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

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 <>
Signed-off-by: default avatarUlf Hansson <>
parent 0250fdf2
......@@ -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;
ro = host->ops->get_ro(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) {
ro = host->ops->get_ro(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",
......@@ -286,6 +286,7 @@ struct mmc_host {
#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 */
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