linux-kernel - [PATCH] mmc:sdio:guarantee setting card data bus width as 4-bit

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Message-Id: <1336984510-9723-1-git-send-email-yongd@marvell.com>
Date:	Mon, 14 May 2012 16:35:10 +0800
From:	yongd <yongd@...vell.com>
To:	cjb@...top.org, linux-mmc@...r.kernel.org
Cc:	prakity@...vell.com, ohad@...ery.com, linus.walleij@...aro.org,
	ulf.hansson@...ricsson.com, linux-kernel@...r.kernel.org,
	yongd <yongd@...vell.com>
Subject: [PATCH] mmc:sdio:guarantee setting card data bus width as 4-bit

  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@...vell.com>
---
 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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