[PATCH 1/3] mtd: nand: Add on-die ECC support

Richard Weinberger
2015-03-25T14:03:18Z

Some Micron NAND chips offer an on-die ECC (AKA internal ECC)
feature. It is useful when the host-platform does not offer
multi-bit ECC and software ECC is not feasible.

Based on original work by David Mosberger <davidm@egauge.net>

Signed-off-by: Richard Weinberger <richard@nod.at>
---
drivers/mtd/nand/nand_base.c | 66 +++++++++-
drivers/mtd/nand/nand_ondie.c | 266 +++++++++++++++++++++++++++++++++++++++++
include/linux/mtd/nand.h | 6 +
include/linux/mtd/nand_ondie.h | 40 +++++++
4 files changed, 374 insertions(+), 4 deletions(-)
create mode 100644 drivers/mtd/nand/nand_ondie.c
create mode 100644 include/linux/mtd/nand_ondie.h

diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
index df7eb4f..92e7ed7 100644
--- a/drivers/mtd/nand/nand_base.c
+++ b/drivers/mtd/nand/nand_base.c
@@ -43,6 +43,7 @@
#include <linux/mtd/nand.h>
#include <linux/mtd/nand_ecc.h>
#include <linux/mtd/nand_bch.h>
+#include <linux/mtd/nand_ondie.h>
#include <linux/interrupt.h>
#include <linux/bitops.h>
#include <linux/leds.h>
@@ -79,6 +80,20 @@ static struct nand_ecclayout nand_oob_64 = {
.length = 38} }
};

+static struct nand_ecclayout nand_oob_64_on_die = {
+ .eccbytes = 32,
+ .eccpos = {
+ 8, 9, 10, 11, 12, 13, 14, 15,
+ 24, 25, 26, 27, 28, 29, 30, 31,
+ 40, 41, 42, 43, 44, 45, 46, 47,
+ 56, 57, 58, 59, 60, 61, 62, 63},
+ .oobfree = {
+ {.offset = 4, .length = 4},
+ {.offset = 20, .length = 4},
+ {.offset = 36, .length = 4},
+ {.offset = 52, .length = 4} }
+};
+
static struct nand_ecclayout nand_oob_128 = {
.eccbytes = 48,
.eccpos = {
@@ -3115,9 +3130,10 @@ static int nand_setup_read_retry_micron(struct mtd_info *mtd, int retry_mode)
/*
* Configure chip properties from Micron vendor-specific ONFI table
*/
-static void nand_onfi_detect_micron(struct nand_chip *chip,
- struct nand_onfi_params *p)
+static void nand_onfi_detect_micron(struct mtd_info *mtd,
+ struct nand_onfi_params *p)
{
+ struct nand_chip *chip = mtd->priv;
struct nand_onfi_vendor_micron *micron = (void *)p->vendor;

if (le16_to_cpu(p->vendor_revision) < 1)
@@ -3125,6 +3141,8 @@ static void nand_onfi_detect_micron(struct nand_chip *chip,

chip->read_retries = micron->read_retry_options;
chip->setup_read_retry = nand_setup_read_retry_micron;
+
+ nand_onfi_detect_on_die_ecc(mtd);
}

/*
@@ -3226,7 +3244,7 @@ static int nand_flash_detect_onfi(struct mtd_info *mtd, struct nand_chip *chip,
}

if (p->jedec_id == NAND_MFR_MICRON)
- nand_onfi_detect_micron(chip, p);
+ nand_onfi_detect_micron(mtd, p);

return 1;
}
@@ -4056,6 +4074,40 @@ int nand_scan_tail(struct mtd_info *mtd)
}
break;

