From 3fcb027d7fd749569665d34a79ce2a8e00bc2ed6 Mon Sep 17 00:00:00 2001 From: Daniel Mack Date: Thu, 1 Apr 2010 10:03:25 +0200 Subject: ARM: MXC: mxcmmc: work around a bug in the SDHC busy line handling MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Cc: Sascha Hauer Cc: Dan Williams Cc: Volker Ernst Cc: Jiri Kosina Cc: Michał Mirosław Signed-off-by: Sascha Hauer --- drivers/mmc/host/mxcmmc.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) (limited to 'drivers/mmc/host/mxcmmc.c') diff --git a/drivers/mmc/host/mxcmmc.c b/drivers/mmc/host/mxcmmc.c index 51e880c..2c53024 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) -- cgit v1.1