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ar71xx: allow to specify max read size for m25p80

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Reading from the flash chip on the TL-WR2543ND seems buggy.
If the SPI flash driver tries to read too much data in one
SPI transfer, the flash chip returns bogus values. This can
be caused by a buggy flash chip on my board, or it can
be a bug in our SPI driver.

Add a workaround to the m25p80 driver until I find out the
root cause of the problem. The patch allows to specify the
maximum numner of bytes which can be read safely withint
one SPI transfer.

SVN-Revision: 29679
This commit is contained in:
Gabor Juhos 2012-01-07 19:36:33 +00:00
parent 8b567fb508
commit a56bdeff9d
1 changed files with 112 additions and 0 deletions
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112
target/linux/ar71xx/patches-2.6.39/113-mtd-m25p80-allow-to-specify-max-read-size.patch Normal file
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@ -0,0 +1,112 @@
--- a/drivers/mtd/devices/m25p80.c
+++ b/drivers/mtd/devices/m25p80.c
@@ -94,6 +94,7 @@ struct m25p {
u16 addr_width;
u8 erase_opcode;
u8 *command;
+ size_t max_read_len;
};
static inline struct m25p *mtd_to_m25p(struct mtd_info *mtd)
@@ -341,6 +342,7 @@ static int m25p80_read(struct mtd_info *
struct m25p *flash = mtd_to_m25p(mtd);
struct spi_transfer t[2];
struct spi_message m;
+ loff_t ofs;
DEBUG(MTD_DEBUG_LEVEL2, "%s: %s %s 0x%08x, len %zd\n",
dev_name(&flash->spi->dev), __func__, "from",
@@ -364,8 +366,6 @@ static int m25p80_read(struct mtd_info *
t[0].len = m25p_cmdsz(flash) + FAST_READ_DUMMY_BYTE;
spi_message_add_tail(&t[0], &m);
- t[1].rx_buf = buf;
- t[1].len = len;
spi_message_add_tail(&t[1], &m);
/* Byte count starts at zero. */
@@ -373,13 +373,6 @@ static int m25p80_read(struct mtd_info *
mutex_lock(&flash->lock);
- /* Wait till previous write/erase is done. */
- if (wait_till_ready(flash)) {
- /* REVISIT status return?? */
- mutex_unlock(&flash->lock);
- return 1;
- }
-
/* FIXME switch to OPCODE_FAST_READ. It's required for higher
* clocks; and at this writing, every chip this driver handles
* supports that opcode.
@@ -387,11 +380,44 @@ static int m25p80_read(struct mtd_info *
/* Set up the write data buffer. */
flash->command[0] = OPCODE_READ;
- m25p_addr2cmd(flash, from, flash->command);
- spi_sync(flash->spi, &m);
+ ofs = 0;
+ while (len) {
+ size_t readlen;
+ size_t done;
+ int ret;
+
+ ret = wait_till_ready(flash);
+ if (ret) {
+ mutex_unlock(&flash->lock);
+ return 1;
+ }
+
+ if (flash->max_read_len > 0 &&
+ flash->max_read_len < len)
+ readlen = flash->max_read_len;
+ else
+ readlen = len;
+
+ t[1].rx_buf = buf + ofs;
+ t[1].len = readlen;
+
+ m25p_addr2cmd(flash, from + ofs, flash->command);
+
+ spi_sync(flash->spi, &m);
- *retlen = m.actual_length - m25p_cmdsz(flash) - FAST_READ_DUMMY_BYTE;
+ done = m.actual_length - m25p_cmdsz(flash) -
+ FAST_READ_DUMMY_BYTE;
+ if (done != readlen) {
+ mutex_unlock(&flash->lock);
+ return 1;
+ }
+
+ ofs += done;
+ len -= done;
+ }
+
+ *retlen = ofs;
mutex_unlock(&flash->lock);
@@ -901,6 +927,12 @@ static int __devinit m25p_probe(struct s
flash->mtd.erase = m25p80_erase;
flash->mtd.read = m25p80_read;
+ if (data && data->max_read_len) {
+ flash->max_read_len = data->max_read_len;
+ dev_warn(&spi->dev, "max_read_len set to %d bytes\n",
+ flash->max_read_len);
+ }
+
/* sst flash chips use AAI word program */
if (info->jedec_id >> 16 == 0xbf)
flash->mtd.write = sst_write;
--- a/include/linux/spi/flash.h
+++ b/include/linux/spi/flash.h
@@ -26,6 +26,7 @@ struct flash_platform_data {
char *type;
const char **part_probes;
+ size_t max_read_len;
/* we'll likely add more ... use JEDEC IDs, etc */
};