[PATCH v10 14/15] mmc: sdhci-cadence: Support mmc hardware reset

From: Brad Larson <blarson@amd.com>
To: <linux-arm-kernel@lists.infradead.org>
Cc: <linux-kernel@vger.kernel.org>, <linux-mmc@vger.kernel.org>,
	<linux-spi@vger.kernel.org>, <adrian.hunter@intel.com>,
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	<lee.jones@linaro.org>, <broonie@kernel.org>,
	<yamada.masahiro@socionext.com>, <p.zabel@pengutronix.de>,
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	<suravee.suthikulpanit@amd.com>, <thomas.lendacky@amd.com>,
	<tonyhuang.sunplus@gmail.com>, <ulf.hansson@linaro.org>,
	<vaishnav.a@ti.com>, <will@kernel.org>,
	<devicetree@vger.kernel.org>
Subject: [PATCH v10 14/15] mmc: sdhci-cadence: Support mmc hardware reset
Date: Sun, 5 Mar 2023 20:07:38 -0800	[thread overview]
Message-ID: <20230306040739.51488-15-blarson@amd.com> (raw)
In-Reply-To: <20230306040739.51488-1-blarson@amd.com>

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>
---

v9 changes:
- Previously patch 17/17
- Changed delay after reset_control_assert() from 9 to 3 usec
- Renamed sdhci_mmc_hw_reset() to sdhci_cdns_mmc_hw_reset()

---
 drivers/mmc/host/sdhci-cadence.c | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/drivers/mmc/host/sdhci-cadence.c b/drivers/mmc/host/sdhci-cadence.c
index 31c77d32aa7d..d13081da5e30 100644
--- 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[];
 };
@@ -460,6 +462,22 @@ 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;
@@ -523,6 +541,15 @@ 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, "hw");
+		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;
-- 
2.17.1

