[PATCH v12 2/5] mtd: nand: vf610_nfc: add hardware BCH-ECC support
From: Stefan Agner
Date: Wed Sep 02 2015 - 21:07:03 EST
This adds hardware ECC support using the BCH encoder in the NFC IP.
The ECC encoder supports up to 32-bit correction by using 60 error
correction bytes. There is no sub-page ECC step, ECC is calculated
always accross the whole page (up to 2k pages).
Limitations:
- HW ECC: Only 2K page with 64+ OOB.
- HW ECC: Only 24 and 32-bit error correction implemented.
Raw writes have been tested using the generic nand_write_page_raw
implementation. However, raw reads are currently not possible
because the controller need to know whether we are going to use
the ECC mode already at NAND_CMD_READ0 command time. At this point
we do not have the information whether it is a raw read or a
regular read at driver level...
Signed-off-by: Bill Pringlemeir <bpringlemeir@xxxxxxxxx>
Signed-off-by: Stefan Agner <stefan@xxxxxxxx>
---
drivers/mtd/nand/Kconfig | 6 +-
drivers/mtd/nand/vf610_nfc.c | 203 ++++++++++++++++++++++++++++++++++++++++++-
2 files changed, 205 insertions(+), 4 deletions(-)
diff --git a/drivers/mtd/nand/Kconfig b/drivers/mtd/nand/Kconfig
index 9f9736c..ccd1158 100644
--- a/drivers/mtd/nand/Kconfig
+++ b/drivers/mtd/nand/Kconfig
@@ -466,8 +466,10 @@ config MTD_NAND_VF610_NFC
help
Enables support for NAND Flash Controller on some Freescale
processors like the VF610, MPC5125, MCF54418 or Kinetis K70.
- The driver supports a maximum 2k page size. The driver
- currently does not support hardware ECC.
+ The driver supports a maximum 2k page size. With 2k pages and
+ 64 bytes or more of OOB, hardware ECC with up to 32-bit error
+ correction is supported. Hardware ECC is only enabled through
+ device tree.
config MTD_NAND_MXC
tristate "MXC NAND support"
diff --git a/drivers/mtd/nand/vf610_nfc.c b/drivers/mtd/nand/vf610_nfc.c
index 0d76b3d1247..4513b08 100644
--- a/drivers/mtd/nand/vf610_nfc.c
+++ b/drivers/mtd/nand/vf610_nfc.c
@@ -19,8 +19,8 @@
* - Untested on MPC5125 and M54418.
* - DMA and pipelining not used.
* - 2K pages or less.
- * - No chip select, one NAND chip per controller.
- * - No hardware ECC.
+ * - HW ECC: Only 2K page with 64+ OOB.
+ * - HW ECC: Only 24 and 32-bit error correction implemented.
*/
#include <linux/module.h>
@@ -77,6 +77,8 @@
/* NFC ECC mode define */
#define ECC_BYPASS 0
+#define ECC_45_BYTE 6
+#define ECC_60_BYTE 7
/*** Register Mask and bit definitions */
@@ -129,6 +131,18 @@
#define CMD_DONE_CLEAR_BIT BIT(18)
#define IDLE_CLEAR_BIT BIT(17)
+/*
+ * ECC status - seems to consume 8 bytes (double word). The documented
+ * status byte is located in the lowest byte of the second word (which is
+ * the 4th or 7th byte depending on endianness).
+ * Calculate an offset to store the ECC status at the end of the buffer.