+ case NAND_ECC_HW_ON_DIE:
+ if (!mtd_nand_has_on_die()) {
+ pr_warn("CONFIG_MTD_NAND_ECC_ON_DIE not enabled\n");
+ BUG();
+ }
+ /*
+ * nand_bbt.c by default puts the BBT marker at
+ * offset 8 in OOB, which is used for ECC (see
+ * nand_oob_64_on_die).
+ * Fixed by not using OOB for BBT marker.
+ */
+ chip->bbt_options |= NAND_BBT_NO_OOB;
+ ecc->layout = &nand_oob_64_on_die;
+ ecc->read_page = nand_read_page_on_die;
+ ecc->read_subpage = nand_read_subpage_on_die;
+ ecc->write_page = nand_write_page_raw;
+ ecc->read_oob = nand_read_oob_std;
+ ecc->read_page_raw = nand_read_page_raw;
+ ecc->write_page_raw = nand_write_page_raw;
+ ecc->write_oob = nand_write_oob_std;
+ ecc->size = 512;
+ ecc->bytes = 8;
+ ecc->strength = 4;
+ ecc->priv = nand_on_die_init(mtd);
+ if (!ecc->priv) {
+ pr_warn("On-Die ECC initialization failed!\n");
+ BUG();
+ }
+ if (nand_setup_on_die_ecc_micron(mtd, 1) != 0) {
+ pr_warn("Unable to enable on-die ECC!\n");
+ BUG();
+ }
+ break;
+
case NAND_ECC_NONE:
pr_warn("NAND_ECC_NONE selected by board driver. This is not recommended!\n");
ecc->read_page = nand_read_page_raw;
@@ -4127,10 +4179,14 @@ int nand_scan_tail(struct mtd_info *mtd)
/* Invalidate the pagebuffer reference */
chip->pagebuf = -1;

- /* Large page NAND with SOFT_ECC should support subpage reads */
+ /*
+ * Large page NAND with SOFT_ECC or on-die ECC should support
+ * subpage reads.
+ */
switch (ecc->mode) {
case NAND_ECC_SOFT:
case NAND_ECC_SOFT_BCH:
+ case NAND_ECC_HW_ON_DIE:
if (chip->page_shift > 9)
chip->options |= NAND_SUBPAGE_READ;
break;
@@ -4232,6 +4288,8 @@ void nand_release(struct mtd_info *mtd)

if (chip->ecc.mode == NAND_ECC_SOFT_BCH)
nand_bch_free((struct nand_bch_control *)chip->ecc.priv);
+ else if (chip->ecc.mode == NAND_ECC_HW_ON_DIE)
+ nand_on_die_destroy(chip->ecc.priv);

mtd_device_unregister(mtd);

