linux-kernel - Re: MMC: Add 8-bit bus width support

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Message-ID: <20081117124945.GF9161@fluff.org.uk>
Date:	Mon, 17 Nov 2008 12:49:45 +0000
From:	Ben Dooks <ben-linux@...ff.org>
To:	Jarkko Lavinen <jarkko.lavinen@...ia.com>
Cc:	Pierre Ossman <drzeus@...eus.cx>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: MMC: Add 8-bit bus width support

On Mon, Nov 17, 2008 at 02:35:21PM +0200, Jarkko Lavinen wrote:
> Hi Pierre
> 
> Here is a patch which adds 8-bit bus width suport to the mmc
> driver common part.  
> 
> I've tested it with a test board with 8-bit eMMC device on Omap
> 3420 HSMMC controller. It speeds up DMA transfer from host to the
> card and most of the time is spent in busy polling for the card
> to become ready.

I'll try and give this a test on the S3C6410, which has the option
of having channel 1 being 8bit. Any idea of cards that support 8bit?
 
> Regards
> Jarkko Lavinen
> 
> >From d038f6ebe177f3f4ae2ae1f8a9dfc648e5625909 Mon Sep 17 00:00:00 2001
> From: Jarkko Lavinen <jarkko.lavinen@...ia.com>
> Date: Mon, 17 Nov 2008 14:30:17 +0200
> Subject: [PATCH] MMC: Add 8-bit bus width support
> 
> Signed-off-by: Jarkko Lavinen <jarkko.lavinen@...ia.com>
> ---
>  drivers/mmc/core/mmc.c   |   18 ++++++++++++++----
>  include/linux/mmc/host.h |    2 ++
>  2 files changed, 16 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
> index fdd7c76..c232d11 100644
> --- a/drivers/mmc/core/mmc.c
> +++ b/drivers/mmc/core/mmc.c
> @@ -434,13 +434,24 @@ static int mmc_init_card(struct mmc_host *host, u32 ocr,
>  	 * Activate wide bus (if supported).
>  	 */
>  	if ((card->csd.mmca_vsn >= CSD_SPEC_VER_4) &&
> -		(host->caps & MMC_CAP_4_BIT_DATA)) {
> +	    (host->caps & (MMC_CAP_4_BIT_DATA | MMC_CAP_8_BIT_DATA))) {
> +		unsigned ext_csd_bit, bus_width;
> +
> +		if (host->caps & MMC_CAP_8_BIT_DATA) {
> +			ext_csd_bit = EXT_CSD_BUS_WIDTH_8;
> +			bus_width = MMC_BUS_WIDTH_8;
> +		} else {
> +			ext_csd_bit = EXT_CSD_BUS_WIDTH_4;
> +			bus_width = MMC_BUS_WIDTH_4;
> +		}
> +
>  		err = mmc_switch(card, EXT_CSD_CMD_SET_NORMAL,
> -			EXT_CSD_BUS_WIDTH, EXT_CSD_BUS_WIDTH_4);
> +				 EXT_CSD_BUS_WIDTH, ext_csd_bit);
> +
>  		if (err)
>  			goto free_card;
>  
> -		mmc_set_bus_width(card->host, MMC_BUS_WIDTH_4);
> +		mmc_set_bus_width(card->host, bus_width);
>  	}
>  
>  	if (!oldcard)
> @@ -624,4 +635,3 @@ err:
>  
>  	return err;
>  }
> -
> diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
> index f842f23..4e45725 100644
> --- a/include/linux/mmc/host.h
> +++ b/include/linux/mmc/host.h
> @@ -41,6 +41,7 @@ struct mmc_ios {
>  
>  #define MMC_BUS_WIDTH_1		0
>  #define MMC_BUS_WIDTH_4		2
> +#define MMC_BUS_WIDTH_8		3
>  
>  	unsigned char	timing;			/* timing specification used */
>  
> @@ -116,6 +117,7 @@ struct mmc_host {
>  #define MMC_CAP_SDIO_IRQ	(1 << 3)	/* Can signal pending SDIO IRQs */
>  #define MMC_CAP_SPI		(1 << 4)	/* Talks only SPI protocols */
>  #define MMC_CAP_NEEDS_POLL	(1 << 5)	/* Needs polling for card-detection */
> +#define MMC_CAP_8_BIT_DATA	(1 << 6)	/* Can the host do 8 bit transfers */
>  
>  	/* host specific block data */
>  	unsigned int		max_seg_size;	/* see blk_queue_max_segment_size */
> -- 
> 1.5.6.5
> 
> --
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-- 
Ben (ben@...ff.org, http://www.fluff.org/)

  'a smiley only costs 4 bytes'
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