[PATCH 1/2] mmc: add additional quirk for APP_CMD retry

[Joel Johnson]

It was observed (on ClearFog Base) that sending MMC APP_CMD returned
an error on the first attempt. The issue appears to be timing related
since even inserting a puts() short debug entry before the execution
added sufficient delay to receive success on first attempt.

Follow the existing quirks pattern to retry if initial issuance
failed so as to not introduce any delay unless needed.

Signed-off-by: Joel Johnson <mrjoel at lixil.net>
---

 drivers/mmc/mmc.c | 17 ++++++++++++++++-
 include/mmc.h     |  1 +
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/drivers/mmc/mmc.c b/drivers/mmc/mmc.c
index f683b52ead..d43983d4a6 100644
--- a/drivers/mmc/mmc.c
+++ b/drivers/mmc/mmc.c
@@ -1444,6 +1444,20 @@ static int sd_read_ssr(struct mmc *mmc)
 	cmd.cmdarg = mmc->rca << 16;
 
 	err = mmc_send_cmd(mmc, &cmd, NULL);
+#ifdef CONFIG_MMC_QUIRKS
+	if (err && (mmc->quirks & MMC_QUIRK_RETRY_APP_CMD)) {
+		int retries = 4;
+		/*
+		 * It has been seen that APP_CMD may fail on the first
+		 * attempt, let's try a few more times
+		 */
+		do {
+			err = mmc_send_cmd(mmc, &cmd, NULL);
+			if (!err)
+				break;
+		} while (retries--);
+	}
+#endif
 	if (err)
 		return err;
 
@@ -2755,7 +2769,8 @@ int mmc_get_op_cond(struct mmc *mmc)
 
 #ifdef CONFIG_MMC_QUIRKS
 	mmc->quirks = MMC_QUIRK_RETRY_SET_BLOCKLEN |
-		      MMC_QUIRK_RETRY_SEND_CID;
+		      MMC_QUIRK_RETRY_SEND_CID |
+		      MMC_QUIRK_RETRY_APP_CMD;
 #endif
 
 	err = mmc_power_cycle(mmc);
diff --git a/include/mmc.h b/include/mmc.h
index 1a9efe4c38..b5cb514f57 100644
--- a/include/mmc.h
+++ b/include/mmc.h
@@ -331,6 +331,7 @@ static inline bool mmc_is_tuning_cmd(uint cmdidx)
 
 #define MMC_QUIRK_RETRY_SEND_CID	BIT(0)
 #define MMC_QUIRK_RETRY_SET_BLOCKLEN	BIT(1)
+#define MMC_QUIRK_RETRY_APP_CMD	BIT(2)
 
 enum mmc_voltage {
 	MMC_SIGNAL_VOLTAGE_000 = 0,
-- 
2.20.1