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SubjectRe: 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@nokia.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@nokia.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@fluff.org, http://www.fluff.org/)

'a smiley only costs 4 bytes'


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