[PATCH v3 14/38] mmc: tegra: Power on the calibration pad

[Aapo Vienamo]

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: Aapo Vienamo <avien...@nvidia.com>
Reviewed-by: Mikko Perttunen <mperttu...@nvidia.com>
Acked-by: Thierry Reding <tred...@nvidia.com>
---
 drivers/mmc/host/sdhci-tegra.c | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/drivers/mmc/host/sdhci-tegra.c b/drivers/mmc/host/sdhci-tegra.c
index 01a21e0af6d7..e63cd6b2fc9f 100644
--- a/drivers/mmc/host/sdhci-tegra.c
+++ b/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");
 }
-- 
2.18.0