yongd at marvell
May 14, 2012, 1:35 AM
Views: 33
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[PATCH] mmc:sdio:guarantee setting card data bus width as 4-bit
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SDIO_CCCR_IF[1:0] in SDIO card is used for card data bus width
setting as below,
00b: 1-bit bus
01b: Reserved
10b: 4-bit bus
11b: 8-bit bus(only for embedded SDIO)
And sdio_enable_wide is for setting data bus width as 4-bit. But
currently, it 1stly read the register, 2ndly OR' 1b with SDIO_CCCR_IF[1],
and then write it back.
As we can see, such way is based on such assumption that the
SDIO_CCCR_IF[0] is always 0. Apparently, this is not right.
Signed-off-by: yongd <yongd [at] marvell>
---
drivers/mmc/core/sdio.c | 6 ++++++
include/linux/mmc/sdio.h | 2 ++
2 files changed, 8 insertions(+)
diff --git a/drivers/mmc/core/sdio.c b/drivers/mmc/core/sdio.c
index 13d0e95..6b6f902 100644
--- a/drivers/mmc/core/sdio.c
+++ b/drivers/mmc/core/sdio.c
@@ -218,6 +218,12 @@ static int sdio_enable_wide(struct mmc_card *card)
if (ret)
return ret;
+ if ((ctrl & SDIO_BUS_WIDTH_MASK)
+ == SDIO_BUS_WIDTH_RESERVED)
+ printk(KERN_WARNING"SDIO_CCCR_IF is invalid: %d\n", ctrl);
+
+ /* set as 4-bit bus width */
+ ctrl &= ~SDIO_BUS_WIDTH_MASK;
ctrl |= SDIO_BUS_WIDTH_4BIT;
ret = mmc_io_rw_direct(card, 1, 0, SDIO_CCCR_IF, ctrl, NULL);
diff --git a/include/linux/mmc/sdio.h b/include/linux/mmc/sdio.h
index c9fe66c..17446d3 100644
--- a/include/linux/mmc/sdio.h
+++ b/include/linux/mmc/sdio.h
@@ -98,7 +98,9 @@
#define SDIO_CCCR_IF 0x07 /* bus interface controls */
+#define SDIO_BUS_WIDTH_MASK 0x03 /* data bus width setting */
#define SDIO_BUS_WIDTH_1BIT 0x00
+#define SDIO_BUS_WIDTH_RESERVED 0x01
#define SDIO_BUS_WIDTH_4BIT 0x02
#define SDIO_BUS_ECSI 0x20 /* Enable continuous SPI interrupt */
#define SDIO_BUS_SCSI 0x40 /* Support continuous SPI interrupt */
--
1.7.9.5
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[PATCH] mmc:sdio:guarantee setting card data bus width as 4-bit
