mmc: core: Introduce MMC_CAP2_NO_SDIO cap

This patch introduce a new MMC_CAP2_NO_SDIO cap used to tell the mmc
core to not send SDIO specific commands.
Signed-off-by: Carlo Caione <carlo@endlessm.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

drivers/mmc/core/core.c

@@ -2476,15 +2476,20 @@ static int mmc_rescan_try_freq(struct mmc_host *host, unsigned freq)
 	 * sdio_reset sends CMD52 to reset card.  Since we do not know
 	 * if the card is being re-initialized, just send it.  CMD52
 	 * should be ignored by SD/eMMC cards.
+	 * Skip it if we already know that we do not support SDIO commands
 	 */
+	if (!(host->caps2 & MMC_CAP2_NO_SDIO))
 		sdio_reset(host);
+
 	mmc_go_idle(host);
 
 	mmc_send_if_cond(host, host->ocr_avail);
 
 	/* Order's important: probe SDIO, then SD, then MMC */
+	if (!(host->caps2 & MMC_CAP2_NO_SDIO))
 		if (!mmc_attach_sdio(host))
 			return 0;
+
 	if (!mmc_attach_sd(host))
 		return 0;
 	if (!mmc_attach_mmc(host))

include/linux/mmc/host.h

@@ -290,6 +290,7 @@ 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 */
+#define MMC_CAP2_NO_SDIO	(1 << 19)	/* Do not send SDIO commands during initialization */
 
 	mmc_pm_flag_t		pm_caps;	/* supported pm features */