diff --git a/drivers/mtd/nand/nand_ondie.c b/drivers/mtd/nand/nand_ondie.c
new file mode 100644
index 0000000..4147ef5
--- /dev/null
+++ b/drivers/mtd/nand/nand_ondie.c
@@ -0,0 +1,266 @@
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/bitops.h>
+#include <linux/mtd/mtd.h>
+#include <linux/mtd/nand.h>
+#include <linux/mtd/nand_ondie.h>
+
+/**
+ * struct nand_on_die_control - private NAND on-die ECC control structure
+ *
+ * As on-die ECC does not report the number of changed bits we have to
+ * count them on our own. If on-die ECC reports flipped bits we re-read the
+ * whole page into @chkbuf and then again with ECC disabled into @rawbuf.
+ * By comparing these buffers the number of changed bits can be identified.
+ *
+ * @chkbuf: Buffer to store a whole page
+ * @rawbuf: Buffer to store a whole page with ECC disabled
+ */
+struct nand_on_die_control {
+ uint8_t *chkbuf;
+ uint8_t *rawbuf;
+};
+
+static int check_for_bitflips(struct mtd_info *mtd, int page)
+{
+ int flips = 0, max_bitflips = 0, i, j, read_size;
+ uint8_t *chkbuf, *rawbuf, *chkoob, *rawoob;
+ struct nand_chip *chip = mtd->priv;
+ struct nand_on_die_control *on_die_ctrl = chip->ecc.priv;
+ uint32_t *eccpos;
+
+ chkbuf = on_die_ctrl->chkbuf;
+ rawbuf = on_die_ctrl->rawbuf;
+ read_size = mtd->writesize + mtd->oobsize;
+
+ /* Read entire page w/OOB area with on-die ECC on */
+ chip->read_buf(mtd, chkbuf, read_size);
+
+ /* Re-read page with on-die ECC off */
+ nand_setup_on_die_ecc_micron(mtd, 0);
+ chip->cmdfunc(mtd, NAND_CMD_READ0, 0x00, page);
+ chip->read_buf(mtd, rawbuf, read_size);
+ nand_setup_on_die_ecc_micron(mtd, 1);
+
+ chkoob = chkbuf + mtd->writesize;
+ rawoob = rawbuf + mtd->writesize;
+ eccpos = chip->ecc.layout->eccpos;
+ for (i = 0; i < chip->ecc.steps; ++i) {
+ /* Count bit flips in the actual data area */
+ flips = 0;
+ for (j = 0; j < chip->ecc.size; ++j)
+ flips += hweight8(chkbuf[j] ^ rawbuf[j]);
+ /* Count bit flips in the ECC bytes */
+ for (j = 0; j < chip->ecc.bytes; ++j) {
+ flips += hweight8(chkoob[*eccpos] ^ rawoob[*eccpos]);
+ ++eccpos;
+ }
+ if (flips > 0)
+ mtd->ecc_stats.corrected += flips;
+ max_bitflips = max_t(int, max_bitflips, flips);
+ chkbuf += chip->ecc.size;
+ rawbuf += chip->ecc.size;
+ }
+
+ /* Re-issue the READ command for the actual data read that follows. */
+ chip->cmdfunc(mtd, NAND_CMD_READ0, 0x00, page);
+
+ return max_bitflips;
+}
+
+static int check_read_status_on_die(struct mtd_info *mtd, int page)
+{
+ struct nand_chip *chip = mtd->priv;
+ int max_bitflips = 0;
+ uint8_t status;
+
+ /* Check ECC status of page just transferred into NAND's page buffer */
+ chip->cmdfunc(mtd, NAND_CMD_STATUS, -1, -1);
+ status = chip->read_byte(mtd);
+
+ /* Switch back to data reading */
+ chip->cmd_ctrl(mtd, NAND_CMD_READ0, NAND_NCE | NAND_CLE | NAND_CTRL_CHANGE);
+ chip->cmd_ctrl(mtd, NAND_CMD_NONE, NAND_NCE | NAND_CTRL_CHANGE);
+
+ if (status & NAND_STATUS_FAIL) {
+ /* Page has invalid ECC */
+ mtd->ecc_stats.failed++;
+ } else if (status & NAND_STATUS_REWRITE) {
+ /*
+ * Micron on-die ECC doesn't report the number of
+ * bitflips, so we have to count them ourself to see
+ * if the error rate is too high. This is
+ * particularly important for pages with stuck bits.
+ */
+ max_bitflips = check_for_bitflips(mtd, page);
+ }
+ return max_bitflips;
+}
+
+
+/**
+ * nand_read_page_on_die - [INTERN] read raw page data without ecc
+ * @mtd: mtd info structure
+ * @chip: nand chip info structure
+ * @buf: buffer to store read data
+ * @oob_required: caller requires OOB data read to chip->oob_poi
+ * @page: page number to read
+ */
+int nand_read_page_on_die(struct mtd_info *mtd, struct nand_chip *chip,
+ uint8_t *buf, int oob_required, int page)
+{
+ uint32_t failed = mtd->ecc_stats.failed;
+ int ret;
+
+ ret = check_read_status_on_die(mtd, page);
+ if (ret < 0 || mtd->ecc_stats.failed != failed)
+ return ret;
+
+ chip->read_buf(mtd, buf, mtd->writesize);
+ if (oob_required)
+ chip->read_buf(mtd, chip->oob_poi, mtd->oobsize);
+ return ret;
+}
+
+/**
+ * nand_read_subpage - [INTERN] on-die-ECC based sub-page read function
