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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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