mmc: core: Allow hosts to specify non-support for SD commands

There are host drivers which needs to valdiate for non-supported SD
commands and returnn error code for such requests.

To improve and simplify the behaviour, let's invent MMC_CAP2_NO_SD
which these host drivers can set to tell the mmc core to skip sending SD
commands during card initialization.
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

drivers/mmc/core/core.c

@@ -2498,15 +2498,18 @@ static int mmc_rescan_try_freq(struct mmc_host *host, unsigned freq)
 
 	mmc_go_idle(host);
 
-	mmc_send_if_cond(host, host->ocr_avail);
+	if (!(host->caps2 & MMC_CAP2_NO_SD))
+		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 (!(host->caps2 & MMC_CAP2_NO_SD))
+		if (!mmc_attach_sd(host))
+			return 0;
+
 	if (!mmc_attach_mmc(host))
 		return 0;
 

include/linux/mmc/host.h

@@ -309,6 +309,7 @@ struct mmc_host {
 #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 */
 #define MMC_CAP2_HS400_ES	(1 << 20)	/* Host supports enhanced strobe */
+#define MMC_CAP2_NO_SD		(1 << 21)	/* Do not send SD commands during initialization */
 
 	mmc_pm_flag_t		pm_caps;	/* supported pm features */