MTD_NAND_PXA3xx
 	  This enables the driver for the NAND flash device found on
 	  PXA3xx processors
 
+config MTD_NAND_SLC_LPC32XX
+	bool "NXP LPC32xx SLC Controller"
+	depends on ARCH_LPC32XX
+	help
+	  Enables support for NXP's LPC32XX SLC (i.e. for Single Level Cell
+	  chips) NAND controller. This is the default for the PHYTEC 3250
+	  reference board which contains a NAND256R3A2CZA6 chip.
+
+	  Please check the actual NAND chip connected and its support
+	  by the SLC NAND controller.
+
 config MTD_NAND_CM_X270
 	tristate "Support for NAND Flash on CM-X270 modules"
 	depends on MACH_ARMCORE
--- linux-2.6.orig/drivers/mtd/nand/Makefile
+++ linux-2.6/drivers/mtd/nand/Makefile
@@ -40,6 +40,7 @@ obj-$(CONFIG_MTD_NAND_ORION)		+= orion_n
 obj-$(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-$(CONFIG_MTD_NAND_SLC_LPC32XX)      += lpc32xx_nand_slc.o
 obj-$(CONFIG_MTD_NAND_SH_FLCTL)		+= sh_flctl.o
 obj-$(CONFIG_MTD_NAND_MXC)		+= mxc_nand.o
 obj-$(CONFIG_MTD_NAND_SOCRATES)		+= socrates_nand.o
--- /dev/null
+++ linux-2.6/drivers/mtd/nand/lpc32xx_nand_slc.c
@@ -0,0 +1,1067 @@
+/*
+ * NXP LPC32XX NAND SLC driver
+ *
+ * Authors:
+ *    Kevin Wells <kevin.wells@nxp.com>
+ *    Roland Stigge <stigge@antcom.de>
+ *
+ * Copyright (C) 2011 NXP Semiconductors
+ * Copyright (C) 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.
+ */
+
+#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/io.h>
+#include <linux/mm.h>
+#include <linux/dma-mapping.h>
+#include <linux/dmaengine.h>
+#include <linux/mtd/nand_ecc.h>
+#include <linux/gpio.h>
+#include <linux/of.h>
+#include <linux/of_mtd.h>
+#include <linux/of_gpio.h>
+#include <linux/amba/pl08x.h>
+
+#define LPC32XX_MODNAME		"lpc32xx-nand"
+
+/**********************************************************************
+* SLC NAND controller register offsets
+**********************************************************************/
+
+#define SLC_DATA(x)		(x + 0x000)
+#define SLC_ADDR(x)		(x + 0x004)
+#define SLC_CMD(x)		(x + 0x008)
+#define SLC_STOP(x)		(x + 0x00C)
+#define SLC_CTRL(x)		(x + 0x010)
+#define SLC_CFG(x)		(x + 0x014)
+#define SLC_STAT(x)		(x + 0x018)
+#define SLC_INT_STAT(x)		(x + 0x01C)
+#define SLC_IEN(x)		(x + 0x020)
+#define SLC_ISR(x)		(x + 0x024)
+#define SLC_ICR(x)		(x + 0x028)
+#define SLC_TAC(x)		(x + 0x02C)
+#define SLC_TC(x)		(x + 0x030)
+#define SLC_ECC(x)		(x + 0x034)
+#define SLC_DMA_DATA(x)		(x + 0x038)
+
+/**********************************************************************
+* slc_ctrl register definitions
+**********************************************************************/
+#define SLCCTRL_SW_RESET	(1 << 2) /* Reset the NAND controller bit */
+#define SLCCTRL_ECC_CLEAR	(1 << 1) /* Reset ECC bit */
+#define SLCCTRL_DMA_START	(1 << 0) /* Start DMA channel bit */
+
+/**********************************************************************
+* slc_cfg register definitions
+**********************************************************************/
+#define SLCCFG_CE_LOW		(1 << 5) /* Force CE low bit */
+#define SLCCFG_DMA_ECC		(1 << 4) /* Enable DMA ECC bit */
+#define SLCCFG_ECC_EN		(1 << 3) /* ECC enable bit */
+#define SLCCFG_DMA_BURST	(1 << 2) /* DMA burst bit */
+#define SLCCFG_DMA_DIR		(1 << 1) /* DMA write(0)/read(1) bit */
+#define SLCCFG_WIDTH		(1 << 0) /* External device width, 0=8bit */
+
+/**********************************************************************
+* slc_stat register definitions
+**********************************************************************/
+#define SLCSTAT_DMA_FIFO	(1 << 2) /* DMA FIFO has data bit */
+#define SLCSTAT_SLC_FIFO	(1 << 1) /* SLC FIFO has data bit */
+#define SLCSTAT_NAND_READY	(1 << 0) /* NAND device is ready bit */
+
+/**********************************************************************
+* slc_int_stat, slc_ien, slc_isr, and slc_icr register definitions
+**********************************************************************/
+#define SLCSTAT_INT_TC		(1 << 1) /* Transfer count bit */
+#define SLCSTAT_INT_RDY_EN	(1 << 0) /* Ready interrupt bit */
+
+/**********************************************************************
+* slc_tac register definitions
+**********************************************************************/
+/* Clock setting for RDY write sample wait time in 2*n clocks */
+#define SLCTAC_WDR(n)		(((n) & 0xF) << 28)
+/* Write pulse width in clock cycles, 1 to 16 clocks */
+#define SLCTAC_WWIDTH(n)	(((n) & 0xF) << 24)
+/* Write hold time of control and data signals, 1 to 16 clocks */
+#define SLCTAC_WHOLD(n)		(((n) & 0xF) << 20)
+/* Write setup time of control and data signals, 1 to 16 clocks */
+#define SLCTAC_WSETUP(n)	(((n) & 0xF) << 16)
