mtd: nand: don't use {read,write}_buf for 8-bit transfers
According to the Open NAND Flash Interface Specification (ONFI) Revision
3.1 "Parameters are always transferred on the lower 8-bits of the data
bus." for the Get Features and Set Features commands.
So using read_buf and write_buf is wrong for 16-bit wide nand chips as
they use I/O[15:0]. The Get Features command is easily fixed using 4
times the read_byte callback. For Set Features implement a new
overwritable callback "write_byte". Still I expect the default to work
just fine for all controllers and making it overwriteable was just done
for symmetry.
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
[Brian: fixed warning]
Tested-by: Brian Norris <computersforpeace@gmail.com>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>
diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
index b8c74cd..d388c7f 100644
--- a/drivers/mtd/nand/nand_base.c
+++ b/drivers/mtd/nand/nand_base.c
@@ -204,6 +204,51 @@
}
/**
+ * nand_write_byte - [DEFAULT] write single byte to chip
+ * @mtd: MTD device structure
+ * @byte: value to write
+ *
+ * Default function to write a byte to I/O[7:0]
+ */
+static void nand_write_byte(struct mtd_info *mtd, uint8_t byte)
+{
+ struct nand_chip *chip = mtd->priv;
+
+ chip->write_buf(mtd, &byte, 1);
+}
+
+/**
+ * nand_write_byte16 - [DEFAULT] write single byte to a chip with width 16
+ * @mtd: MTD device structure
+ * @byte: value to write
+ *
+ * Default function to write a byte to I/O[7:0] on a 16-bit wide chip.
+ */
+static void nand_write_byte16(struct mtd_info *mtd, uint8_t byte)
+{
+ struct nand_chip *chip = mtd->priv;
+ uint16_t word = byte;
+
+ /*
+ * It's not entirely clear what should happen to I/O[15:8] when writing
+ * a byte. The ONFi spec (Revision 3.1; 2012-09-19, Section 2.16) reads:
+ *
+ * When the host supports a 16-bit bus width, only data is
+ * transferred at the 16-bit width. All address and command line
+ * transfers shall use only the lower 8-bits of the data bus. During
+ * command transfers, the host may place any value on the upper
+ * 8-bits of the data bus. During address transfers, the host shall
+ * set the upper 8-bits of the data bus to 00h.
+ *
+ * One user of the write_byte callback is nand_onfi_set_features. The
+ * four parameters are specified to be written to I/O[7:0], but this is
+ * neither an address nor a command transfer. Let's assume a 0 on the
+ * upper I/O lines is OK.
+ */
+ chip->write_buf(mtd, (uint8_t *)&word, 2);
+}
+
+/**
* nand_write_buf - [DEFAULT] write buffer to chip
* @mtd: MTD device structure
* @buf: data buffer
@@ -2769,6 +2814,7 @@
int addr, uint8_t *subfeature_param)
{
int status;
+ int i;
if (!chip->onfi_version ||
!(le16_to_cpu(chip->onfi_params.opt_cmd)
@@ -2776,7 +2822,9 @@
return -EINVAL;
chip->cmdfunc(mtd, NAND_CMD_SET_FEATURES, addr, -1);
- chip->write_buf(mtd, subfeature_param, ONFI_SUBFEATURE_PARAM_LEN);
+ for (i = 0; i < ONFI_SUBFEATURE_PARAM_LEN; ++i)
+ chip->write_byte(mtd, subfeature_param[i]);
+
status = chip->waitfunc(mtd, chip);
if (status & NAND_STATUS_FAIL)
return -EIO;
@@ -2793,6 +2841,8 @@
static int nand_onfi_get_features(struct mtd_info *mtd, struct nand_chip *chip,
int addr, uint8_t *subfeature_param)
{
+ int i;
+
if (!chip->onfi_version ||
!(le16_to_cpu(chip->onfi_params.opt_cmd)
& ONFI_OPT_CMD_SET_GET_FEATURES))
@@ -2802,7 +2852,8 @@
memset(subfeature_param, 0, ONFI_SUBFEATURE_PARAM_LEN);
chip->cmdfunc(mtd, NAND_CMD_GET_FEATURES, addr, -1);
- chip->read_buf(mtd, subfeature_param, ONFI_SUBFEATURE_PARAM_LEN);
+ for (i = 0; i < ONFI_SUBFEATURE_PARAM_LEN; ++i)
+ *subfeature_param++ = chip->read_byte(mtd);
return 0;
}
@@ -2865,6 +2916,8 @@
chip->block_markbad = nand_default_block_markbad;
if (!chip->write_buf || chip->write_buf == nand_write_buf)
chip->write_buf = busw ? nand_write_buf16 : nand_write_buf;
+ if (!chip->write_byte || chip->write_byte == nand_write_byte)
+ chip->write_byte = busw ? nand_write_byte16 : nand_write_byte;
if (!chip->read_buf || chip->read_buf == nand_read_buf)
chip->read_buf = busw ? nand_read_buf16 : nand_read_buf;
if (!chip->scan_bbt)