mmc: tegra: Implement HS400 enhanced strobe

Implement eMMC HS400 enhanced strobe. Enhanced strobe is an alternative
mechanism to the HS400 tuning procedure.
Signed-off-by: NAapo Vienamo <avienamo@nvidia.com>
Acked-by: NAdrian Hunter <adrian.hunter@intel.com>
Acked-by: NThierry Reding <treding@nvidia.com>
Signed-off-by: NUlf Hansson <ulf.hansson@linaro.org>

drivers/mmc/host/sdhci-tegra.c

@@ -43,6 +43,9 @@
 #define SDHCI_CLOCK_CTRL_PADPIPE_CLKEN_OVERRIDE		BIT(3)
 #define SDHCI_CLOCK_CTRL_SPI_MODE_CLKEN_OVERRIDE	BIT(2)
 
+#define SDHCI_TEGRA_VENDOR_SYS_SW_CTRL			0x104
+#define SDHCI_TEGRA_SYS_SW_CTRL_ENHANCED_STROBE		BIT(31)
+
 #define SDHCI_TEGRA_VENDOR_CAP_OVERRIDES		0x10c
 #define SDHCI_TEGRA_CAP_OVERRIDES_DQS_TRIM_MASK		0x00003f00
 #define SDHCI_TEGRA_CAP_OVERRIDES_DQS_TRIM_SHIFT	8
@@ -294,6 +297,23 @@ static void tegra_sdhci_set_tap(struct sdhci_host *host, unsigned int tap)
 	}
 }
 
+static void tegra_sdhci_hs400_enhanced_strobe(struct mmc_host *mmc,
+					      struct mmc_ios *ios)
+{
+	struct sdhci_host *host = mmc_priv(mmc);
+	u32 val;
+
+	val = sdhci_readl(host, SDHCI_TEGRA_VENDOR_SYS_SW_CTRL);
+
+	if (ios->enhanced_strobe)
+		val |= SDHCI_TEGRA_SYS_SW_CTRL_ENHANCED_STROBE;
+	else
+		val &= ~SDHCI_TEGRA_SYS_SW_CTRL_ENHANCED_STROBE;
+
+	sdhci_writel(host, val, SDHCI_TEGRA_VENDOR_SYS_SW_CTRL);
+
+}
+
 static void tegra_sdhci_reset(struct sdhci_host *host, u8 mask)
 {
 	struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
@@ -996,6 +1016,9 @@ static int sdhci_tegra_probe(struct platform_device *pdev)
 				sdhci_tegra_start_signal_voltage_switch;
 	}
 
+	host->mmc_host_ops.hs400_enhanced_strobe =
+			tegra_sdhci_hs400_enhanced_strobe;
+
 	rc = mmc_of_parse(host->mmc);
 	if (rc)
 		goto err_parse_dt;