[PATCH 1/2] mmc: sdhci_am654: Add retry tuning

[Judith Mendez <jm@ti.com>]

Add retry tuning up to 10 times if we fail to find
a failing region or no passing itapdly. This is
necessary since some eMMC's have been observed to never
find a failing itapdly on the first couple of tuning
iterations, but eventually do. It been observed that the
tuning algorithm does not need to loop more than 10 times
before finding a failing itapdly.

Signed-off-by: Judith Mendez <jm@ti.com>
---
 drivers/mmc/host/sdhci_am654.c | 30 +++++++++++++++++++++++-------
 1 file changed, 23 insertions(+), 7 deletions(-)

diff --git a/drivers/mmc/host/sdhci_am654.c b/drivers/mmc/host/sdhci_am654.c
index 64e10f7c9faa3..c3d485bd4d553 100644
--- a/drivers/mmc/host/sdhci_am654.c
+++ b/drivers/mmc/host/sdhci_am654.c
@@ -86,6 +86,7 @@
 
 #define CLOCK_TOO_SLOW_HZ	50000000
 #define SDHCI_AM654_AUTOSUSPEND_DELAY	-1
+#define RETRY_TUNING_MAX	10
 
 /* Command Queue Host Controller Interface Base address */
 #define SDHCI_AM654_CQE_BASE_ADDR 0x200
@@ -151,6 +152,7 @@ struct sdhci_am654_data {
 	u32 flags;
 	u32 quirks;
 	bool dll_enable;
+	u32 tuning_loop;
 
 #define SDHCI_AM654_QUIRK_FORCE_CDTEST BIT(0)
 };
@@ -453,12 +455,14 @@ static u32 sdhci_am654_calculate_itap(struct sdhci_host *host, struct window
 	int prev_fail_end = -1;
 	u8 i;
 
-	if (!num_fails)
-		return ITAPDLY_LAST_INDEX >> 1;
+	if (!num_fails) {
+		/* Retry tuning */
+		return -1;
+	}
 
 	if (fail_window->length == ITAPDLY_LENGTH) {
-		dev_err(dev, "No passing ITAPDLY, return 0\n");
-		return 0;
+		/* Retry tuning */
+		return -1;
 	}
 
 	first_fail_start = fail_window->start;
@@ -504,6 +508,7 @@ static int sdhci_am654_platform_execute_tuning(struct sdhci_host *host,
 	u8 curr_pass, itap;
 	u8 fail_index = 0;
 	u8 prev_pass = 1;
+	int ret;
 
 	memset(fail_window, 0, sizeof(fail_window));
 
@@ -532,10 +537,20 @@ static int sdhci_am654_platform_execute_tuning(struct sdhci_host *host,
 	if (fail_window[fail_index].length != 0)
 		fail_index++;
 
-	itap = sdhci_am654_calculate_itap(host, fail_window, fail_index,
-					  sdhci_am654->dll_enable);
+	ret = sdhci_am654_calculate_itap(host, fail_window, fail_index,
+					 sdhci_am654->dll_enable);
 
-	sdhci_am654_write_itapdly(sdhci_am654, itap, sdhci_am654->itap_del_ena[timing]);
+	if (ret >= 0) {
+		itap = ret;
+		sdhci_am654_write_itapdly(sdhci_am654, itap, sdhci_am654->itap_del_ena[timing]);
+	} else {
+		if (sdhci_am654->tuning_loop < RETRY_TUNING_MAX) {
+			sdhci_am654->tuning_loop++;
+			sdhci_am654_platform_execute_tuning(host, opcode);
+		} else {
+			return -1;
+		}
+	}
 
 	/* Save ITAPDLY */
 	sdhci_am654->itap_del_sel[timing] = itap;
@@ -908,6 +923,7 @@ static int sdhci_am654_probe(struct platform_device *pdev)
 		goto err_pltfm_free;
 	}
 
+	sdhci_am654->tuning_loop = 0;
 	host->mmc_host_ops.execute_tuning = sdhci_am654_execute_tuning;
 
 	pm_runtime_get_noresume(dev);
-- 
2.46.0