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 <avienamo@xxxxxxxxxx>
Reviewed-by: Mikko Perttunen <mperttunen@xxxxxxxxxx>
Acked-by: Thierry Reding <treding@xxxxxxxxxx>
---
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
