mmc: sdhci-s3c: Fix mmc card I/O problem

This patch fixes the problem in sdhci-s3c host driver for
Samsung Soc's. During the card identification stage the
mmc core driver enumerates for the best bus width in combination
with the highest available data rate. It starts enumerating from
the highest bus width (8) to lowest bus width (1).

In case of few MMC cards the 4-bit bus enumeration fails and tries
the 1-bit bus enumeration. When switched to 1-bit bus mode the host driver
has to clear the previous bus width setting and apply the new setting.

The current patch will clear the previous bus mode and apply the new
mode setting.

Signed-off-by: Girish K S <girish.shivananjappa@linaro.org>
---
 drivers/mmc/host/sdhci-s3c.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

This patch looks fine to me.

Acked-by: Jaehoon Chung <jh80.chung@samsung.com>

Girish K S wrote:

> This patch fixes the problem in sdhci-s3c host driver for
> Samsung Soc's. During the card identification stage the
> mmc core driver enumerates for the best bus width in combination
> with the highest available data rate. It starts enumerating from
> the highest bus width (8) to lowest bus width (1).
> 
> In case of few MMC cards the 4-bit bus enumeration fails and tries
> the 1-bit bus enumeration. When switched to 1-bit bus mode the host driver
> has to clear the previous bus width setting and apply the new setting.
> 
> The current patch will clear the previous bus mode and apply the new
> mode setting.
> 
> Signed-off-by: Girish K S <girish.shivananjappa@linaro.org>
> ---
>  drivers/mmc/host/sdhci-s3c.c |    2 ++
>  1 files changed, 2 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/mmc/host/sdhci-s3c.c b/drivers/mmc/host/sdhci-s3c.c
> index 2bd7bf4..fe886d6 100644
> --- a/drivers/mmc/host/sdhci-s3c.c
> +++ b/drivers/mmc/host/sdhci-s3c.c
> @@ -302,6 +302,8 @@ static int sdhci_s3c_platform_8bit_width(struct sdhci_host *host, int width)
>  		ctrl &= ~SDHCI_CTRL_8BITBUS;
>  		break;
>  	default:
> +		ctrl &= ~SDHCI_CTRL_4BITBUS;
> +		ctrl &= ~SDHCI_CTRL_8BITBUS;
>  		break;
>  	}
>

Hi,

On Fri, Aug 26 2011, Girish K S wrote:
> This patch fixes the problem in sdhci-s3c host driver for
> Samsung Soc's. During the card identification stage the
> mmc core driver enumerates for the best bus width in combination
> with the highest available data rate. It starts enumerating from
> the highest bus width (8) to lowest bus width (1).
>
> In case of few MMC cards the 4-bit bus enumeration fails and tries
> the 1-bit bus enumeration. When switched to 1-bit bus mode the host driver
> has to clear the previous bus width setting and apply the new setting.
>
> The current patch will clear the previous bus mode and apply the new
> mode setting.
>
> Signed-off-by: Girish K S <girish.shivananjappa@linaro.org>

Thanks, pushed to mmc-next for 3.1 with a stable@ tag.

- Chris.