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ARM: MXC: mxcmmc: work around a bug in the SDHC busy line handling 

MX3 SoCs have a silicon bug which corrupts CRC calculation of
multi-block transfers when connected SDIO peripheral doesn't drive the
BUSY line as required by the specs.

One way to prevent this is to only allow 1-bit transfers.

Another way is playing tricks with the DMA engine, but this isn't
mainline yet. So for now, we live with the performance drawback of 1-bit
transfers until a nicer solution is found.

This patch introduces a new host controller callback 'init_card' which
is for now only called from mmc_sdio_init_card().

Signed-off-by: Daniel Mack <daniel@caiaq.de>
Cc: Sascha Hauer <s.hauer@pengutronix.de>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Volker Ernst <volker.ernst@txtr.com>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Michał Mirosław <mirqus@gmail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
This commit is contained in:
Daniel Mack 2010-04-01 10:03:25 +02:00 committed by Sascha Hauer
parent f441b99310
commit 3fcb027d7f
3 changed files with 25 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
drivers/mmc/core/sdio.c
View File

@ -295,6 +295,12 @@ static int mmc_sdio_init_card(struct mmc_host *host, u32 ocr,
card->type = MMC_TYPE_SDIO;
/*
* Call the optional HC's init_card function to handle quirks.
*/
if (host->ops->init_card)
host->ops->init_card(host, card);
/*
* For native busses: set card RCA and quit open drain mode.
*/

16
drivers/mmc/host/mxcmmc.c
View File

@ -724,11 +724,27 @@ static void mxcmci_enable_sdio_irq(struct mmc_host *mmc, int enable)
spin_unlock_irqrestore(&host->lock, flags);
}
static void mxcmci_init_card(struct mmc_host *host, struct mmc_card *card)
{
/*
* MX3 SoCs have a silicon bug which corrupts CRC calculation of
* multi-block transfers when connected SDIO peripheral doesn't
* drive the BUSY line as required by the specs.
* One way to prevent this is to only allow 1-bit transfers.
*/
if (cpu_is_mx3() && card->type == MMC_TYPE_SDIO)
host->caps &= ~MMC_CAP_4_BIT_DATA;
else
host->caps |= MMC_CAP_4_BIT_DATA;
}
static const struct mmc_host_ops mxcmci_ops = {
.request = mxcmci_request,
.set_ios = mxcmci_set_ios,
.get_ro = mxcmci_get_ro,
.enable_sdio_irq = mxcmci_enable_sdio_irq,
.init_card = mxcmci_init_card,
};
static int mxcmci_probe(struct platform_device *pdev)

3
include/linux/mmc/host.h
View File

@ -108,6 +108,9 @@ struct mmc_host_ops {
int (*get_cd)(struct mmc_host *host);
void (*enable_sdio_irq)(struct mmc_host *host, int enable);
/* optional callback for HC quirks */
void (*init_card)(struct mmc_host *host, struct mmc_card *card);
};
struct mmc_card;