mmc: sdhci: Control the delay between tuning commands

The delay between tuning commands for SD cards is not part of the
specification. A driver that needs it probably needs it for eMMC
too, whereas most drivers would probably like to set it to 0. Make
it a host member (host->tuning_delay) that defaults to the existing
behaviour. Drivers can set it to zero to eliminate the delay, or
set it to a positive value to always have a delay.
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Yangbo Lu <yangbo.lu@nxp.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

drivers/mmc/host/sdhci.c

@@ -2108,9 +2108,9 @@ static void __sdhci_execute_tuning(struct sdhci_host *host, u32 opcode)
 			break;
 		}
 
-		/* eMMC spec does not require a delay between tuning cycles */
-		if (opcode == MMC_SEND_TUNING_BLOCK)
-			mdelay(1);
+		/* Spec does not require a delay between tuning cycles */
+		if (host->tuning_delay > 0)
+			mdelay(host->tuning_delay);
 	}
 
 	pr_info("%s: Tuning failed, falling back to fixed sampling clock\n",
@@ -2172,6 +2172,9 @@ int sdhci_execute_tuning(struct mmc_host *mmc, u32 opcode)
 
 	host->mmc->retune_period = tuning_count;
 
+	if (host->tuning_delay < 0)
+		host->tuning_delay = opcode == MMC_SEND_TUNING_BLOCK;
+
 	sdhci_start_tuning(host);
 
 	__sdhci_execute_tuning(host, opcode);
@@ -3114,6 +3117,8 @@ struct sdhci_host *sdhci_alloc_host(struct device *dev,
 	host->cqe_ier     = SDHCI_CQE_INT_MASK;
 	host->cqe_err_ier = SDHCI_CQE_INT_ERR_MASK;
 
+	host->tuning_delay = -1;
+
 	return host;
 }
 

drivers/mmc/host/sdhci.h

@@ -538,6 +538,8 @@ struct sdhci_host {
 #define SDHCI_TUNING_MODE_1	0
 #define SDHCI_TUNING_MODE_2	1
 #define SDHCI_TUNING_MODE_3	2
+	/* Delay (ms) between tuning commands */
+	int			tuning_delay;
 
 	unsigned long private[0] ____cacheline_aligned;
 };