linux-kernel - [PATCH 1/3] mmc: sd: Add new CONFIG_MMC_PARANOID_SD_INIT for enabling retries during SD detection

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Date:	Tue, 27 Oct 2015 09:55:07 +0100
From:	Bálint Czobor <czoborbalint@...il.com>
To:	unlisted-recipients:; (no To-header on input)
Cc:	linux-kernel@...r.kernel.org, llinux-mmc@...r.kernel.org,
	San Mehat <san@...gle.com>,
	Bálint Czobor <czoborbalint@...il.com>
Subject: [PATCH 1/3] mmc: sd: Add new CONFIG_MMC_PARANOID_SD_INIT for enabling retries during SD detection

From: San Mehat <san@...gle.com>

Signed-off-by: San Mehat <san@...gle.com>
Signed-off-by: Bálint Czobor <czoborbalint@...il.com>
---
 drivers/mmc/core/Kconfig |    8 ++++++++
 drivers/mmc/core/sd.c    |   22 ++++++++++++++++++++++
 2 files changed, 30 insertions(+)

diff --git a/drivers/mmc/core/Kconfig b/drivers/mmc/core/Kconfig
index 9ebee72..1d284c1 100644
--- a/drivers/mmc/core/Kconfig
+++ b/drivers/mmc/core/Kconfig
@@ -11,3 +11,11 @@ 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.
diff --git a/drivers/mmc/core/sd.c b/drivers/mmc/core/sd.c
index 4e7366a..dcbbd33 100644
--- a/drivers/mmc/core/sd.c
+++ b/drivers/mmc/core/sd.c
@@ -797,6 +797,9 @@ int mmc_sd_setup_card(struct mmc_host *host, struct mmc_card *card,
 	bool reinit)
 {
 	int err;
+#ifdef CONFIG_MMC_PARANOID_SD_INIT
+	int retries;
+#endif
 
 	if (!reinit) {
 		/*
@@ -823,7 +826,26 @@ 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;
 	}
-- 
1.7.9.5

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