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Subject[PATCH 03/10] mmc: tegra: Power on the calibration pad
Date
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@nvidia.com>
---
drivers/mmc/host/sdhci-tegra.c | 21 +++++++++++++++++++++
1 file changed, 21 insertions(+)

diff --git a/drivers/mmc/host/sdhci-tegra.c b/drivers/mmc/host/sdhci-tegra.c
index 6008e2f..61067b7 100644
--- a/drivers/mmc/host/sdhci-tegra.c
+++ b/drivers/mmc/host/sdhci-tegra.c
@@ -209,11 +209,30 @@ 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 reg;
+
+ /*
+ * Enable or disable the additional I/O pad used by the drive strength
+ * calibration process.
+ */
+ reg = sdhci_readl(host, SDHCI_TEGRA_SDMEM_COMP_PADCTRL);
+ if (enable)
+ reg |= SDHCI_TEGRA_PAD_E_INPUT_OR_E_PWRD;
+ else
+ reg &= ~SDHCI_TEGRA_PAD_E_INPUT_OR_E_PWRD;
+ sdhci_writel(host, reg, SDHCI_TEGRA_SDMEM_COMP_PADCTRL);
+ udelay(1);
+}
+
static void tegra_sdhci_pad_autocalib(struct sdhci_host *host)
{
unsigned timeout = 10;
u32 reg;

+ 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);
@@ -227,6 +246,8 @@ static void tegra_sdhci_pad_autocalib(struct sdhci_host *host)
timeout--;
} while (timeout);

+ tegra_sdhci_configure_cal_pad(host, false);
+
if (timeout == 0)
dev_err(mmc_dev(host->mmc), "Pad autocal timed out\n");
}
--
2.7.4
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