+ * @mtd: mtd info structure
+ * @chip: nand chip info structure
+ * @data_offs: offset of requested data within the page
+ * @readlen: data length
+ * @bufpoi: buffer to store read data
+ * @page: page number to read
+ */
+int nand_read_subpage_on_die(struct mtd_info *mtd,
+ struct nand_chip *chip,
+ uint32_t data_offs, uint32_t readlen,
+ uint8_t *bufpoi, int page)
+{
+ int start_step, end_step, num_steps, ret;
+ int data_col_addr;
+ int datafrag_len;
+ uint32_t failed;
+ uint8_t *p;
+
+ /* Column address within the page aligned to ECC size */
+ start_step = data_offs / chip->ecc.size;
+ end_step = (data_offs + readlen - 1) / chip->ecc.size;
+ num_steps = end_step - start_step + 1;
+
+ /* Data size aligned to ECC ecc.size */
+ datafrag_len = num_steps * chip->ecc.size;
+ data_col_addr = start_step * chip->ecc.size;
+ p = bufpoi + data_col_addr;
+
+ failed = mtd->ecc_stats.failed;
+
+ ret = check_read_status_on_die(mtd, page);
+ if (ret < 0 || mtd->ecc_stats.failed != failed) {
+ memset(p, 0, datafrag_len);
+ return ret;
+ }
+
+ /* If we read not a page aligned data */
+ if (data_col_addr != 0)
+ chip->cmdfunc(mtd, NAND_CMD_RNDOUT, data_col_addr, -1);
+
+ chip->read_buf(mtd, p, datafrag_len);
+
+ return ret;
+}
+
+/**
+ * nand_on_die_init - Initialize on-die ECC private data
+ *
+ * @mtd: mtd info structure
+ *
+ * Returns NULL in case of an error.
+ */
+struct nand_on_die_control *nand_on_die_init(struct mtd_info *mtd)
+{
+ struct nand_on_die_control *ctrl = kzalloc(sizeof(*ctrl), GFP_KERNEL);
+
+ if (!ctrl)
+ goto out;
+
+ ctrl->chkbuf = kzalloc(mtd->writesize + mtd->oobsize, GFP_KERNEL);
+ ctrl->rawbuf = kzalloc(mtd->writesize + mtd->oobsize, GFP_KERNEL);
+
+ if (!ctrl->chkbuf || !ctrl->rawbuf) {
+ kfree(ctrl->chkbuf);
+ kfree(ctrl->rawbuf);
+ kfree(ctrl);
+ ctrl = NULL;
+ }
+
+out:
+ return ctrl;
+}
+
+/**
+ * nand_on_die_destroy - Destroy on-die ECC private data
+ *
+ * @ctrl: on-die ECC private data
+ */
+void nand_on_die_destroy(struct nand_on_die_control *ctrl)
+{
+ kfree(ctrl->chkbuf);
+ kfree(ctrl->rawbuf);
+ kfree(ctrl);
+}
+
+static int __nand_setup_on_die_ecc_micron(struct mtd_info *mtd, int enable)
+{
+ struct nand_chip *chip = mtd->priv;
+ uint8_t feature[ONFI_SUBFEATURE_PARAM_LEN] = {0};
+
+ feature[0] = enable ? ONFI_FEATURE_ENABLE_ON_DIE_ECC : 0;
+
+ return chip->onfi_set_features(mtd, chip,
+ ONFI_FEATURE_ADDR_ARRAY_OP_MODE, feature);
+}
+
+/**
+ * nand_setup_on_die_ecc_micron - Enable/Disable on-die ECC mode
+ *
+ * @mtd: mtd info structure
+ * @enable: enables on-die ECC if non-zero
+ */
+int nand_setup_on_die_ecc_micron(struct mtd_info *mtd, int enable)
+{
+ int ret;
+ struct nand_chip *chip = mtd->priv;
+
+ if (chip->ecc.mode != NAND_ECC_HW_ON_DIE)
+ return 0;
+
+ ret = __nand_setup_on_die_ecc_micron(mtd, enable);
+ if (ret)
+ pr_err("Unable to %sable on-die ECC!\n", enable ? "en" : "dis");
+ return ret;
+}
+
+/**
+ * nand_onfi_detect_on_die_ecc - Detect and handle on-die ECC
+ *
+ * @mtd: mtd info structure
+ */
+void nand_onfi_detect_on_die_ecc(struct mtd_info *mtd)
+{
+ u8 features[ONFI_SUBFEATURE_PARAM_LEN];
+ struct nand_chip *chip = mtd->priv;
+
+ if (chip->onfi_get_features(mtd, chip, ONFI_FEATURE_ADDR_ARRAY_OP_MODE,
+ features) < 0)
+ return;
+
+ if (features[0] & ONFI_FEATURE_ENABLE_ON_DIE_ECC &&
+ chip->ecc.mode != NAND_ECC_HW_ON_DIE) {
+
+ pr_info("Requested ECC method is not on-die, disabling on-die ECC\n");
+ __nand_setup_on_die_ecc_micron(mtd, 0);
+ }
+}
+
diff --git a/include/linux/mtd/nand.h b/include/linux/mtd/nand.h
index 3d4ea7e..5216704 100644
--- a/include/linux/mtd/nand.h
+++ b/include/linux/mtd/nand.h
@@ -101,6 +101,7 @@ extern int nand_unlock(struct mtd_info *mtd, loff_t ofs, uint64_t len);
/* Status bits */
#define NAND_STATUS_FAIL 0x01
#define NAND_STATUS_FAIL_N1 0x02
+#define NAND_STATUS_REWRITE 0x08
#define NAND_STATUS_TRUE_READY 0x20
#define NAND_STATUS_READY 0x40
#define NAND_STATUS_WP 0x80
@@ -115,6 +116,7 @@ typedef enum {
NAND_ECC_HW_SYNDROME,
NAND_ECC_HW_OOB_FIRST,
NAND_ECC_SOFT_BCH,
+ NAND_ECC_HW_ON_DIE,
} nand_ecc_modes_t;

