linux-kernel - [PATCH 15/40] mmc: tegra: Power on the calibration pad

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Date:   Wed, 1 Aug 2018 19:32:05 +0300
From:   Aapo Vienamo <avienamo@...dia.com>
To:     Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Mikko Perttunen <mperttunen@...dia.com>,
        Stefan Agner <stefan@...er.ch>
CC:     <devicetree@...r.kernel.org>, <linux-tegra@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <linux-mmc@...r.kernel.org>,
        Aapo Vienamo <avienamo@...dia.com>
Subject: [PATCH 15/40] 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: Aapo Vienamo <avienamo@...dia.com>
Reviewed-by: Mikko Perttunen <mperttunen@...dia.com>
---
 drivers/mmc/host/sdhci-tegra.c | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/drivers/mmc/host/sdhci-tegra.c b/drivers/mmc/host/sdhci-tegra.c
index 53c035b9..9e22fec 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)
@@ -240,11 +241,32 @@ 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_SDMEM_COMP_PADCTRL_E_INPUT_E_PWRD;
+		sdhci_writel(host, reg, SDHCI_TEGRA_SDMEM_COMP_PADCTRL);
+		udelay(1);
+	} else {
+		reg &= ~SDHCI_TEGRA_SDMEM_COMP_PADCTRL_E_INPUT_E_PWRD;
+		sdhci_writel(host, reg, SDHCI_TEGRA_SDMEM_COMP_PADCTRL);
+	}
+}
+
 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);
@@ -254,6 +276,8 @@ static void tegra_sdhci_pad_autocalib(struct sdhci_host *host)
 				 reg, !(reg & SDHCI_TEGRA_AUTO_CAL_ACTIVE),
 				 1, 10000);
 
+	tegra_sdhci_configure_cal_pad(host, false);
+
 	if (ret)
 		dev_err(mmc_dev(host->mmc), "Pad autocal timed out\n");
 }
-- 
2.7.4