diff options
| author | Daniel Mack <daniel@caiaq.de> | 2010-04-01 10:03:25 +0200 |
|---|---|---|
| committer | Sascha Hauer <s.hauer@pengutronix.de> | 2010-04-14 09:18:07 +0200 |
| commit | 3fcb027d7fd749569665d34a79ce2a8e00bc2ed6 (patch) | |
| tree | 154b65062a5e2c0ff94c9463c8dfe7bfc905affd /drivers/mmc/host | |
| parent | f441b993101d4ee95222ccbaad1e0dd53ea90b64 (diff) | |
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>
Diffstat (limited to 'drivers/mmc/host')
| -rw-r--r-- | drivers/mmc/host/mxcmmc.c | 16 |
1 files changed, 16 insertions, 0 deletions
diff --git a/drivers/mmc/host/mxcmmc.c b/drivers/mmc/host/mxcmmc.c index 51e880c8f19..2c53024ee43 100644 --- a/drivers/mmc/host/mxcmmc.c +++ b/drivers/mmc/host/mxcmmc.c @@ -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) |