+/* Clock setting for RDY read sample wait time in 2*n clocks */
+#define SLCTAC_RDR(n)		(((n) & 0xF) << 12)
+/* Read pulse width in clock cycles, 1 to 16 clocks */
+#define SLCTAC_RWIDTH(n)	(((n) & 0xF) << 8)
+/* Read hold time of control and data signals, 1 to 16 clocks */
+#define SLCTAC_RHOLD(n)		(((n) & 0xF) << 4)
+/* Read setup time of control and data signals, 1 to 16 clocks */
+#define SLCTAC_RSETUP(n)	(((n) & 0xF) << 0)
+
+/**********************************************************************
+* slc_ecc register definitions
+**********************************************************************/
+/* ECC line party fetch macro */
+#define SLCECC_TO_LINEPAR(n)	(((n) >> 6) & 0x7FFF)
+#define SLCECC_TO_COLPAR(n)	((n) & 0x3F)
+
+/*
+ * DMA requires storage space for the DMA local buffer and the hardware ECC
+ * storage area. The DMA local buffer is only used if DMA mapping fails
+ * during runtime.
+ */
+#define LPC32XX_DMA_DATA_SIZE		4096
+#define LPC32XX_ECC_SAVE_SIZE		((4096 / 256) * 4)
+
+/* Number of bytes used for ECC stored in NAND per 256 bytes */
+#define LPC32XX_SLC_DEV_ECC_BYTES	3
+
+/*
+ * If the NAND base clock frequency can't be fetched, this frequency will be
+ * used instead as the base. This rate is used to setup the timing registers
+ * used for NAND accesses.
+ */
+#define LPC32XX_DEF_BUS_RATE		133250000
+
+/*
+ * This timeout is used for verifying the NAND buffer has commited its
+ * FIFO to memory or FLASH, or verifying the DMA transfer has completed.
+ * The timeout is used as a count for simple polled checks of the hardware.
+ * For most hardware, the actual timeouts are much lower than this, but
+ * very slow hardware may use most of this time.
+ */
+#define LPC32XX_DMA_SIMPLE_TIMEOUT	10000
+
+/*
+ * NAND ECC Layout for small page NAND devices
+ * Note: For large and huge page devices, the default layouts are used
+ */
+static struct nand_ecclayout lpc32xx_nand_oob_16 = {
+	.eccbytes = 6,
+	.eccpos = {10, 11, 12, 13, 14, 15},
+	.oobfree = {
+		{ .offset = 0, .length = 4 },
+		{ .offset = 6, .length = 4 },
+	},
+};
+
+static u8 bbt_pattern[] = {'B', 'b', 't', '0' };
+static u8 mirror_pattern[] = {'1', 't', 'b', 'B' };
+
+/*
+ * Small page FLASH BBT descriptors, marker at offset 0, version at offset 6
+ * Note: Large page devices used the default layout
+ */
+static struct nand_bbt_descr bbt_smallpage_main_descr = {
+	.options = NAND_BBT_LASTBLOCK | NAND_BBT_CREATE | NAND_BBT_WRITE
+		| NAND_BBT_2BIT | NAND_BBT_VERSION | NAND_BBT_PERCHIP,
+	.offs =	0,
+	.len = 4,
+	.veroffs = 6,
+	.maxblocks = 4,
+	.pattern = bbt_pattern
+};
+
+static struct nand_bbt_descr bbt_smallpage_mirror_descr = {
+	.options = NAND_BBT_LASTBLOCK | NAND_BBT_CREATE | NAND_BBT_WRITE
+		| NAND_BBT_2BIT | NAND_BBT_VERSION | NAND_BBT_PERCHIP,
+	.offs =	0,
+	.len = 4,
+	.veroffs = 6,
+	.maxblocks = 4,
+	.pattern = mirror_pattern
+};
+
+/*
+ * NAND platform configuration structure
+ */
+struct lpc32xx_nand_cfg_slc {
+	u32     wdr_clks;
+	u32     wwidth;
+	u32     whold;
+	u32     wsetup;
+	u32     rdr_clks;
+	u32     rwidth;
+	u32     rhold;
+	u32     rsetup;
+	bool    use_bbt;
+	unsigned wp_gpio;
+	struct mtd_partition *parts;
+	unsigned num_parts;
+};
+
+struct lpc32xx_nand_host {
+	struct nand_chip	nand_chip;
+	struct clk		*clk;
+	struct mtd_info		mtd;
+	void __iomem		*io_base;
+	struct lpc32xx_nand_cfg_slc *ncfg;
+
+	struct completion	comp;
+	struct dma_chan		*dma_chan;
+	u32			dma_buf_len;
+	struct dma_slave_config	dma_slave_config;
+	struct scatterlist	sgl;
+
+	/*
+	 * DMA and CPU addresses of ECC work area and data buffer
+	 */
+	u32			*ecc_buf;
+	u8			*data_buf;
+	dma_addr_t		io_base_dma;
+};
+
+static void lpc32xx_nand_setup(struct lpc32xx_nand_host *host)
+{
+	u32 clkrate, tmp;
+
+	/* Reset SLC controller */
+	writel(SLCCTRL_SW_RESET, SLC_CTRL(host->io_base));
+	udelay(1000);
+
+	/* Basic setup */
+	writel(0, SLC_CFG(host->io_base));
+	writel(0, SLC_IEN(host->io_base));
+	writel((SLCSTAT_INT_TC | SLCSTAT_INT_RDY_EN),
+		SLC_ICR(host->io_base));
+
+	/* Get base clock for SLC block */
+	clkrate = clk_get_rate(host->clk);
+	if (clkrate == 0)
+		clkrate = LPC32XX_DEF_BUS_RATE;
+
+	/* Compute clock setup values */
+	tmp = SLCTAC_WDR(host->ncfg->wdr_clks) |
+		SLCTAC_WWIDTH(1 + (clkrate / host->ncfg->wwidth)) |
+		SLCTAC_WHOLD(1 + (clkrate / host->ncfg->whold)) |
+		SLCTAC_WSETUP(1 + (clkrate / host->ncfg->wsetup)) |
+		SLCTAC_RDR(host->ncfg->rdr_clks) |
+		SLCTAC_RWIDTH(1 + (clkrate / host->ncfg->rwidth)) |
+		SLCTAC_RHOLD(1 + (clkrate / host->ncfg->rhold)) |
+		SLCTAC_RSETUP(1 + (clkrate / host->ncfg->rsetup));
+	writel(tmp, SLC_TAC(host->io_base));
