mmc: sdhci: use WP GPIO in sdhci_check_ro()

Even though SDHCI controllers may have a dedicated WP pin that can be
queried using the SDHCI_PRESENT_STATE register, some platforms may
chose to use a separate regular GPIO to route the WP signal. Such a
GPIO is typically represented using the wp-gpios property in the
Device Tree.

Unfortunately, the current sdhci_check_ro() function does not make use
of such GPIO when available: it either uses a host controller specific
->get_ro() operation, or uses the SDHCI_PRESENT_STATE. Several host
controller specific ->get_ro() functions are implemented just to check
a WP GPIO state.

Instead of pushing this to more controller-specific implementations,
let's handle this in the core SDHCI code, just like it is already done
for the CD GPIO in sdhci_get_cd().

The below patch simply changes sdhci_check_ro() to use the value of
the WP GPIO if available.
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

drivers/mmc/host/sdhci.c

@@ -2053,6 +2053,8 @@ static int sdhci_check_ro(struct sdhci_host *host)
 		is_readonly = 0;
 	else if (host->ops->get_ro)
 		is_readonly = host->ops->get_ro(host);
+	else if (mmc_can_gpio_ro(host->mmc))
+		is_readonly = mmc_gpio_get_ro(host->mmc);
 	else
 		is_readonly = !(sdhci_readl(host, SDHCI_PRESENT_STATE)
 				& SDHCI_WRITE_PROTECT);