linux-kernel - [PATCH] mmc: sdhci-of-at91: force card detect value for non removable devices

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Message-ID: <20170726140246.4775-1-ludovic.desroches@microchip.com>
Date:   Wed, 26 Jul 2017 16:02:46 +0200
From:   Ludovic Desroches <ludovic.desroches@...rochip.com>
To:     <linux-mmc@...r.kernel.org>
CC:     <adrian.hunter@...el.com>, <ulf.hansson@...aro.org>,
        <linux-kernel@...r.kernel.org>,
        <alexandre.belloni@...e-electrons.com>,
        <nicolas.ferre@...rochip.com>,
        Ludovic Desroches <ludovic.desroches@...rochip.com>
Subject: [PATCH] mmc: sdhci-of-at91: force card detect value for non removable devices

When the device is non removable, the card detect signal is often use
for another purpose i.e. muxed to another SoC peripheral or used as a
GPIO. It could lead to wrong behaviors depending the defaut value of
this signal if not muxed to the SDHCI controller.

Fixes: bb5f8ea4d514 ("mmc: sdhci-of-at91: introduce driver for the Atmel SDMMC")
Signed-off-by: Ludovic Desroches <ludovic.desroches@...rochip.com>
---
 drivers/mmc/host/sdhci-of-at91.c | 36 +++++++++++++++++++++++++++++++++++-
 1 file changed, 35 insertions(+), 1 deletion(-)

diff --git a/drivers/mmc/host/sdhci-of-at91.c b/drivers/mmc/host/sdhci-of-at91.c
index 88e9b5f35a62..6a389f35396e 100644
--- a/drivers/mmc/host/sdhci-of-at91.c
+++ b/drivers/mmc/host/sdhci-of-at91.c
@@ -31,6 +31,7 @@
 
 #define SDMMC_MC1R	0x204
 #define		SDMMC_MC1R_DDR		BIT(3)
+#define		SDMMC_MC1R_FCD		BIT(7)
 #define SDMMC_CACR	0x230
 #define		SDMMC_CACR_CAPWREN	BIT(0)
 #define		SDMMC_CACR_KEY		(0x46 << 8)
@@ -44,6 +45,15 @@ struct sdhci_at91_priv {
 	bool restore_needed;
 };
 
+static void sdhci_at91_set_force_card_detect(struct sdhci_host *host)
+{
+	u8 mc1r;
+
+	mc1r = readb(host->ioaddr + SDMMC_MC1R);
+	mc1r |= SDMMC_MC1R_FCD;
+	writeb(mc1r, host->ioaddr + SDMMC_MC1R);
+}
+
 static void sdhci_at91_set_clock(struct sdhci_host *host, unsigned int clock)
 {
 	u16 clk;
@@ -111,10 +121,18 @@ void sdhci_at91_set_uhs_signaling(struct sdhci_host *host, unsigned int timing)
 	sdhci_set_uhs_signaling(host, timing);
 }
 
+static void sdhci_at91_reset(struct sdhci_host *host, u8 mask)
+{
+	sdhci_reset(host, mask);
+
+	if (host->mmc->caps & MMC_CAP_NONREMOVABLE)
+		sdhci_at91_set_force_card_detect(host);
+}
+
 static const struct sdhci_ops sdhci_at91_sama5d2_ops = {
 	.set_clock		= sdhci_at91_set_clock,
 	.set_bus_width		= sdhci_set_bus_width,
-	.reset			= sdhci_reset,
+	.reset			= sdhci_at91_reset,
 	.set_uhs_signaling	= sdhci_at91_set_uhs_signaling,
 	.set_power		= sdhci_at91_set_power,
 };
@@ -369,6 +387,22 @@ static int sdhci_at91_probe(struct platform_device *pdev)
 		host->quirks &= ~SDHCI_QUIRK_BROKEN_CARD_DETECTION;
 	}
 
+	/*
+	 * If the device attached to the MMC bus is not removable, it is safer
+	 * to set the Force Card Detect bit. People often don't connect the
+	 * card detect signal and use this pin for another purpose. If the card
+	 * detect pin is not muxed to SDHCI controller, a default value is
+	 * used. This value can be different from a SoC revision to another
+	 * one. Problems come when this default value is not card present. To
+	 * avoid this case, if the device is non removable then the card
+	 * detection procedure using the SDMCC_CD signal is bypassed.
+	 * This bit is resetted when a software reset for all command is
+	 * performed so we need to implement our own reset function to set back
+	 * this bit.
+	 */
+	if (host->mmc->caps & MMC_CAP_NONREMOVABLE)
+		sdhci_at91_set_force_card_detect(host);
+
 	pm_runtime_put_autosuspend(&pdev->dev);
 
 	return 0;
-- 
2.12.2