[PATCH v13 14/15] mmc: sdhci-cadence: Support mmc hardware reset

Brad Larson
2023-04-10T18:49:01Z

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>
---

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 5d1e9cef74f5..b24aa27da50c 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[];
};
@@ -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;
--
2.17.1