[4/6] mmc: sd: Add new CONFIG_MMC_PARANOID_SD_INIT for enabling retries during SD detection

Commit Message

John Stultz April 23, 2011, 1:01 a.m. UTC

From: San Mehat <[e-mail]>

CC: Chris Ball <[e-mail]>
CC: Arnd Bergmann <[e-mail]>
CC: Dima Zavin <[e-mail]>
Signed-off-by: San Mehat <[e-mail]>
[Add depends on EXPERIMENTAL -jstultz]
Signed-off-by: John Stultz <[e-mail]>
---
 drivers/mmc/core/Kconfig |    9 +++++++++
 drivers/mmc/core/sd.c    |   22 ++++++++++++++++++++++
 2 files changed, 31 insertions(+), 0 deletions(-)

Comments

Arnd Bergmann April 26, 2011, 1:35 p.m. UTC | #1

On Saturday 23 April 2011, John Stultz wrote:
> @@ -482,7 +485,26 @@ 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
> +

I see no reason to have this as a compile time option. Having retries in here
might be useful, but a better place would be inside of mmc_read_switch()
or mmc_sd_switch() so it is only done if the error comes from the controller,
not for cases where we know it will fail (e.g. !(card->csd.cmdclass & CCC_SWITCH)).

I would also recommend being a bit less noisy, e.g. print a warning only
after either giving up or succeeding a retry.

	Arnd
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Patch

diff --git a/drivers/mmc/core/Kconfig b/drivers/mmc/core/Kconfig
index ef10387..ffc671e 100644
--- a/drivers/mmc/core/Kconfig
+++ b/drivers/mmc/core/Kconfig
@@ -27,3 +27,12 @@  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)"
+	depends on 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 6dac89f..c0f14cb 100644
--- a/drivers/mmc/core/sd.c
+++ b/drivers/mmc/core/sd.c
@@ -403,6 +403,9 @@  struct device_type sd_type = {
 int mmc_sd_get_cid(struct mmc_host *host, u32 ocr, u32 *cid)
 {
 	int err;
+#ifdef CONFIG_MMC_PARANOID_SD_INIT
+	int retries;
+#endif
 
 	/*
 	 * Since we're changing the OCR value, we seem to
@@ -482,7 +485,26 @@  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;
 	}