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

Adrian Hunter
2026-05-05T14:05:49Z

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@gmail.com>

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@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);