[PATCH v2 03/10] mmc: tegra: Power on the calibration pad

From: Aapo Vienamo <avienamo@nvidia.com>
To: Ulf Hansson <ulf.hansson@linaro.org>,
	Rob Herring <robh+dt@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Thierry Reding <thierry.reding@gmail.com>,
	Jonathan Hunter <jonathanh@nvidia.com>,
	Adrian Hunter <adrian.hunter@intel.com>,
	Mikko Perttunen <mperttunen@nvidia.com>
Cc: linux-mmc@vger.kernel.org, devicetree@vger.kernel.org,
	linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org,
	Aapo Vienamo <avienamo@nvidia.com>
Subject: [PATCH v2 03/10] mmc: tegra: Power on the calibration pad
Date: Thu, 26 Jul 2018 15:26:49 +0300	[thread overview]
Message-ID: <1532608016-14319-4-git-send-email-avienamo@nvidia.com> (raw)
In-Reply-To: <1532608016-14319-1-git-send-email-avienamo@nvidia.com>

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>
Reviewed-by: Mikko Perttunen <mperttunen@nvidia.com>
---
 drivers/mmc/host/sdhci-tegra.c | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/drivers/mmc/host/sdhci-tegra.c b/drivers/mmc/host/sdhci-tegra.c
index 51eda20..363490e 100644
--- a/drivers/mmc/host/sdhci-tegra.c
+++ b/drivers/mmc/host/sdhci-tegra.c
@@ -53,6 +53,7 @@
 #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)
@@ -241,11 +242,30 @@ 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_SDMEM_COMP_PADCTRL_E_INPUT_E_PWRD;
+	else
+		reg &= ~SDHCI_TEGRA_SDMEM_COMP_PADCTRL_E_INPUT_E_PWRD;
+	sdhci_writel(host, reg, SDHCI_TEGRA_SDMEM_COMP_PADCTRL);
+	udelay(1);
+}
+
 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);
@@ -255,6 +275,8 @@ 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
