[PATCH v2] mmc: sdhci-of-dwcmshc: add reset control support in suspend/resume

[Artem Shimko <a.shimko.dev@gmail.com>]

The driver currently handles reset control only during initializations,
but does not manage the controller reset signal during system
suspend/resume. This can leave the hardware in an undefined state
after resume. Additionally, the reset control is stored in vendor
structs making it inaccessible for power management operations.

Move the reset control to dwcmshc_priv structure and add proper
assertion during suspend and deassertion during resume. The
needs_reset_on_pm flag to control whether reset operations are
performed during power management transitions, as not all platforms
require or support reset handling in suspend/resume path. This ensures the
controller is properly reset before entering low power state and correctly
reinitialized upon wake.

Signed-off-by: Artem Shimko <a.shimko.dev@gmail.com>
---

Hi,

Move reset control from vendor-specific private structures to the
common dwcmshc_priv. Introduce a needs_reset_on_pm flag — platforms
that require reset during suspend/resume set it to true. When the
flag is false (the default for all existing platforms), the PM path
behaves exactly as before, preserving full backward compatibility.

Rockchip RK35xx and EIC7700 do not set the flag; their suspend/resume
behaviour is unchanged.

--
Regards,
Artem

ChangeLog:
  v1:
    * https://lore.kernel.org/all/20260415123411.437450-1-a.shimko.dev@gmail.com/T/#u
  v2:
    * Added needs_reset_on_pm flag. The flag defaults to false,
      guaranteeing no functional change for existing platforms.

 drivers/mmc/host/sdhci-of-dwcmshc.c | 47 ++++++++++++++++++-----------
 1 file changed, 29 insertions(+), 18 deletions(-)

diff --git a/drivers/mmc/host/sdhci-of-dwcmshc.c b/drivers/mmc/host/sdhci-of-dwcmshc.c
index 0b2158a7e409..cf9be59f79c5 100644
--- a/drivers/mmc/host/sdhci-of-dwcmshc.c
+++ b/drivers/mmc/host/sdhci-of-dwcmshc.c
@@ -279,12 +279,10 @@
 #define PHY_DELAY_CODE_SD		0x55
 
 struct rk35xx_priv {
-	struct reset_control *reset;
 	u8 txclk_tapnum;
 };
 
 struct eic7700_priv {
-	struct reset_control *reset;
 	unsigned int drive_impedance;
 };
 
@@ -297,6 +295,8 @@ struct k230_priv  {
 
 struct dwcmshc_priv {
 	struct clk	*bus_clk;
+	struct reset_control *reset;
+	bool needs_reset_on_pm;
 	int vendor_specific_area1; /* P_VENDOR_SPECIFIC_AREA1 reg */
 	int vendor_specific_area2; /* P_VENDOR_SPECIFIC_AREA2 reg */
 
@@ -887,16 +887,15 @@ static void rk35xx_sdhci_reset(struct sdhci_host *host, u8 mask)
 {
 	struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
 	struct dwcmshc_priv *dwc_priv = sdhci_pltfm_priv(pltfm_host);
-	struct rk35xx_priv *priv = dwc_priv->priv;
 	u32 extra = sdhci_readl(host, DECMSHC_EMMC_MISC_CON);
 
 	if ((host->mmc->caps2 & MMC_CAP2_CQE) && (mask & SDHCI_RESET_ALL))
 		cqhci_deactivate(host->mmc);
 
-	if (mask & SDHCI_RESET_ALL && priv->reset) {
-		reset_control_assert(priv->reset);
+	if (mask & SDHCI_RESET_ALL && dwc_priv->reset) {
+		reset_control_assert(dwc_priv->reset);
 		udelay(1);
-		reset_control_deassert(priv->reset);
+		reset_control_deassert(dwc_priv->reset);
 	}
 
 	sdhci_reset(host, mask);
@@ -916,9 +915,9 @@ static int dwcmshc_rk35xx_init(struct device *dev, struct sdhci_host *host,
 	if (!priv)
 		return -ENOMEM;
 
