mmc: sdhci-cadence: Support mmc hardware reset

Add support for mmc hardware reset using a reset-controller
that would need to be enabled in the device tree with
a supporting driver.  The default is disabled for all
existing designs.

Signed-off-by: Brad Larson <blarson@amd.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>
Link: https://lore.kernel.org/r/20230410184526.15990-15-blarson@amd.com
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

diff --git a/drivers/mmc/host/sdhci-cadence.c b/drivers/mmc/host/sdhci-cadence.c
index 5d1e9cef74f5e3822a5ae72f1749ad37ce638391..b24aa27da50c40dd861212d8b7e7cfc848e962cd 100644 (file)
--- a/drivers/mmc/host/sdhci-cadence.c
+++ b/drivers/mmc/host/sdhci-cadence.c
@@ -12,6 +12,7 @@
 #include <linux/mmc/mmc.h>
 #include <linux/of.h>
 #include <linux/of_device.h>
+#include <linux/reset.h>
 
 #include "sdhci-pltfm.h"
 
@@ -70,6 +71,7 @@ struct sdhci_cdns_priv {
        spinlock_t wrlock;      /* write lock */
        bool enhanced_strobe;
        void (*priv_writel)(struct sdhci_cdns_priv *priv, u32 val, void __iomem *reg);
+       struct reset_control *rst_hw;
        unsigned int nr_phy_params;
        struct sdhci_cdns_phy_param phy_params[];
 };
@@ -457,6 +459,22 @@ static void sdhci_cdns_hs400_enhanced_strobe(struct mmc_host *mmc,
                                         SDHCI_CDNS_HRS06_MODE_MMC_HS400);
 }
 
+static void sdhci_cdns_mmc_hw_reset(struct mmc_host *mmc)
+{
+       struct sdhci_host *host = mmc_priv(mmc);
+       struct sdhci_cdns_priv *priv = sdhci_cdns_priv(host);
+
+       dev_dbg(mmc_dev(host->mmc), "emmc hardware reset\n");
+
+       reset_control_assert(priv->rst_hw);
+       /* For eMMC, minimum is 1us but give it 3us for good measure */
+       udelay(3);
+
+       reset_control_deassert(priv->rst_hw);
+       /* For eMMC, minimum is 200us but give it 300us for good measure */
+       usleep_range(300, 1000);
+}
+
 static int sdhci_cdns_probe(struct platform_device *pdev)
 {
        struct sdhci_host *host;
@@ -520,6 +538,15 @@ static int sdhci_cdns_probe(struct platform_device *pdev)
        if (ret)
                goto free;
 
+       if (host->mmc->caps & MMC_CAP_HW_RESET) {
+               priv->rst_hw = devm_reset_control_get_optional_exclusive(dev, NULL);
+               if (IS_ERR(priv->rst_hw))
+                       return dev_err_probe(mmc_dev(host->mmc), PTR_ERR(priv->rst_hw),
+                                            "reset controller error\n");
+               if (priv->rst_hw)
+                       host->mmc_host_ops.card_hw_reset = sdhci_cdns_mmc_hw_reset;
+       }
+
        ret = sdhci_add_host(host);
        if (ret)
                goto free;