mmc: tegra: Power on the calibration pad

Automatic pad drive strength calibration is performed on a separate pad
identical to the ones used for driving the actual bus. Power on the
calibration pad during the calibration procedure and power it off
afterwards to save power.
Signed-off-by: NAapo Vienamo <avienamo@nvidia.com>
Reviewed-by: NMikko Perttunen <mperttunen@nvidia.com>
Acked-by: NThierry Reding <treding@nvidia.com>
Acked-by: NAdrian Hunter <adrian.hunter@intel.com>
Signed-off-by: NUlf Hansson <ulf.hansson@linaro.org>

drivers/mmc/host/sdhci-tegra.c

@@ -54,6 +54,7 @@
 #define SDHCI_TEGRA_SDMEM_COMP_PADCTRL			0x1e0
 #define SDHCI_TEGRA_SDMEM_COMP_PADCTRL_VREF_SEL_MASK	0x0000000f
 #define SDHCI_TEGRA_SDMEM_COMP_PADCTRL_VREF_SEL_VAL	0x7
+#define SDHCI_TEGRA_SDMEM_COMP_PADCTRL_E_INPUT_E_PWRD	BIT(31)
 
 #define SDHCI_TEGRA_AUTO_CAL_STATUS			0x1ec
 #define SDHCI_TEGRA_AUTO_CAL_ACTIVE			BIT(31)
@@ -238,11 +239,34 @@ static void tegra_sdhci_reset(struct sdhci_host *host, u8 mask)
 	tegra_host->ddr_signaling = false;
 }
 
+static void tegra_sdhci_configure_cal_pad(struct sdhci_host *host, bool enable)
+{
+	u32 val;
+
+	/*
+	 * Enable or disable the additional I/O pad used by the drive strength
+	 * calibration process.
+	 */
+	val = sdhci_readl(host, SDHCI_TEGRA_SDMEM_COMP_PADCTRL);
+
+	if (enable)
+		val |= SDHCI_TEGRA_SDMEM_COMP_PADCTRL_E_INPUT_E_PWRD;
+	else
+		val &= ~SDHCI_TEGRA_SDMEM_COMP_PADCTRL_E_INPUT_E_PWRD;
+
+	sdhci_writel(host, val, SDHCI_TEGRA_SDMEM_COMP_PADCTRL);
+
+	if (enable)
+		usleep_range(1, 2);
+}
+
 static void tegra_sdhci_pad_autocalib(struct sdhci_host *host)
 {
 	u32 reg;
 	int ret;
 
+	tegra_sdhci_configure_cal_pad(host, true);
+
 	reg = sdhci_readl(host, SDHCI_TEGRA_AUTO_CAL_CONFIG);
 	reg |= SDHCI_AUTO_CAL_ENABLE | SDHCI_AUTO_CAL_START;
 	sdhci_writel(host, reg, SDHCI_TEGRA_AUTO_CAL_CONFIG);
@@ -253,6 +277,8 @@ static void tegra_sdhci_pad_autocalib(struct sdhci_host *host)
 				 reg, !(reg & SDHCI_TEGRA_AUTO_CAL_ACTIVE),
 				 1000, 10000);
 
+	tegra_sdhci_configure_cal_pad(host, false);
+
 	if (ret)
 		dev_err(mmc_dev(host->mmc), "Pad autocal timed out\n");
 }