+ */
+#define ECC_SRAM_ADDR (PAGE_2K + OOB_MAX - 8)
+
+#define ECC_STATUS 0x4
+#define ECC_STATUS_MASK 0x80
+#define ECC_STATUS_ERR_COUNT 0x3F
+
enum vf610_nfc_alt_buf {
ALT_BUF_DATA = 0,
ALT_BUF_ID = 1,
@@ -152,10 +166,40 @@ struct vf610_nfc {
enum vf610_nfc_alt_buf alt_buf;
enum vf610_nfc_variant variant;
struct clk *clk;
+ bool use_hw_ecc;
+ u32 ecc_mode;
};
#define mtd_to_nfc(_mtd) container_of(_mtd, struct vf610_nfc, mtd)
+static struct nand_ecclayout vf610_nfc_ecc45 = {
+ .eccbytes = 45,
+ .eccpos = {19, 20, 21, 22, 23,
+ 24, 25, 26, 27, 28, 29, 30, 31,
+ 32, 33, 34, 35, 36, 37, 38, 39,
+ 40, 41, 42, 43, 44, 45, 46, 47,
+ 48, 49, 50, 51, 52, 53, 54, 55,
+ 56, 57, 58, 59, 60, 61, 62, 63},
+ .oobfree = {
+ {.offset = 2,
+ .length = 17} }
+};
+
+static struct nand_ecclayout vf610_nfc_ecc60 = {
+ .eccbytes = 60,
+ .eccpos = { 4, 5, 6, 7, 8, 9, 10, 11,
+ 12, 13, 14, 15, 16, 17, 18, 19,
+ 20, 21, 22, 23, 24, 25, 26, 27,
+ 28, 29, 30, 31, 32, 33, 34, 35,
+ 36, 37, 38, 39, 40, 41, 42, 43,
+ 44, 45, 46, 47, 48, 49, 50, 51,
+ 52, 53, 54, 55, 56, 57, 58, 59,
+ 60, 61, 62, 63 },
+ .oobfree = {
+ {.offset = 2,
+ .length = 2} }
+};
+
static inline u32 vf610_nfc_read(struct vf610_nfc *nfc, uint reg)
{
return readl(nfc->regs + reg);
@@ -297,6 +341,13 @@ static void vf610_nfc_addr_cycle(struct vf610_nfc *nfc, int column, int page)
ROW_ADDR_SHIFT, page);
}
+static inline void vf610_nfc_ecc_mode(struct vf610_nfc *nfc, int ecc_mode)
+{
+ vf610_nfc_set_field(nfc, NFC_FLASH_CONFIG,
+ CONFIG_ECC_MODE_MASK,
+ CONFIG_ECC_MODE_SHIFT, ecc_mode);
+}
+
static inline void vf610_nfc_transfer_size(struct vf610_nfc *nfc, int size)
{
vf610_nfc_write(nfc, NFC_SECTOR_SIZE, size);
@@ -315,6 +366,8 @@ static void vf610_nfc_command(struct mtd_info *mtd, unsigned command,
case NAND_CMD_SEQIN:
/* Use valid column/page from preread... */
vf610_nfc_addr_cycle(nfc, column, page);
+ nfc->buf_offset = 0;
+
/*
* SEQIN => data => PAGEPROG sequence is done by the controller
* hence we do not need to issue the command here...