+}
+
+/*
+ * Hardware specific access to control lines
+ */
+static void lpc32xx_nand_cmd_ctrl(struct mtd_info *mtd, int cmd,
+	unsigned int ctrl)
+{
+	u32 tmp;
+	struct nand_chip *chip = mtd->priv;
+	struct lpc32xx_nand_host *host = chip->priv;
+
+	/* Does CE state need to be changed? */
+	tmp = readl(SLC_CFG(host->io_base));
+	if (ctrl & NAND_NCE)
+		tmp |= SLCCFG_CE_LOW;
+	else
+		tmp &= ~SLCCFG_CE_LOW;
+	writel(tmp, SLC_CFG(host->io_base));
+
+	if (cmd != NAND_CMD_NONE) {
+		if (ctrl & NAND_CLE)
+			writel(cmd, SLC_CMD(host->io_base));
+		else
+			writel(cmd, SLC_ADDR(host->io_base));
+	}
+}
+
+/*
+ * Read the Device Ready pin
+ */
+static int lpc32xx_nand_device_ready(struct mtd_info *mtd)
+{
+	struct nand_chip *chip = mtd->priv;
+	struct lpc32xx_nand_host *host = chip->priv;
+	int rdy = 0;
+
+	if ((readl(SLC_STAT(host->io_base)) & SLCSTAT_NAND_READY) != 0)
+		rdy = 1;
+
+	return rdy;
+}
+
+/*
+ * Enable NAND write protect
+ */
+static void lpc32xx_wp_enable(struct lpc32xx_nand_host *host)
+{
+	gpio_set_value(host->ncfg->wp_gpio, 0);
+}
+
+/*
+ * Disable NAND write protect
+ */
+static void lpc32xx_wp_disable(struct lpc32xx_nand_host *host)
+{
+	gpio_set_value(host->ncfg->wp_gpio, 1);
+}
+
+/*
+ * Prepares SLC for transfers with H/W ECC enabled
+ */
+static void lpc32xx_nand_ecc_enable(struct mtd_info *mtd, int mode)
+{
+	/* Hardware ECC is enabled automatically in hardware as needed */
+}
+
+/*
+ * Calculates the ECC for the data
+ */
+static int lpc32xx_nand_ecc_calculate(struct mtd_info *mtd,
+				      const unsigned char *buf,
+				      unsigned char *code)
+{
+	/*
+	 * ECC is calculated automatically in hardware during syndrome read
+	 * and write operations, so it doesn't need to be calculated here.
+	 */
+	return 0;
+}
+
+/*
+ * Read a single byte from NAND device
+ */
+static u8 lpc32xx_nand_read_byte(struct mtd_info *mtd)
+{
+	struct nand_chip *chip = mtd->priv;
+	struct lpc32xx_nand_host *host = chip->priv;
+
+	return (u8)readl(SLC_DATA(host->io_base));
+}
+
+/*
+ * Simple device read without ECC
+ */
+static void lpc32xx_nand_read_buf(struct mtd_info *mtd, u_char *buf, int len)
+{
+	struct nand_chip *chip = mtd->priv;
+	struct lpc32xx_nand_host *host = chip->priv;
+
+	/* Direct device read with no ECC */
+	while (len-- > 0)
+		*buf++ = (u8)readl(SLC_DATA(host->io_base));
+}
+
+/*
+ * Simple device write without ECC
+ */
+static void lpc32xx_nand_write_buf(struct mtd_info *mtd, const u8 *buf, int len)
+{
+	struct nand_chip *chip = mtd->priv;
+	struct lpc32xx_nand_host *host = chip->priv;
+
+	/* Direct device write with no ECC */
+	while (len-- > 0)
+		writel((u32)*buf++, SLC_DATA(host->io_base));
+}
+
+/*
+ * Verify data in buffer to data on device
+ */
+static int lpc32xx_verify_buf(struct mtd_info *mtd, const u8 *buf, int len)
+{
+	struct nand_chip *chip = mtd->priv;
+	struct lpc32xx_nand_host *host = chip->priv;
+	int i;
+
+	/* DATA register must be read as 32 bits or it will fail */
+	for (i = 0; i < len; i++) {
+		if (buf[i] != (u8)readl(SLC_DATA(host->io_base)))
+			return -EFAULT;
+	}
+
+	return 0;
+}
+
+/*
+ * Read the OOB data from the device without ECC using FIFO method
+ */
+static int lpc32xx_nand_read_oob_syndrome(struct mtd_info *mtd,
+					  struct nand_chip *chip, int page,
+					  int sndcmd)
+{
+	if (sndcmd) {
+		chip->cmdfunc(mtd, NAND_CMD_READOOB, 0, page);
+		sndcmd = 0;
+	}
+	chip->read_buf(mtd, chip->oob_poi, mtd->oobsize);
+
+	return sndcmd;
+}
+
+/*
+ * Write the OOB data to the device without ECC using FIFO method
+ */
+static int lpc32xx_nand_write_oob_syndrome(struct mtd_info *mtd,
+	struct nand_chip *chip, int page)
+{
+	int status;
+
+	chip->cmdfunc(mtd, NAND_CMD_SEQIN, mtd->writesize, page);
+	chip->write_buf(mtd, chip->oob_poi, mtd->oobsize);
+
+	/* Send command to program the OOB data */
+	chip->cmdfunc(mtd, NAND_CMD_PAGEPROG, -1, -1);
+
+	status = chip->waitfunc(mtd, chip);
+
+	return status & NAND_STATUS_FAIL ? -EIO : 0;
+}
+
+/*
+ * Fills in the ECC fields in the OOB buffer with the hardware generated ECC
+ */
+static void lpc32xx_slc_ecc_copy(u8 *spare, const u32 *ecc, int count)
+{
+	int i;
+
+	for (i = 0; i < (count * 3); i += 3) {
+		u32 ce = ecc[i / 3];
+		ce = ~(ce << 2) & 0xFFFFFF;
+		spare[i + 2] = (u8)(ce & 0xFF);
+		ce >>= 8;
+		spare[i + 1] = (u8)(ce & 0xFF);
+		ce >>= 8;
+		spare[i] = (u8)(ce & 0xFF);
+	}
+}
+
+static void lpc32xx_dma_complete_func(void *completion)
+{
+	complete(completion);
+}
+
+static int lpc32xx_xmit_dma(struct mtd_info *mtd, dma_addr_t dma,
+			    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;
+	dma_cookie_t cookie;
+
+	host->dma_slave_config.direction = dir;