-	priv->reset = devm_reset_control_array_get_optional_exclusive(mmc_dev(host->mmc));
-	if (IS_ERR(priv->reset)) {
-		err = PTR_ERR(priv->reset);
+	dwc_priv->reset = devm_reset_control_array_get_optional_exclusive(mmc_dev(host->mmc));
+	if (IS_ERR(dwc_priv->reset)) {
+		err = PTR_ERR(dwc_priv->reset);
 		dev_err(mmc_dev(host->mmc), "failed to get reset control %d\n", err);
 		return err;
 	}
@@ -1504,24 +1503,24 @@ static void sdhci_eic7700_reset(struct sdhci_host *host, u8 mask)
 		sdhci_eic7700_config_phy(host);
 }
 
-static int sdhci_eic7700_reset_init(struct device *dev, struct eic7700_priv *priv)
+static int sdhci_eic7700_reset_init(struct device *dev, struct dwcmshc_priv *dwc_priv)
 {
 	int ret;
 
-	priv->reset = devm_reset_control_array_get_optional_exclusive(dev);
-	if (IS_ERR(priv->reset)) {
-		ret = PTR_ERR(priv->reset);
+	dwc_priv->reset = devm_reset_control_array_get_optional_exclusive(dev);
+	if (IS_ERR(dwc_priv->reset)) {
+		ret = PTR_ERR(dwc_priv->reset);
 		dev_err(dev, "failed to get reset control %d\n", ret);
 		return ret;
 	}
 
-	ret = reset_control_assert(priv->reset);
+	ret = reset_control_assert(dwc_priv->reset);
 	if (ret) {
 		dev_err(dev, "Failed to assert reset signals: %d\n", ret);
 		return ret;
 	}
 	usleep_range(2000, 2100);
-	ret = reset_control_deassert(priv->reset);
+	ret = reset_control_deassert(dwc_priv->reset);
 	if (ret) {
 		dev_err(dev, "Failed to deassert reset signals: %d\n", ret);
 		return ret;
@@ -1780,7 +1779,7 @@ static int eic7700_init(struct device *dev, struct sdhci_host *host, struct dwcm
 
 	dwc_priv->priv = priv;
 
-	ret = sdhci_eic7700_reset_init(dev, dwc_priv->priv);
+	ret = sdhci_eic7700_reset_init(dev, dwc_priv);
 	if (ret) {
 		dev_err(dev, "failed to reset\n");
 		return ret;
@@ -2563,6 +2562,9 @@ static int dwcmshc_suspend(struct device *dev)
 	if (ret)
 		return ret;
 
+	if (priv->needs_reset_on_pm)
+		reset_control_assert(priv->reset);
+
 	clk_disable_unprepare(pltfm_host->clk);
 	if (!IS_ERR(priv->bus_clk))
 		clk_disable_unprepare(priv->bus_clk);
@@ -2593,18 +2595,27 @@ static int dwcmshc_resume(struct device *dev)
 	if (ret)
 		goto disable_bus_clk;
 
+	if (priv->needs_reset_on_pm) {
+		ret = reset_control_deassert(priv->reset);
+		if (ret)
+			goto disable_other_clks;
+	}
+
 	ret = sdhci_resume_host(host);
 	if (ret)
-		goto disable_other_clks;
+		goto assert_reset;
 
 	if (host->mmc->caps2 & MMC_CAP2_CQE) {
 		ret = cqhci_resume(host->mmc);
 		if (ret)
-			goto disable_other_clks;
+			goto assert_reset;
 	}
 
 	return 0;
 
+assert_reset:
+	if (priv->needs_reset_on_pm)
+		reset_control_assert(priv->reset);
 disable_other_clks:
 	clk_bulk_disable_unprepare(priv->num_other_clks, priv->other_clks);
 disable_bus_clk:
-- 
2.43.0