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

[Adrian Hunter]

On 05/05/2026 16:37, Artem Shimko wrote:
> 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@xxxxxxxxx>

Changes cannot be accepted unless there is a user for new
functionality i.e. you must add support for a device that
has needs_reset_on_pm set to true.

> ---
> 
> 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@xxxxxxxxx/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: