mtd: nand: hynix: Add read-retry support for 1x nm MLC NANDs
authorBoris Brezillon <boris.brezillon@free-electrons.com>
Fri, 27 May 2016 08:15:03 +0000 (10:15 +0200)
committerBoris Brezillon <boris.brezillon@free-electrons.com>
Wed, 8 Mar 2017 22:21:24 +0000 (23:21 +0100)
All Hynix MLC NANDs produced with the 1x nm process support read-retry.
This read retry implementation should also be re-usable for other Hynix
NANDs, but the method to retrieve the read-retry parameters from the
read-retry OTP area might change a bit (some NANDs are even using a fixed
set of values instead of retrieving those information from the OTP area).

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Acked-by: Richard Weinberger <richard@nod.at>
drivers/mtd/nand/nand_hynix.c

index 57c4ed894dfb5b2f90c1fdb2b30f0cf3ba7de779..2a5d0efea4984c9487c36675a898b696a1cc61b9 100644 (file)
 
 #include <linux/mtd/nand.h>
 #include <linux/sizes.h>
+#include <linux/slab.h>
+
+#define NAND_HYNIX_CMD_SET_PARAMS      0x36
+#define NAND_HYNIX_CMD_APPLY_PARAMS    0x16
+
+#define NAND_HYNIX_1XNM_RR_REPEAT      8
+
+/**
+ * struct hynix_read_retry - read-retry data
+ * @nregs: number of register to set when applying a new read-retry mode
+ * @regs: register offsets (NAND chip dependent)
+ * @values: array of values to set in registers. The array size is equal to
+ *         (nregs * nmodes)
+ */
+struct hynix_read_retry {
+       int nregs;
+       const u8 *regs;
+       u8 values[0];
+};
+
+/**
+ * struct hynix_nand - private Hynix NAND struct
+ * @nand_technology: manufacturing process expressed in picometer
+ * @read_retry: read-retry information
+ */
+struct hynix_nand {
+       const struct hynix_read_retry *read_retry;
+};
+
+/**
+ * struct hynix_read_retry_otp - structure describing how the read-retry OTP
+ *                              area
+ * @nregs: number of hynix private registers to set before reading the reading
+ *        the OTP area
+ * @regs: registers that should be configured
+ * @values: values that should be set in regs
+ * @page: the address to pass to the READ_PAGE command. Depends on the NAND
+ *       chip
+ * @size: size of the read-retry OTP section
+ */
+struct hynix_read_retry_otp {
+       int nregs;
+       const u8 *regs;
+       const u8 *values;
+       int page;
+       int size;
+};
 
 static bool hynix_nand_has_valid_jedecid(struct nand_chip *chip)
 {
@@ -31,6 +78,288 @@ static bool hynix_nand_has_valid_jedecid(struct nand_chip *chip)
        return !strcmp("JEDEC", jedecid);
 }
 
+static int hynix_nand_setup_read_retry(struct mtd_info *mtd, int retry_mode)
+{
+       struct nand_chip *chip = mtd_to_nand(mtd);
+       struct hynix_nand *hynix = nand_get_manufacturer_data(chip);
+       const u8 *values;
+       int status;
+       int i;
+
+       values = hynix->read_retry->values +
+                (retry_mode * hynix->read_retry->nregs);
+
+       /* Enter 'Set Hynix Parameters' mode */
+       chip->cmdfunc(mtd, NAND_HYNIX_CMD_SET_PARAMS, -1, -1);
+
+       /*
+        * Configure the NAND in the requested read-retry mode.
+        * This is done by setting pre-defined values in internal NAND
+        * registers.
+        *
+        * The set of registers is NAND specific, and the values are either
+        * predefined or extracted from an OTP area on the NAND (values are
+        * probably tweaked at production in this case).
+        */
+       for (i = 0; i < hynix->read_retry->nregs; i++) {
+               int column = hynix->read_retry->regs[i];
+
+               column |= column << 8;
+               chip->cmdfunc(mtd, NAND_CMD_NONE, column, -1);
+               chip->write_byte(mtd, values[i]);
+       }
+
+       /* Apply the new settings. */
+       chip->cmdfunc(mtd, NAND_HYNIX_CMD_APPLY_PARAMS, -1, -1);
+
+       status = chip->waitfunc(mtd, chip);
+       if (status & NAND_STATUS_FAIL)
+               return -EIO;
+
+       return 0;
+}
+
+/**
+ * hynix_get_majority - get the value that is occurring the most in a given
+ *                     set of values
+ * @in: the array of values to test
+ * @repeat: the size of the in array
+ * @out: pointer used to store the output value
+ *
+ * This function implements the 'majority check' logic that is supposed to
+ * overcome the unreliability of MLC NANDs when reading the OTP area storing
+ * the read-retry parameters.
+ *
+ * It's based on a pretty simple assumption: if we repeat the same value
+ * several times and then take the one that is occurring the most, we should
+ * find the correct value.
+ * Let's hope this dummy algorithm prevents us from losing the read-retry
+ * parameters.
+ */
+static int hynix_get_majority(const u8 *in, int repeat, u8 *out)
+{
+       int i, j, half = repeat / 2;
+
+       /*
+        * We only test the first half of the in array because we must ensure
+        * that the value is at least occurring repeat / 2 times.
+        *
+        * This loop is suboptimal since we may count the occurrences of the
+        * same value several time, but we are doing that on small sets, which
+        * makes it acceptable.
+        */
+       for (i = 0; i < half; i++) {
+               int cnt = 0;
+               u8 val = in[i];
+
+               /* Count all values that are matching the one at index i. */
+               for (j = i + 1; j < repeat; j++) {
+                       if (in[j] == val)
+                               cnt++;
+               }
+
+               /* We found a value occurring more than repeat / 2. */
+               if (cnt > half) {
+                       *out = val;
+                       return 0;
+               }
+       }
+
+       return -EIO;
+}
+
+static int hynix_read_rr_otp(struct nand_chip *chip,
+                            const struct hynix_read_retry_otp *info,
+                            void *buf)
+{
+       struct mtd_info *mtd = nand_to_mtd(chip);
+       int i;
+
+       chip->cmdfunc(mtd, NAND_CMD_RESET, -1, -1);
+
+       chip->cmdfunc(mtd, NAND_HYNIX_CMD_SET_PARAMS, -1, -1);
+
+       for (i = 0; i < info->nregs; i++) {
+               int column = info->regs[i];
+
+               column |= column << 8;
+               chip->cmdfunc(mtd, NAND_CMD_NONE, column, -1);
+               chip->write_byte(mtd, info->values[i]);
+       }
+
+       chip->cmdfunc(mtd, NAND_HYNIX_CMD_APPLY_PARAMS, -1, -1);
+
+       /* Sequence to enter OTP mode? */
+       chip->cmdfunc(mtd, 0x17, -1, -1);
+       chip->cmdfunc(mtd, 0x04, -1, -1);
+       chip->cmdfunc(mtd, 0x19, -1, -1);
+
+       /* Now read the page */
+       chip->cmdfunc(mtd, NAND_CMD_READ0, 0x0, info->page);
+       chip->read_buf(mtd, buf, info->size);
+
+       /* Put everything back to normal */
+       chip->cmdfunc(mtd, NAND_CMD_RESET, -1, -1);
+       chip->cmdfunc(mtd, NAND_HYNIX_CMD_SET_PARAMS, 0x38, -1);
+       chip->write_byte(mtd, 0x0);
+       chip->cmdfunc(mtd, NAND_HYNIX_CMD_APPLY_PARAMS, -1, -1);
+       chip->cmdfunc(mtd, NAND_CMD_READ0, 0x0, -1);
+
+       return 0;
+}
+
+#define NAND_HYNIX_1XNM_RR_COUNT_OFFS                          0
+#define NAND_HYNIX_1XNM_RR_REG_COUNT_OFFS                      8
+#define NAND_HYNIX_1XNM_RR_SET_OFFS(x, setsize, inv)           \
+       (16 + ((((x) * 2) + ((inv) ? 1 : 0)) * (setsize)))
+
+static int hynix_mlc_1xnm_rr_value(const u8 *buf, int nmodes, int nregs,
+                                  int mode, int reg, bool inv, u8 *val)
+{
+       u8 tmp[NAND_HYNIX_1XNM_RR_REPEAT];
+       int val_offs = (mode * nregs) + reg;
+       int set_size = nmodes * nregs;
+       int i, ret;
+
+       for (i = 0; i < NAND_HYNIX_1XNM_RR_REPEAT; i++) {
+               int set_offs = NAND_HYNIX_1XNM_RR_SET_OFFS(i, set_size, inv);
+
+               tmp[i] = buf[val_offs + set_offs];
+       }
+
+       ret = hynix_get_majority(tmp, NAND_HYNIX_1XNM_RR_REPEAT, val);
+       if (ret)
+               return ret;
+
+       if (inv)
+               *val = ~*val;
+
+       return 0;
+}
+
+static u8 hynix_1xnm_mlc_read_retry_regs[] = {
+       0xcc, 0xbf, 0xaa, 0xab, 0xcd, 0xad, 0xae, 0xaf
+};
+
+static int hynix_mlc_1xnm_rr_init(struct nand_chip *chip,
+                                 const struct hynix_read_retry_otp *info)
+{
+       struct hynix_nand *hynix = nand_get_manufacturer_data(chip);
+       struct hynix_read_retry *rr = NULL;
+       int ret, i, j;
+       u8 nregs, nmodes;
+       u8 *buf;
+
+       buf = kmalloc(info->size, GFP_KERNEL);
+       if (!buf)
+               return -ENOMEM;
+
+       ret = hynix_read_rr_otp(chip, info, buf);
+       if (ret)
+               goto out;
+
+       ret = hynix_get_majority(buf, NAND_HYNIX_1XNM_RR_REPEAT,
+                                &nmodes);
+       if (ret)
+               goto out;
+
+       ret = hynix_get_majority(buf + NAND_HYNIX_1XNM_RR_REPEAT,
+                                NAND_HYNIX_1XNM_RR_REPEAT,
+                                &nregs);
+       if (ret)
+               goto out;
+
+       rr = kzalloc(sizeof(*rr) + (nregs * nmodes), GFP_KERNEL);
+       if (!rr)
+               goto out;
+
+       for (i = 0; i < nmodes; i++) {
+               for (j = 0; j < nregs; j++) {
+                       u8 *val = rr->values + (i * nregs);
+
+                       ret = hynix_mlc_1xnm_rr_value(buf, nmodes, nregs, i, j,
+                                                     false, val);
+                       if (!ret)
+                               continue;
+
+                       ret = hynix_mlc_1xnm_rr_value(buf, nmodes, nregs, i, j,
+                                                     true, val);
+                       if (ret)
+                               goto out;
+               }
+       }
+
+       rr->nregs = nregs;
+       rr->regs = hynix_1xnm_mlc_read_retry_regs;
+       hynix->read_retry = rr;
+       chip->setup_read_retry = hynix_nand_setup_read_retry;
+       chip->read_retries = nmodes;
+
+out:
+       kfree(buf);
+
+       if (ret)
+               kfree(rr);
+
+       return ret;
+}
+
+static const u8 hynix_mlc_1xnm_rr_otp_regs[] = { 0x38 };
+static const u8 hynix_mlc_1xnm_rr_otp_values[] = { 0x52 };
+
+static const struct hynix_read_retry_otp hynix_mlc_1xnm_rr_otps[] = {
+       {
+               .nregs = ARRAY_SIZE(hynix_mlc_1xnm_rr_otp_regs),
+               .regs = hynix_mlc_1xnm_rr_otp_regs,
+               .values = hynix_mlc_1xnm_rr_otp_values,
+               .page = 0x21f,
+               .size = 784
+       },
+       {
+               .nregs = ARRAY_SIZE(hynix_mlc_1xnm_rr_otp_regs),
+               .regs = hynix_mlc_1xnm_rr_otp_regs,
+               .values = hynix_mlc_1xnm_rr_otp_values,
+               .page = 0x200,
+               .size = 528,
+       },
+};
+
+static int hynix_nand_rr_init(struct nand_chip *chip)
+{
+       int i, ret = 0;
+       bool valid_jedecid;
+
+       valid_jedecid = hynix_nand_has_valid_jedecid(chip);
+
+       /*
+        * We only support read-retry for 1xnm NANDs, and those NANDs all
+        * expose a valid JEDEC ID.
+        */
+       if (valid_jedecid) {
+               u8 nand_tech = chip->id.data[5] >> 4;
+
+               /* 1xnm technology */
+               if (nand_tech == 4) {
+                       for (i = 0; i < ARRAY_SIZE(hynix_mlc_1xnm_rr_otps);
+                            i++) {
+                               /*
+                                * FIXME: Hynix recommend to copy the
+                                * read-retry OTP area into a normal page.
+                                */
+                               ret = hynix_mlc_1xnm_rr_init(chip,
+                                               hynix_mlc_1xnm_rr_otps);
+                               if (!ret)
+                                       break;
+                       }
+               }
+       }
+
+       if (ret)
+               pr_warn("failed to initialize read-retry infrastructure");
+
+       return 0;
+}
+
 static void hynix_nand_extract_oobsize(struct nand_chip *chip,
                                       bool valid_jedecid)
 {
@@ -258,17 +587,43 @@ static void hynix_nand_decode_id(struct nand_chip *chip)
        hynix_nand_extract_scrambling_requirements(chip, valid_jedecid);
 }
 
+static void hynix_nand_cleanup(struct nand_chip *chip)
+{
+       struct hynix_nand *hynix = nand_get_manufacturer_data(chip);
+
+       if (!hynix)
+               return;
+
+       kfree(hynix->read_retry);
+       kfree(hynix);
+       nand_set_manufacturer_data(chip, NULL);
+}
+
 static int hynix_nand_init(struct nand_chip *chip)
 {
+       struct hynix_nand *hynix;
+       int ret;
+
        if (!nand_is_slc(chip))
                chip->bbt_options |= NAND_BBT_SCANLASTPAGE;
        else
                chip->bbt_options |= NAND_BBT_SCAN2NDPAGE;
 
-       return 0;
+       hynix = kzalloc(sizeof(*hynix), GFP_KERNEL);
+       if (!hynix)
+               return -ENOMEM;
+
+       nand_set_manufacturer_data(chip, hynix);
+
+       ret = hynix_nand_rr_init(chip);
+       if (ret)
+               hynix_nand_cleanup(chip);
+
+       return ret;
 }
 
 const struct nand_manufacturer_ops hynix_nand_manuf_ops = {
        .detect = hynix_nand_decode_id,
        .init = hynix_nand_init,
+       .cleanup = hynix_nand_cleanup,
 };