+	host->dma_slave_config.src_addr = dma;
+	host->dma_slave_config.dst_addr = dma;
+	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 = 4;
+	host->dma_slave_config.dst_maxburst = 4;
+	/* DMA controller does flow control: */
+	host->dma_slave_config.device_fc = false;
+	if (dmaengine_slave_config(host->dma_chan, &host->dma_slave_config)) {
+		dev_err(mtd->dev.parent, "Failed to setup DMA slave\n");
+		return -ENXIO;
+	}
+
+	sg_init_one(&host->sgl, mem, len);
+
+	res = dma_map_sg(host->dma_chan->device->dev, &host->sgl, 1, dir);
+	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);
+	desc->callback = lpc32xx_dma_complete_func;
+	desc->callback_param = &host->comp;
+
+	cookie = dmaengine_submit(desc);
+	if (dma_submit_error(cookie)) {
+		dev_err(mtd->dev.parent, "Failed to dmaengine_submit()\n");
+		goto out1;
+	}
+	dma_async_issue_pending(host->dma_chan);
+
+	wait_for_completion_timeout(&host->comp, msecs_to_jiffies(1000));
+
+	dma_sync_sg_for_cpu(host->dma_chan->device->dev, &host->sgl, 1, dir);
+
+	return 0;
+out1:
+	dma_unmap_sg(host->dma_chan->device->dev, &host->sgl, 1, dir);
+	return -ENXIO;
+}
+
+/*
+ * DMA read/write transfers with ECC support
+ */
+static int lpc32xx_xfer(struct mtd_info *mtd, u8 *buf, int eccsubpages,
+			int read)
+{
+	struct nand_chip *chip = mtd->priv;
+	struct lpc32xx_nand_host *host = chip->priv;
+	int i, timeout, status = 0;
+	int res;
+	enum dma_transfer_direction dir =
+		read ? DMA_DEV_TO_MEM : DMA_MEM_TO_DEV;
+	u8 *dma_buf;
+	bool dma_mapped;
+
+	if ((void *)buf <= high_memory) {
+		dma_buf = buf;
+		dma_mapped = true;
+	} else {
+		dma_buf = host->data_buf;
+		dma_mapped = false;
+		if (!read)
+			memcpy(host->data_buf, buf, mtd->writesize);
+	}
+
+	if (read) {
+		writel(readl(SLC_CFG(host->io_base)) |
+		       SLCCFG_DMA_DIR | SLCCFG_ECC_EN | SLCCFG_DMA_ECC |
+		       SLCCFG_DMA_BURST, SLC_CFG(host->io_base));
+	} else {
+		writel((readl(SLC_CFG(host->io_base)) |
+			SLCCFG_ECC_EN | SLCCFG_DMA_ECC | SLCCFG_DMA_BURST) &
+		       ~SLCCFG_DMA_DIR,
+			SLC_CFG(host->io_base));
+	}
+
+	/* Clear initial ECC */
+	writel(SLCCTRL_ECC_CLEAR, SLC_CTRL(host->io_base));
+
+	/* Transfer size is data area only */
+	writel(mtd->writesize, SLC_TC(host->io_base));
+
+	/* Start transfer in the NAND controller */
+	writel(readl(SLC_CTRL(host->io_base)) | SLCCTRL_DMA_START,
+	       SLC_CTRL(host->io_base));
+
+	for (i = 0; i < chip->ecc.steps; i++) {
+		/* Data */
+		res = lpc32xx_xmit_dma(mtd, SLC_DMA_DATA(host->io_base_dma),
+				       dma_buf + i * chip->ecc.size,
+				       mtd->writesize / chip->ecc.steps, dir);
+		if (res)
+			return res;
+
+		/* Always _read_ ECC */
+		if (i == chip->ecc.steps - 1)
+			break;
+		if (!read) /* ECC availability delayed on write */
+			udelay(10);
+		res = lpc32xx_xmit_dma(mtd, SLC_ECC(host->io_base_dma),
+				       &host->ecc_buf[i], 4, DMA_DEV_TO_MEM);
+		if (res)
+			return res;
+	}
+
+	/*
+	 * The DMA is finished, but the NAND controller may still have
+	 * buffered data. Wait until all the data is sent.
+	 */
+	timeout = LPC32XX_DMA_SIMPLE_TIMEOUT;
+	while ((readl(SLC_STAT(host->io_base)) & SLCSTAT_DMA_FIFO)
+	       && (timeout > 0))
+		timeout--;
+	if (!timeout) {
+		dev_err(mtd->dev.parent, "FIFO held data too long\n");
+		status = -EIO;
+	}
+
+	/* Read last calculated ECC value */
+	if (!read)
+		udelay(10);
+	host->ecc_buf[chip->ecc.steps - 1] =
+		readl(SLC_ECC(host->io_base));
+
+	/* Flush DMA */
+	dmaengine_terminate_all(host->dma_chan);
+
+	if (readl(SLC_STAT(host->io_base)) & SLCSTAT_DMA_FIFO ||
+	    readl(SLC_TC(host->io_base))) {
+		/* Something is left in the FIFO, something is wrong */
+		dev_err(mtd->dev.parent, "DMA FIFO failure\n");
+		status = -EIO;
+	}
+
+	/* Stop DMA & HW ECC */
+	writel(readl(SLC_CTRL(host->io_base)) & ~SLCCTRL_DMA_START,
+	       SLC_CTRL(host->io_base));
+	writel(readl(SLC_CFG(host->io_base)) &
+	       ~(SLCCFG_DMA_DIR | SLCCFG_ECC_EN | SLCCFG_DMA_ECC |
+		 SLCCFG_DMA_BURST), SLC_CFG(host->io_base));
+
+	if (!dma_mapped && read)
+		memcpy(buf, host->data_buf, mtd->writesize);
+
+	return status;
+}
+
+/*
+ * Read the data and OOB data from the device, use ECC correction with the
+ * data, disable ECC for the OOB data
+ */
+static int lpc32xx_nand_read_page_syndrome(struct mtd_info *mtd,
+					   struct nand_chip *chip, u8 *buf,
+					   int page)
+{
+	struct lpc32xx_nand_host *host = chip->priv;
+	int stat, i, status;
+	u8 *oobecc, tmpecc[LPC32XX_ECC_SAVE_SIZE];
+
+	/* Issue read command */
+	chip->cmdfunc(mtd, NAND_CMD_READ0, 0, page);
+
+	/* Read data and oob, calculate ECC */
+	status = lpc32xx_xfer(mtd, buf, chip->ecc.steps, 1);