@@ -325,6 +378,10 @@ static void vf610_nfc_command(struct mtd_info *mtd, unsigned command,
vf610_nfc_transfer_size(nfc, trfr_sz);
vf610_nfc_send_commands(nfc, NAND_CMD_SEQIN,
command, PROGRAM_PAGE_CMD_CODE);
+ if (nfc->use_hw_ecc)
+ vf610_nfc_ecc_mode(nfc, nfc->ecc_mode);
+ else
+ vf610_nfc_ecc_mode(nfc, ECC_BYPASS);
break;
case NAND_CMD_RESET:
@@ -339,6 +396,7 @@ static void vf610_nfc_command(struct mtd_info *mtd, unsigned command,
vf610_nfc_send_commands(nfc, NAND_CMD_READ0,
NAND_CMD_READSTART, READ_PAGE_CMD_CODE);
vf610_nfc_addr_cycle(nfc, column, page);
+ vf610_nfc_ecc_mode(nfc, ECC_BYPASS);
break;
case NAND_CMD_READ0:
@@ -347,6 +405,7 @@ static void vf610_nfc_command(struct mtd_info *mtd, unsigned command,
vf610_nfc_send_commands(nfc, NAND_CMD_READ0,
NAND_CMD_READSTART, READ_PAGE_CMD_CODE);
vf610_nfc_addr_cycle(nfc, column, page);
+ vf610_nfc_ecc_mode(nfc, nfc->ecc_mode);
break;
case NAND_CMD_PARAM:
@@ -355,6 +414,7 @@ static void vf610_nfc_command(struct mtd_info *mtd, unsigned command,
vf610_nfc_transfer_size(nfc, trfr_sz);
vf610_nfc_send_command(nfc, command, READ_ONFI_PARAM_CMD_CODE);
vf610_nfc_addr_cycle(nfc, -1, column);
+ vf610_nfc_ecc_mode(nfc, ECC_BYPASS);
break;
case NAND_CMD_ERASE1:
@@ -383,6 +443,7 @@ static void vf610_nfc_command(struct mtd_info *mtd, unsigned command,
vf610_nfc_done(nfc);
+ nfc->use_hw_ecc = false;
nfc->write_sz = 0;
}
@@ -477,6 +538,94 @@ static void vf610_nfc_select_chip(struct mtd_info *mtd, int chip)
vf610_nfc_write(nfc, NFC_ROW_ADDR, tmp);
}
+/* Count the number of 0's in buff up to max_bits */
+static inline int count_written_bits(uint8_t *buff, int size, int max_bits)
+{
+ uint32_t *buff32 = (uint32_t *)buff;
+ int k, written_bits = 0;
+
+ for (k = 0; k < (size / 4); k++) {
+ written_bits += hweight32(~buff32[k]);
+ if (unlikely(written_bits > max_bits))
+ break;
+ }
+
+ return written_bits;
+}
+
+static inline int vf610_nfc_correct_data(struct mtd_info *mtd, uint8_t *dat,
+ uint8_t *oob, int page)
+{
+ struct vf610_nfc *nfc = mtd_to_nfc(mtd);
+ u32 ecc_status_off = NFC_MAIN_AREA(0) + ECC_SRAM_ADDR + ECC_STATUS;
+ u8 ecc_status;
+ u8 ecc_count;
+ int flips;
+ int flips_threshold = nfc->chip.ecc.strength / 2;
+
+ ecc_status = vf610_nfc_read(nfc, ecc_status_off) & 0xff;
+ ecc_count = ecc_status & ECC_STATUS_ERR_COUNT;
+
+ if (!(ecc_status & ECC_STATUS_MASK))
+ return ecc_count;
+
+ /* Read OOB without ECC unit enabled */
+ vf610_nfc_command(mtd, NAND_CMD_READOOB, 0, page);
+ vf610_nfc_read_buf(mtd, oob, mtd->oobsize);
+
+ /*
+ * On an erased page, bit count (including OOB) should be zero or
+ * at least less then half of the ECC strength.
