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Commit 9f6e0bff authored by Lars-Peter Clausen's avatar Lars-Peter Clausen Committed by Ulf Hansson
Browse files

mmc: Add support for disabling write-protect detection 



It is not uncommon to see systems where there is no physical write-protect
signal (e.g. when using eMMC or microSD card slots). For some controllers,
which have a dedicated write-protection detection logic (like SDHCI
controllers), the get_ro() callback can return bogus data in such a case.

Instead of handling this on a per controller basis this patch adds a new
capability flag to the MMC core that can be set to specify that the result
of get_ro() is invalid. When the flag is set the core will not call
get_ro() and assume that the card is always read-write.

Signed-off-by: default avatarLars-Peter Clausen <lars@metafoo.de>
Signed-off-by: default avatarUlf Hansson <ulf.hansson@linaro.org>
parent 0250fdf2

drivers/mmc/core/sd.c

+23 −7
Original line number Diff line number Diff line
@@ -804,6 +804,28 @@ int mmc_sd_get_csd(struct mmc_host *host, struct mmc_card *card) 
	return 0;

}



static int mmc_sd_get_ro(struct mmc_host *host)

{

	int ro;



	/*

	 * Some systems don't feature a write-protect pin and don't need one.

	 * E.g. because they only have micro-SD card slot. For those systems

	 * assume that the SD card is always read-write.

	 */

	if (host->caps2 & MMC_CAP2_NO_WRITE_PROTECT)

		return 0;



	if (!host->ops->get_ro)

		return -1;



	mmc_host_clk_hold(host);

	ro = host->ops->get_ro(host);

	mmc_host_clk_release(host);



	return ro;

}



int mmc_sd_setup_card(struct mmc_host *host, struct mmc_card *card,

	bool reinit)

{
@@ -855,13 +877,7 @@ int mmc_sd_setup_card(struct mmc_host *host, struct mmc_card *card, 
	 * Check if read-only switch is active.

	 */

	if (!reinit) {

		int ro = -1;



		if (host->ops->get_ro) {

			mmc_host_clk_hold(card->host);

			ro = host->ops->get_ro(host);

			mmc_host_clk_release(card->host);

		}

		int ro = mmc_sd_get_ro(host);



		if (ro < 0) {

			pr_warn("%s: host does not support reading read-only switch, assuming write-enable\n",

include/linux/mmc/host.h

+1 −0
Original line number Diff line number Diff line
@@ -286,6 +286,7 @@ struct mmc_host { 
				 MMC_CAP2_HS400_1_2V)

#define MMC_CAP2_HSX00_1_2V	(MMC_CAP2_HS200_1_2V_SDR | MMC_CAP2_HS400_1_2V)

#define MMC_CAP2_SDIO_IRQ_NOTHREAD (1 << 17)

#define MMC_CAP2_NO_WRITE_PROTECT (1 << 18)	/* No physical write protect pin, assume that card is always read-write */



	mmc_pm_flag_t		pm_caps;	/* supported pm features */