+
+	/* Get OOB data */
+	chip->read_buf(mtd, chip->oob_poi, mtd->oobsize);
+
+	/* Convert to stored ECC format */
+	lpc32xx_slc_ecc_copy(tmpecc, (u32 *) host->ecc_buf, chip->ecc.steps);
+
+	/* Pointer to ECC data retrieved from NAND spare area */
+	oobecc = chip->oob_poi + chip->ecc.layout->eccpos[0];
+
+	for (i = 0; i < chip->ecc.steps; i++) {
+		stat = chip->ecc.correct(mtd, buf, oobecc,
+					 &tmpecc[i * chip->ecc.bytes]);
+		if (stat < 0)
+			mtd->ecc_stats.failed++;
+		else
+			mtd->ecc_stats.corrected += stat;
+
+		buf += chip->ecc.size;
+		oobecc += chip->ecc.bytes;
+	}
+
+	return status;
+}
+
+/*
+ * Read the data and OOB data from the device, no ECC correction with the
+ * data or OOB data
+ */
+static int lpc32xx_nand_read_page_raw_syndrome(struct mtd_info *mtd,
+					       struct nand_chip *chip,
+					       u8 *buf, int page)
+{
+	/* Issue read command */
+	chip->cmdfunc(mtd, NAND_CMD_READ0, 0, page);
+
+	/* Raw reads can just use the FIFO interface */
+	chip->read_buf(mtd, buf, chip->ecc.size * chip->ecc.steps);
+	chip->read_buf(mtd, chip->oob_poi, mtd->oobsize);
+
+	return 0;
+}
+
+/*
+ * Write the data and OOB data to the device, use ECC with the data,
+ * disable ECC for the OOB data
+ */
+static void lpc32xx_nand_write_page_syndrome(struct mtd_info *mtd,
+					     struct nand_chip *chip,
+					     const u8 *buf)
+{
+	struct lpc32xx_nand_host *host = chip->priv;
+	u8 *pb = chip->oob_poi + chip->ecc.layout->eccpos[0];
+
+	/* Write data, calculate ECC on outbound data */
+	lpc32xx_xfer(mtd, (u8 *)buf, chip->ecc.steps, 0);
+
+	/*
+	 * The calculated ECC needs some manual work done to it before
+	 * committing it to NAND. Process the calculated ECC and place
+	 * the resultant values directly into the OOB buffer. */
+	lpc32xx_slc_ecc_copy(pb, (u32 *)host->ecc_buf, chip->ecc.steps);
+
+	/* Write ECC data to device */
+	chip->write_buf(mtd, chip->oob_poi, mtd->oobsize);
+}
+
+/*
+ * Write the data and OOB data to the device, no ECC correction with the
+ * data or OOB data
+ */
+static void lpc32xx_nand_write_page_raw_syndrome(struct mtd_info *mtd,
+						 struct nand_chip *chip,
+						 const u8 *buf)
+{
+	/* Raw writes can just use the FIFO interface */
+	chip->write_buf(mtd, buf, chip->ecc.size * chip->ecc.steps);
+	chip->write_buf(mtd, chip->oob_poi, mtd->oobsize);
+}
+
+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 NAND DMA signal is #1 */
+	if (ch->cd->min_signal == 1)
+		return true;
+	return false;
+}
+
+/*
+ * Get DMA channel and allocate DMA descriptors memory.
+ * Prepare DMA descriptors link lists
+ */
+static int lpc32xx_nand_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;
+	}
+	if (dma_set_mask(host->dma_chan->device->dev, 0xFFFFFFFF)) {
+		dev_err(mtd->dev.parent, "Failed to set dma mask\n");
+		goto out1;
+	}
+
+	return 0;
+out1:
+	dma_release_channel(host->dma_chan);
+	return -ENXIO;
+}
+
+#ifdef CONFIG_OF
+static struct lpc32xx_nand_cfg_slc *lpc32xx_parse_dt(struct device *dev)
+{
+	struct lpc32xx_nand_cfg_slc *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,wdr-clks", &pdata->wdr_clks);
+	of_property_read_u32(np, "nxp,wwidth", &pdata->wwidth);
+	of_property_read_u32(np, "nxp,whold", &pdata->whold);
+	of_property_read_u32(np, "nxp,wsetup", &pdata->wsetup);
+	of_property_read_u32(np, "nxp,rdr-clks", &pdata->rdr_clks);
+	of_property_read_u32(np, "nxp,rwidth", &pdata->rwidth);
+	of_property_read_u32(np, "nxp,rhold", &pdata->rhold);
+	of_property_read_u32(np, "nxp,rsetup", &pdata->rsetup);
+
+	if (!pdata->wdr_clks || !pdata->wwidth || !pdata->whold ||
+	    !pdata->wsetup || !pdata->rdr_clks || !pdata->rwidth ||
+	    !pdata->rhold || !pdata->rsetup) {
+		dev_err(dev, "chip parameters not specified correctly\n");
+		return NULL;
+	}
+
+	pdata->use_bbt = of_get_nand_on_flash_bbt(np);
+	pdata->wp_gpio = of_get_named_gpio_flags(np, "gpios", 0, NULL);
+
+	return pdata;
+}
+#else
+static struct lpc32xx_nand_cfg_slc *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 *chip;
+	struct resource *rc;
+	struct mtd_part_parser_data ppdata = {};
+	int res;
+
+	rc = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (rc == NULL) {
+		dev_err(&pdev->dev, "No memory resource found for device\n");
+		return -EBUSY;
+	}
+
+	/* 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;
+	}
+	host->io_base_dma = rc->start;
+
+	host->io_base = devm_request_and_ioremap(&pdev->dev, rc);
+	if (host->io_base == NULL) {
+		dev_err(&pdev->dev, "ioremap failed\n");
+		return -ENOMEM;
+	}
+
+	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 (gpio_request(host->ncfg->wp_gpio, "NAND WP")) {
+		dev_err(&pdev->dev, "GPIO not available\n");