+ */
+ flips = count_written_bits(dat, nfc->chip.ecc.size, flips_threshold);
+ flips += count_written_bits(oob, mtd->oobsize, flips_threshold);
+
+ if (unlikely(flips > flips_threshold))
+ return -EINVAL;
+
+ /* Erased page. */
+ memset(dat, 0xff, nfc->chip.ecc.size);
+ memset(oob, 0xff, mtd->oobsize);
+ return flips;
+}
+
+static int vf610_nfc_read_page(struct mtd_info *mtd, struct nand_chip *chip,
+ uint8_t *buf, int oob_required, int page)
+{
+ int eccsize = chip->ecc.size;
+ int stat;
+
+ vf610_nfc_read_buf(mtd, buf, eccsize);
+ if (oob_required)
+ vf610_nfc_read_buf(mtd, chip->oob_poi, mtd->oobsize);
+
+ stat = vf610_nfc_correct_data(mtd, buf, chip->oob_poi, page);
+
+ if (stat < 0) {
+ mtd->ecc_stats.failed++;
+ return 0;
+ } else {
+ mtd->ecc_stats.corrected += stat;
+ return stat;
+ }
+}
+
+static int vf610_nfc_write_page(struct mtd_info *mtd, struct nand_chip *chip,
+ const uint8_t *buf, int oob_required)
+{
+ struct vf610_nfc *nfc = mtd_to_nfc(mtd);
+
+ vf610_nfc_write_buf(mtd, buf, mtd->writesize);
+ if (oob_required)
+ vf610_nfc_write_buf(mtd, chip->oob_poi, mtd->oobsize);
+
+ /* Always write whole page including OOB due to HW ECC */
+ nfc->use_hw_ecc = true;
+ nfc->write_sz = mtd->writesize + mtd->oobsize;
+
+ return 0;
+}
+
static const struct of_device_id vf610_nfc_dt_ids[] = {
{ .compatible = "fsl,vf610-nfc", .data = (void *)NFC_VFC610 },
{ /* sentinel */ }
@@ -503,6 +652,17 @@ static void vf610_nfc_init_controller(struct vf610_nfc *nfc)
vf610_nfc_set(nfc, NFC_FLASH_CONFIG, CONFIG_16BIT);
else
vf610_nfc_clear(nfc, NFC_FLASH_CONFIG, CONFIG_16BIT);
+
+ if (nfc->chip.ecc.mode == NAND_ECC_HW) {
+ /* Set ECC status offset in SRAM */
+ vf610_nfc_set_field(nfc, NFC_FLASH_CONFIG,
+ CONFIG_ECC_SRAM_ADDR_MASK,
+ CONFIG_ECC_SRAM_ADDR_SHIFT,
+ ECC_SRAM_ADDR >> 3);
+
+ /* Enable ECC status in SRAM */
+ vf610_nfc_set(nfc, NFC_FLASH_CONFIG, CONFIG_ECC_SRAM_REQ_BIT);
+ }
}
static int vf610_nfc_probe(struct platform_device *pdev)
@@ -610,6 +770,45 @@ static int vf610_nfc_probe(struct platform_device *pdev)
goto error;
}
+ if (chip->ecc.mode == NAND_ECC_HW) {
+ if (mtd->writesize != PAGE_2K && mtd->oobsize < 64) {
+ dev_err(nfc->dev, "Unsupported flash with hwecc\n");
+ err = -ENXIO;
+ goto error;
+ }
+
+ if (chip->ecc.size != mtd->writesize) {
+ dev_err(nfc->dev, "Step size needs to be page size\n");
+ err = -ENXIO;
+ goto error;
+ }
+
+ /* Only 64 byte ECC layouts known */
+ if (mtd->oobsize > 64)
+ mtd->oobsize = 64;
+
+ if (chip->ecc.strength == 32) {
+ nfc->ecc_mode = ECC_60_BYTE;
+ chip->ecc.bytes = 60;
+ chip->ecc.layout = &vf610_nfc_ecc60;
+ } else if (chip->ecc.strength == 24) {
+ nfc->ecc_mode = ECC_45_BYTE;
+ chip->ecc.bytes = 45;
+ chip->ecc.layout = &vf610_nfc_ecc45;
+ } else {
+ dev_err(nfc->dev, "Unsupported ECC strength\n");
+ err = -ENXIO;
+ goto error;
+ }
+
+ /* propagate ecc.layout to mtd_info */
+ mtd->ecclayout = chip->ecc.layout;
+ chip->ecc.read_page = vf610_nfc_read_page;
+ chip->ecc.write_page = vf610_nfc_write_page;
+
+ chip->ecc.size = PAGE_2K;
+ }
+
/* second phase scan */
if (nand_scan_tail(mtd)) {
err = -ENXIO;
--
2.5.1
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/