linux-kernel - [PATCH v1 6/6] sdhci: tegra: Add missing TMCLK for data timeout

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Message-ID: <1596483863-22153-7-git-send-email-skomatineni@nvidia.com>
Date:   Mon, 3 Aug 2020 12:44:23 -0700
From:   Sowjanya Komatineni <skomatineni@...dia.com>
To:     <adrian.hunter@...el.com>, <ulf.hansson@...aro.org>,
        <thierry.reding@...il.com>, <jonathanh@...dia.com>,
        <robh+dt@...nel.org>
CC:     <skomatineni@...dia.com>, <devicetree@...r.kernel.org>,
        <linux-tegra@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-mmc@...r.kernel.org>
Subject: [PATCH v1 6/6] sdhci: tegra: Add missing TMCLK for data timeout

commit b5a84ecf025a ("mmc: tegra: Add Tegra210 support")

Tegra210 and later has a separate sdmmc_legacy_tm (TMCLK) used by Tegra
SDMMC hawdware for data timeout to achive better timeout than using
SDCLK and using TMCLK is recommended.

USE_TMCLK_FOR_DATA_TIMEOUT bit in Tegra SDMMC register
SDHCI_TEGRA_VENDOR_SYS_SW_CTRL can be used to choose either TMCLK or
SDCLK for data timeout.

Default USE_TMCLK_FOR_DATA_TIMEOUT bit is set to 1 and TMCLK is used
for data timeout by Tegra SDMMC hardware and having TMCLK not enabled
is not recommended.

So, this patch fixes it.

Signed-off-by: Sowjanya Komatineni <skomatineni@...dia.com>
---
 drivers/mmc/host/sdhci-tegra.c | 41 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 41 insertions(+)

diff --git a/drivers/mmc/host/sdhci-tegra.c b/drivers/mmc/host/sdhci-tegra.c
index 31ed321..39e2195 100644
--- a/drivers/mmc/host/sdhci-tegra.c
+++ b/drivers/mmc/host/sdhci-tegra.c
@@ -140,6 +140,7 @@ struct sdhci_tegra_autocal_offsets {
 struct sdhci_tegra {
 	const struct sdhci_tegra_soc_data *soc_data;
 	struct gpio_desc *power_gpio;
+	struct clk *tmclk;
 	bool ddr_signaling;
 	bool pad_calib_required;
 	bool pad_control_available;
@@ -1611,6 +1612,44 @@ static int sdhci_tegra_probe(struct platform_device *pdev)
 		goto err_power_req;
 	}
 
+	/*
+	 * Tegra210 has a separate SDMMC_LEGACY_TM clock used for host
+	 * timeout clock and SW can choose TMCLK or SDCLK for hardware
+	 * data timeout through the bit USE_TMCLK_FOR_DATA_TIMEOUT of
+	 * the register SDHCI_TEGRA_VENDOR_SYS_SW_CTRL.
+	 *
+	 * USE_TMCLK_FOR_DATA_TIMEOUT bit default is set to 1 and SDMMC uses
+	 * 12Mhz TMCLK which is advertised in host capability register.
+	 * With TMCLK of 12Mhz provides maximum data timeout period that can
+	 * be achieved is 11s better than using SDCLK for data timeout.
+	 *
+	 * So, TMCLK is set to 12Mhz and kept enabled all the time on SoC's
+	 * supporting SDR104 mode and when not using SDCLK for data timeout.
+	 */
+
+	if ((soc_data->nvquirks & NVQUIRK_ENABLE_SDR104) &&
+	    (!soc_data->pdata->quirks & SDHCI_QUIRK_DATA_TIMEOUT_USES_SDCLK)) {
+		clk = devm_clk_get(&pdev->dev, "tmclk");
+		if (IS_ERR(clk)) {
+			rc = PTR_ERR(clk);
+			if (rc == -EPROBE_DEFER)
+				goto err_power_req;
+
+			dev_warn(&pdev->dev, "failed to get tmclk: %d\n", rc);
+			clk = NULL;
+		}
+
+		clk_set_rate(clk, 12000000);
+		rc = clk_prepare_enable(clk);
+		if (rc) {
+			dev_err(&pdev->dev,
+				"failed to enable tmclk: %d\n", rc);
+			goto err_power_req;
+		}
+
+		tegra_host->tmclk = clk;
+	}
+
 	clk = devm_clk_get(mmc_dev(host->mmc), NULL);
 	if (IS_ERR(clk)) {
 		rc = PTR_ERR(clk);
@@ -1654,6 +1693,7 @@ static int sdhci_tegra_probe(struct platform_device *pdev)
 err_rst_get:
 	clk_disable_unprepare(pltfm_host->clk);
 err_clk_get:
+	clk_disable_unprepare(tegra_host->tmclk);
 err_power_req:
 err_parse_dt:
 	sdhci_pltfm_free(pdev);
@@ -1671,6 +1711,7 @@ static int sdhci_tegra_remove(struct platform_device *pdev)
 	reset_control_assert(tegra_host->rst);
 	usleep_range(2000, 4000);
 	clk_disable_unprepare(pltfm_host->clk);
+	clk_disable_unprepare(tegra_host->tmclk);
 
 	sdhci_pltfm_free(pdev);
 
-- 
2.7.4