/*
@@ -219,6 +221,10 @@ struct nand_chip;
/* Vendor-specific feature address (Micron) */
#define ONFI_FEATURE_ADDR_READ_RETRY 0x89

+/* Vendor-specific array operation mode (Micron) */
+#define ONFI_FEATURE_ADDR_ARRAY_OP_MODE 0x90
+#define ONFI_FEATURE_ENABLE_ON_DIE_ECC 0x08
+
/* ONFI subfeature parameters length */
#define ONFI_SUBFEATURE_PARAM_LEN 4

diff --git a/include/linux/mtd/nand_ondie.h b/include/linux/mtd/nand_ondie.h
new file mode 100644
index 0000000..b2ec2da
--- /dev/null
+++ b/include/linux/mtd/nand_ondie.h
@@ -0,0 +1,40 @@
+#ifndef __MTD_NAND_ONDIE_H__
+#define __MTD_NAND_ONDIE_H__
+
+struct nand_on_die_control;
+
+#if defined(CONFIG_MTD_NAND_ECC_ON_DIE)
+static inline int mtd_nand_has_on_die(void) { return 1; }
+int nand_read_subpage_on_die(struct mtd_info *mtd,
+ struct nand_chip *chip,
+ uint32_t data_offs, uint32_t readlen,
+ uint8_t *bufpoi, int page);
+
+int nand_read_page_on_die(struct mtd_info *mtd, struct nand_chip *chip,
+ uint8_t *buf, int oob_required, int page);
+void nand_onfi_detect_on_die_ecc(struct mtd_info *mtd);
+int nand_setup_on_die_ecc_micron(struct mtd_info *mtd, int enable);
+struct nand_on_die_control *nand_on_die_init(struct mtd_info *mtd);
+void nand_on_die_destroy(struct nand_on_die_control *ctrl);
+#else /* !CONFIG_MTD_NAND_ECC_ON_DIE */
+static inline int mtd_nand_has_on_die(void) { return 0; }
+static inline int nand_read_subpage_on_die(struct mtd_info *mtd,
+ struct nand_chip *chip,
+ uint32_t data_offs,
+ uint32_t readlen,
+ uint8_t *bufpoi, int page)
+{
+ BUG();
+}
+
+static inline int nand_read_page_on_die(struct mtd_info *mtd, struct nand_chip *chip,
+ uint8_t *buf, int oob_required, int page)
+{
+ BUG();
+}
+static inline void nand_onfi_detect_on_die_ecc(struct mtd_info *mtd) { }
+static inline int nand_setup_on_die_ecc_micron(struct mtd_info *mtd, int enable) { return -EINVAL; }
+static inline struct nand_on_die_control *nand_on_die_init(struct mtd_info *mtd) { return NULL; }
+static inline void nand_on_die_destroy(struct nand_on_die_control *ctrl) { }
+#endif /* CONFIG_MTD_NAND_ECC_ON_DIE */
+#endif /* __MTD_NAND_ONDIE_H__ */
--
2.3.4