+		return -EBUSY;
+	}
+	lpc32xx_wp_disable(host);
+
+	mtd = &host->mtd;
+	chip = &host->nand_chip;
+	chip->priv = host;
+	mtd->priv = 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 failure\n");
+		res = -ENOENT;
+		goto err_exit1;
+	}
+	clk_enable(host->clk);
+
+	/* Set NAND IO addresses and command/ready functions */
+	chip->IO_ADDR_R = SLC_DATA(host->io_base);
+	chip->IO_ADDR_W = SLC_DATA(host->io_base);
+	chip->cmd_ctrl = lpc32xx_nand_cmd_ctrl;
+	chip->dev_ready = lpc32xx_nand_device_ready;
+	chip->chip_delay = 20; /* 20us command delay time */
+
+	/* Init NAND controller */
+	lpc32xx_nand_setup(host);
+
+	platform_set_drvdata(pdev, host);
+
+	/* NAND callbacks for LPC32xx SLC hardware */
+	chip->ecc.mode = NAND_ECC_HW_SYNDROME;
+	chip->read_byte = lpc32xx_nand_read_byte;
+	chip->read_buf = lpc32xx_nand_read_buf;
+	chip->write_buf = lpc32xx_nand_write_buf;
+	chip->ecc.read_page_raw = lpc32xx_nand_read_page_raw_syndrome;
+	chip->ecc.read_page = lpc32xx_nand_read_page_syndrome;
+	chip->ecc.write_page_raw = lpc32xx_nand_write_page_raw_syndrome;
+	chip->ecc.write_page = lpc32xx_nand_write_page_syndrome;
+	chip->ecc.write_oob = lpc32xx_nand_write_oob_syndrome;
+	chip->ecc.read_oob = lpc32xx_nand_read_oob_syndrome;
+	chip->ecc.calculate = lpc32xx_nand_ecc_calculate;
+	chip->ecc.correct  = nand_correct_data;
+	chip->ecc.hwctl = lpc32xx_nand_ecc_enable;
+	chip->verify_buf = lpc32xx_verify_buf;
+
+	/*
+	 * Allocate a large enough buffer for a single huge page plus
+	 * extra space for the spare area and ECC storage area
+	 */
+	host->dma_buf_len = LPC32XX_DMA_DATA_SIZE + LPC32XX_ECC_SAVE_SIZE;
+	host->data_buf = devm_kzalloc(&pdev->dev, host->dma_buf_len,
+				      GFP_KERNEL);
+	if (host->data_buf == NULL) {
+		dev_err(&pdev->dev, "Error allocating memory\n");
+		res = -ENOMEM;
+		goto err_exit2;
+	}
+
+	res = lpc32xx_nand_dma_setup(host);
+	if (res) {
+		res = -EIO;
+		goto err_exit2;
+	}
+
+	/* Find NAND device */
+	if (nand_scan_ident(mtd, 1, NULL)) {
+		res = -ENXIO;
+		goto err_exit3;
+	}
+
+	/* OOB and ECC CPU and DMA work areas */
+	host->ecc_buf = (u32 *)(host->data_buf + LPC32XX_DMA_DATA_SIZE);
+
+	/*
+	 * Small page FLASH has a unique OOB layout, but large and huge
+	 * page FLASH use the standard layout. Small page FLASH uses a
+	 * custom BBT marker layout.
+	 */
+	if (mtd->writesize <= 512)
+		chip->ecc.layout = &lpc32xx_nand_oob_16;
+
+	/* These sizes remain the same regardless of page size */
+	chip->ecc.size = 256;
+	chip->ecc.bytes = LPC32XX_SLC_DEV_ECC_BYTES;
+	chip->ecc.prepad = chip->ecc.postpad = 0;
+
+	/* Avoid extra scan if using BBT, setup BBT support */
+	if (host->ncfg->use_bbt) {
+		chip->options |= NAND_SKIP_BBTSCAN;
+		chip->bbt_options |= NAND_BBT_USE_FLASH;
+
+		/*
+		 * Use a custom BBT marker setup for small page FLASH that
+		 * won't interfere with the ECC layout. Large and huge page
+		 * FLASH use the standard layout.
+		 */
+		if (mtd->writesize <= 512) {
+			chip->bbt_td = &bbt_smallpage_main_descr;
+			chip->bbt_md = &bbt_smallpage_mirror_descr;
+		}
+	}
+
+	/*
+	 * Fills out all the uninitialized function pointers with the defaults
+	 */
+	if (nand_scan_tail(mtd)) {
+		res = -ENXIO;
+		goto err_exit3;
+	}
+
+	/* Standard layout in FLASH for bad block tables */
+	if (host->ncfg->use_bbt) {
+		if (nand_default_bbt(mtd) < 0)
+			dev_err(&pdev->dev,
+			       "Error initializing default bad block tables\n");
+	}
+
+	mtd->name = "nxp_lpc3220_slc";
+	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_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)
+{
+	u32 tmp;
+	struct lpc32xx_nand_host *host = platform_get_drvdata(pdev);
+	struct mtd_info *mtd = &host->mtd;
+
+	nand_release(mtd);
+	dma_release_channel(host->dma_chan);
+
+	/* Force CE high */
+	tmp = readl(SLC_CTRL(host->io_base));
+	tmp &= ~SLCCFG_CE_LOW;
+	writel(tmp, SLC_CTRL(host->io_base));
+
+	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)
+{
+	u32 tmp;
+	struct lpc32xx_nand_host *host = platform_get_drvdata(pdev);
+
+	/* Force CE high */
+	tmp = readl(SLC_CTRL(host->io_base));
+	tmp &= ~SLCCFG_CE_LOW;
+	writel(tmp, SLC_CTRL(host->io_base));
+
+	/* 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-slc" },
+	{ /* 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	= LPC32XX_MODNAME,
+		.owner	= THIS_MODULE,
+		.of_match_table = of_match_ptr(lpc32xx_nand_match),
+	},
+};
+
+module_platform_driver(lpc32xx_nand_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Kevin Wells <kevin.wells@nxp.com>");
+MODULE_AUTHOR("Roland Stigge <stigge@antcom.de>");
+MODULE_DESCRIPTION("NAND driver for the NXP LPC32XX SLC controller");

