mmc: sd: Add new CONFIG_MMC_PARANOID_SD_INIT for enabling retries during SD detection

Signed-off-by: San Mehat <san@google.com>

drivers/mmc/core/Kconfig

@@ -27,3 +27,11 @@ config MMC_CLKGATE
 	  support handling this in order for it to be of any use.
 
 	  If unsure, say N.
+
+config MMC_PARANOID_SD_INIT
+	bool "Enable paranoid SD card initialization (EXPERIMENTAL)"
+	help
+	  If you say Y here, the MMC layer will be extra paranoid
+	  about re-trying SD init requests. This can be a useful
+	  work-around for buggy controllers and hardware. Enable
+	  if you are experiencing issues with SD detection.

drivers/mmc/core/sd.c

@@ -684,6 +684,9 @@ struct device_type sd_type = {
 int mmc_sd_get_cid(struct mmc_host *host, u32 ocr, u32 *cid, u32 *rocr)
 {
 	int err;
+#ifdef CONFIG_MMC_PARANOID_SD_INIT
+	int retries;
+#endif
 
 	/*
 	 * Since we're changing the OCR value, we seem to
@@ -790,7 +793,26 @@ int mmc_sd_setup_card(struct mmc_host *host, struct mmc_card *card,
 		/*
 		 * Fetch switch information from card.
 		 */
+#ifdef CONFIG_MMC_PARANOID_SD_INIT
+		for (retries = 1; retries <= 3; retries++) {
+			err = mmc_read_switch(card);
+			if (!err) {
+				if (retries > 1) {
+					printk(KERN_WARNING
+					       "%s: recovered\n", 
+					       mmc_hostname(host));
+				}
+				break;
+			} else {
+				printk(KERN_WARNING
+				       "%s: read switch failed (attempt %d)\n",
+				       mmc_hostname(host), retries);
+			}
+		}
+#else
 		err = mmc_read_switch(card);
+#endif
+
 		if (err)
 			return err;
 	}