linux-kernel - [PATCH v4] mmc: sdhci-tegra: Fix switch to HS400ES mode

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Message-ID: <20211214113653.4631-1-pshete@nvidia.com>
Date:   Tue, 14 Dec 2021 17:06:53 +0530
From:   Prathamesh Shete <pshete@...dia.com>
To:     <adrian.hunter@...el.com>, <ulf.hansson@...aro.org>,
        <thierry.reding@...il.com>, <jonathanh@...dia.com>,
        <p.zabel@...gutronix.de>, <linux-mmc@...r.kernel.org>,
        <linux-tegra@...r.kernel.org>, <linux-kernel@...r.kernel.org>
CC:     <pshete@...dia.com>, <anrao@...dia.com>, <smangipudi@...dia.com>
Subject: [PATCH v4] mmc: sdhci-tegra: Fix switch to HS400ES mode

When CMD13 is sent after switching to HS400ES mode, the bus
is operating at either MMC_HIGH_26_MAX_DTR or MMC_HIGH_52_MAX_DTR.
To meet Tegra SDHCI requirement at HS400ES mode, force SDHCI
interface clock to MMC_HS200_MAX_DTR (200 MHz) so that host
controller CAR clock and the interface clock are rate matched.

Signed-off-by: Prathamesh Shete <pshete@...dia.com>
---
 drivers/mmc/host/sdhci-tegra.c | 43 ++++++++++++++++++++--------------
 1 file changed, 26 insertions(+), 17 deletions(-)

diff --git a/drivers/mmc/host/sdhci-tegra.c b/drivers/mmc/host/sdhci-tegra.c
index 387ce9cdbd7c..7be6674eebd5 100644
--- a/drivers/mmc/host/sdhci-tegra.c
+++ b/drivers/mmc/host/sdhci-tegra.c
@@ -354,23 +354,6 @@ static void tegra_sdhci_set_tap(struct sdhci_host *host, unsigned int tap)
 	}
 }
 
-static void tegra_sdhci_hs400_enhanced_strobe(struct mmc_host *mmc,
-					      struct mmc_ios *ios)
-{
-	struct sdhci_host *host = mmc_priv(mmc);
-	u32 val;
-
-	val = sdhci_readl(host, SDHCI_TEGRA_VENDOR_SYS_SW_CTRL);
-
-	if (ios->enhanced_strobe)
-		val |= SDHCI_TEGRA_SYS_SW_CTRL_ENHANCED_STROBE;
-	else
-		val &= ~SDHCI_TEGRA_SYS_SW_CTRL_ENHANCED_STROBE;
-
-	sdhci_writel(host, val, SDHCI_TEGRA_VENDOR_SYS_SW_CTRL);
-
-}
-
 static void tegra_sdhci_reset(struct sdhci_host *host, u8 mask)
 {
 	struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
@@ -791,6 +774,32 @@ static void tegra_sdhci_set_clock(struct sdhci_host *host, unsigned int clock)
 	}
 }
 
+static void tegra_sdhci_hs400_enhanced_strobe(struct mmc_host *mmc,
+					      struct mmc_ios *ios)
+{
+	struct sdhci_host *host = mmc_priv(mmc);
+	u32 val;
+
+	val = sdhci_readl(host, SDHCI_TEGRA_VENDOR_SYS_SW_CTRL);
+
+	if (ios->enhanced_strobe) {
+		val |= SDHCI_TEGRA_SYS_SW_CTRL_ENHANCED_STROBE;
+		/*
+		 * When CMD13 is sent from mmc_select_hs400es() after
+		 * switching to HS400ES mode, the bus is operating at
+		 * either MMC_HIGH_26_MAX_DTR or MMC_HIGH_52_MAX_DTR.
+		 * To meet Tegra SDHCI requirement at HS400ES mode, force SDHCI
+		 * interface clock to MMC_HS200_MAX_DTR (200 MHz) so that host
+		 * controller CAR clock and the interface clock are rate matched.
+		 */
+		tegra_sdhci_set_clock(host, MMC_HS200_MAX_DTR);
+	} else {
+		val &= ~SDHCI_TEGRA_SYS_SW_CTRL_ENHANCED_STROBE;
+	}
+
+	sdhci_writel(host, val, SDHCI_TEGRA_VENDOR_SYS_SW_CTRL);
+}
+
 static unsigned int tegra_sdhci_get_max_clock(struct sdhci_host *host)
 {
 	struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
-- 
2.17.1