Commit 3fcb027d authored by Daniel Mack's avatar Daniel Mack Committed by Sascha Hauer
Browse files

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: default avatarDaniel 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: default avatarSascha Hauer <s.hauer@pengutronix.de>
parent f441b993

drivers/mmc/core/sdio.c

+6 −0
Original line number Diff line number Diff line
@@ -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.

	 */

drivers/mmc/host/mxcmmc.c

+16 −0
Original line number Diff line number Diff line
@@ -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)

include/linux/mmc/host.h

+3 −0
Original line number Diff line number Diff line
@@ -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;

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