linux-kernel - RE: [PATCH v2] mmc:sdio:guarantee setting card data bus width as 4-bit

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Date:	Wed, 6 Jun 2012 18:31:27 -0700
From:	Yong Ding <yongd@...vell.com>
To:	Chris Ball <cjb@...top.org>
CC:	"linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
	Philip Rakity <prakity@...vell.com>,
	"ohad@...ery.com" <ohad@...ery.com>,
	"linus.walleij@...aro.org" <linus.walleij@...aro.org>,
	"ulf.hansson@...ricsson.com" <ulf.hansson@...ricsson.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v2] mmc:sdio:guarantee setting card data bus width as
 4-bit

Chris,
Thanks, and very glad to hear this:-)

Best Wishes,

Yong Ding
Operating Systems Engineering,
Application Processor Systems Engineering

-----Original Message-----
From: Chris Ball [mailto:cjb@...top.org] 
Sent: Wednesday, June 06, 2012 9:24 PM
To: Yong Ding
Cc: linux-mmc@...r.kernel.org; Philip Rakity; ohad@...ery.com; linus.walleij@...aro.org; ulf.hansson@...ricsson.com; linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] mmc:sdio:guarantee setting card data bus width as 4-bit

Hi,

On Tue, May 15 2012, yongd wrote:
>   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  |    7 +++++++
>  include/linux/mmc/sdio.h |    2 ++
>  2 files changed, 9 insertions(+)
>
> diff --git a/drivers/mmc/core/sdio.c b/drivers/mmc/core/sdio.c
> index 13d0e95..7b528cf 100644
> --- a/drivers/mmc/core/sdio.c
> +++ b/drivers/mmc/core/sdio.c
> @@ -218,6 +218,13 @@ 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"%s: SDIO_CCCR_IF is invalid: 0x%02X\n",
> +					mmc_hostname(card->host), 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 */

Thanks, pushed to mmc-next for 3.5.

- Chris.
-- 
Chris Ball   <cjb@...top.org>   <http://printf.net/>
One Laptop Per Child
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