Re: [PATCH] MTD: LPC32xx SLC NAND driver

From: Artem Bityutskiy <dedekind1@gmail.com>
Date: 2012-05-15 07:52:18

I am CCing few other guys who take care of several drivers which use
similar way of busy-waiting - probably you could change it?

Bastian: drivers/mtd/nand/sh_flctl.c
Lars-Peter: drivers/mtd/nand/jz4740_nand.c
Huang: drivers/mtd/nand/gpmi-nand/gpmi-lib.c
Lei Wen: drivers/mtd/nand/pxa3xx_nand.c

On Sat, 2012-05-12 at 15:29 +0200, Roland Stigge wrote:
+       /*
+        * The DMA is finished, but the NAND controller may still have
+        * buffered data. Wait until all the data is sent.
+        */
+       timeout = LPC32XX_DMA_SIMPLE_TIMEOUT;
+       while ((readl(SLC_STAT(host->io_base)) & SLCSTAT_DMA_FIFO)
+              && (timeout > 0))
+               timeout--;
+       if (!timeout) {
+               dev_err(mtd->dev.parent, "FIFO held data too long\n");
+               status = -EIO;
+       } 
I know the MTD tree is full of this, but this is bad, I think. The
timeout should be time-backed, not CPU-cycles-backed.

I do not know the best way to do this, hopefully someone in the arm list
could suggest, but the following pattern is at least better:


/* Chip reaction time timeout in milliseconds */
#define LPC32XX_DMA_TIMEOUT 100

timeout = loops_per_jiffy * msecs_to_jiffies(LPC32XX_DMA_TIMEOUT);

while ((readl(...)) && timeout-- > 0)
	cpu_relax();

if (!timeout)
	error;


So basically I turned your hard-coded iterations count into a time-based
timeout. I also used cpu_relax() which is commonly used in tight-loops
like this. Here is a piece of documentation about cpu_relax():

"
The right way to perform a busy wait is:

    while (my_variable != what_i_want)
        cpu_relax();

The cpu_relax() call can lower CPU power consumption or yield to a
hyperthreaded twin processor; it also happens to serve as a compiler
barrier, so, once again, volatile is unnecessary.  Of course, busy-
waiting is generally an anti-social act to begin with.
"

-- 
Best Regards,
Artem Bityutskiy
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Re: [PATCH] MTD: LPC32xx SLC NAND driver

From: Huang Shijie <hidden>
Date: 2012-05-15 08:11:28

? 2012?05?15? 15:55, Artem Bityutskiy ??:
I am CCing few other guys who take care of several drivers which use
similar way of busy-waiting - probably you could change it?

Bastian: drivers/mtd/nand/sh_flctl.c
Lars-Peter: drivers/mtd/nand/jz4740_nand.c
Huang: drivers/mtd/nand/gpmi-nand/gpmi-lib.c
Lei Wen: drivers/mtd/nand/pxa3xx_nand.c

On Sat, 2012-05-12 at 15:29 +0200, Roland Stigge wrote:
quoted
+       /*
+        * The DMA is finished, but the NAND controller may still have
+        * buffered data. Wait until all the data is sent.
When all the data is sent, is there an interrupt for this?


Best Regards
Huang Shijie
quoted
+        */
+       timeout = LPC32XX_DMA_SIMPLE_TIMEOUT;
+       while ((readl(SLC_STAT(host->io_base))&  SLCSTAT_DMA_FIFO)
+&&  (timeout>  0))
+               timeout--;
+       if (!timeout) {
+               dev_err(mtd->dev.parent, "FIFO held data too long\n");
+               status = -EIO;
+       }
I know the MTD tree is full of this, but this is bad, I think. The
timeout should be time-backed, not CPU-cycles-backed.

I do not know the best way to do this, hopefully someone in the arm list
could suggest, but the following pattern is at least better:


/* Chip reaction time timeout in milliseconds */
#define LPC32XX_DMA_TIMEOUT 100

timeout = loops_per_jiffy * msecs_to_jiffies(LPC32XX_DMA_TIMEOUT);

while ((readl(...))&&  timeout-->  0)
	cpu_relax();

if (!timeout)
	error;


So basically I turned your hard-coded iterations count into a time-based
timeout. I also used cpu_relax() which is commonly used in tight-loops
like this. Here is a piece of documentation about cpu_relax():

"
The right way to perform a busy wait is:

     while (my_variable != what_i_want)
         cpu_relax();

The cpu_relax() call can lower CPU power consumption or yield to a
hyperthreaded twin processor; it also happens to serve as a compiler
barrier, so, once again, volatile is unnecessary.  Of course, busy-
waiting is generally an anti-social act to begin with.
"

Re: [PATCH] MTD: LPC32xx SLC NAND driver

From: Roland Stigge <hidden>
Date: 2012-05-15 13:21:00

Hi Artem and Huang,

thank you for your feedback!

On 05/15/2012 10:15 AM, Huang Shijie wrote:
quoted
On Sat, 2012-05-12 at 15:29 +0200, Roland Stigge wrote:
quoted
+       /*
+        * The DMA is finished, but the NAND controller may still have
+        * buffered data. Wait until all the data is sent.
When all the data is sent, is there an interrupt for this?
Bad news is: No

Good news is: The previous DMA operation finished with an interrupt
which according to the manual should already corresponds to this
condition. Tests show that at this point of sampling:
quoted
quoted
+       timeout = LPC32XX_DMA_SIMPLE_TIMEOUT;
+       while ((readl(SLC_STAT(host->io_base))&  SLCSTAT_DMA_FIFO)
+&&  (timeout>  0))
+               timeout--;
... the condition is always true and always just jumps over this loop,
at least with my hardware.
quoted
/* Chip reaction time timeout in milliseconds */
#define LPC32XX_DMA_TIMEOUT 100

timeout = loops_per_jiffy * msecs_to_jiffies(LPC32XX_DMA_TIMEOUT);

while ((readl(...))&&  timeout-->  0)
    cpu_relax();
As I understand loops_per_jiffy, this loop will take much longer than
the 100 ms you defined above?

Anyway, I will keep the loop for safety reasons, add an msleep() and add
a warning, should the loop be entered _at all_.

Maybe someone from NXP can give us more insight here? Maybe the
condition check isn't necessary anymore after I ported the driver to
dmaengine (this controller is always wired together with an amba-pl080
in the LPC32xx)?

Thanks in advance,

Roland

Re: [PATCH] MTD: LPC32xx SLC NAND driver

From: Artem Bityutskiy <dedekind1@gmail.com>
Date: 2012-05-15 13:28:19

On Tue, 2012-05-15 at 15:20 +0200, Roland Stigge wrote:
quoted
quoted
while ((readl(...))&&  timeout-->  0)
    cpu_relax();
As I understand loops_per_jiffy, this loop will take much longer than
the 100 ms you defined above?
Not sure about much, but longer. The idea is that this is about the
error path so if we report -EIO with a slight delay - no problem.

-- 
Best Regards,
Artem Bityutskiy
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Re: [PATCH] MTD: LPC32xx SLC NAND driver

From: Roland Stigge <hidden>
Date: 2012-05-15 13:48:34

On 05/15/2012 03:31 PM, Artem Bityutskiy wrote:
quoted
As I understand loops_per_jiffy, this loop will take much longer
than the 100 ms you defined above?
Not sure about much, but longer. The idea is that this is about
the error path so if we report -EIO with a slight delay - no
problem.
Turned out that the condition (FIFO empty) is always true for me.
Keeping the check for safety reasons for now, doing the timeout with
msleep()s which should be (cpu-wise) "social" enough and are
unexpected anyway but do approximate the ms timeout more precisely.

Roland
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