Re: [PATCH] mmc: sdhci-of-at91: disable selectively clocks on pm runtime

[Robert Marko]

On Fri, Sep 18, 2026 at 5:35 PM Aubin Constans
<aubin.constans@xxxxxxxxxxxxx> wrote:
>
> From: Claudiu Beznea <claudiu.beznea@xxxxxxxxx>
>
> SAMA7G5's SDMMC run-time clock disabling is not supported.
> Add support to avoid this scenario for SAMA7G5.
>
> [Amended with a fix from Romain Sioen below this line]
>
> Sama7 boards are impacted by an unbalanced prepare/unprepare
> and enable/disable clock management in sdhci driver due to
> the lack of support for SDMMC clock runtime disabling,
> managed instead by the PMC driver.
>
> Add conditions in the preset function to manage clock
> depending on if the board support runtime clock disabling
> and if we come from the probing or restoring procedure.
>
> Add boolean start_clks variable to manage condition
> in preset function.
>
> Signed-off-by: Claudiu Beznea <claudiu.beznea@xxxxxxxxx>
> Co-developed-by: Romain Sioen <romain.sioen@xxxxxxxxxxxxx>
> Signed-off-by: Romain Sioen <romain.sioen@xxxxxxxxxxxxx>
> Signed-off-by: Aubin Constans <aubin.constans@xxxxxxxxxxxxx>

Tested-by: Robert Marko <robert.marko@xxxxxxxxxx>

> ---
>  drivers/mmc/host/sdhci-of-at91.c | 36 ++++++++++++++++++++++++--------
>  1 file changed, 27 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/mmc/host/sdhci-of-at91.c b/drivers/mmc/host/sdhci-of-at91.c
> index 7c4ac65f247d..399856643e57 100644
> --- a/drivers/mmc/host/sdhci-of-at91.c
> +++ b/drivers/mmc/host/sdhci-of-at91.c
> @@ -39,6 +39,7 @@ struct sdhci_at91_soc_data {
>         const struct sdhci_pltfm_data *pdata;
>         bool baseclk_is_generated_internally;
>         unsigned int divider_for_baseclk;
> +       bool pm_runtime_disable_clks;
>  };
>
>  struct sdhci_at91_priv {
> @@ -149,12 +150,14 @@ static const struct sdhci_pltfm_data sdhci_sama5d2_pdata = {
>  static const struct sdhci_at91_soc_data soc_data_sama5d2 = {
>         .pdata = &sdhci_sama5d2_pdata,
>         .baseclk_is_generated_internally = false,
> +       .pm_runtime_disable_clks = true,
>  };
>
>  static const struct sdhci_at91_soc_data soc_data_sam9x60 = {
>         .pdata = &sdhci_sama5d2_pdata,
>         .baseclk_is_generated_internally = true,
>         .divider_for_baseclk = 2,
> +       .pm_runtime_disable_clks = true,
>  };
>
>  static const struct of_device_id sdhci_at91_dt_match[] = {
> @@ -164,7 +167,7 @@ static const struct of_device_id sdhci_at91_dt_match[] = {
>  };
>  MODULE_DEVICE_TABLE(of, sdhci_at91_dt_match);
>
> -static int sdhci_at91_set_clks_presets(struct device *dev)
> +static int sdhci_at91_set_clks_presets(struct device *dev, bool start_clks)
>  {
>         struct sdhci_host *host = dev_get_drvdata(dev);
>         struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
> @@ -174,7 +177,14 @@ static int sdhci_at91_set_clks_presets(struct device *dev)
>         unsigned int                    gck_rate, clk_base_rate;
>         unsigned int                    preset_div;
>
> -       clk_prepare_enable(priv->hclock);
> +       /*
> +        * Manage clock prepare/enable procedure depending on if the board
> +        * support runtime clock disabling and if we come from the probing
> +        * or restoring procedure (for backup+self refresh).
> +        */
> +       if (start_clks)
> +               clk_prepare_enable(priv->hclock);
> +
>         caps0 = readl(host->ioaddr + SDHCI_CAPABILITIES);
>         caps1 = readl(host->ioaddr + SDHCI_CAPABILITIES_1);
>
> @@ -223,8 +233,11 @@ static int sdhci_at91_set_clks_presets(struct device *dev)
>         writew(SDHCI_AT91_PRESET_COMMON_CONF | preset_div,
>                host->ioaddr + SDHCI_PRESET_FOR_DDR50);
>
> -       clk_prepare_enable(priv->mainck);
> -       clk_prepare_enable(priv->gck);
> +       /* Same clock management as for hclock */
> +       if (start_clks) {
> +               clk_prepare_enable(priv->mainck);
> +               clk_prepare_enable(priv->gck);
> +       }
>
>         return 0;
>  }
> @@ -254,9 +267,11 @@ static int sdhci_at91_runtime_suspend(struct device *dev)
>         if (host->tuning_mode != SDHCI_TUNING_MODE_3)
>                 mmc_retune_needed(host->mmc);
>
> -       clk_disable_unprepare(priv->gck);
> -       clk_disable_unprepare(priv->hclock);
> -       clk_disable_unprepare(priv->mainck);
> +       if (priv->soc_data->pm_runtime_disable_clks) {
> +               clk_disable_unprepare(priv->gck);
> +               clk_disable_unprepare(priv->hclock);
> +               clk_disable_unprepare(priv->mainck);
> +       }
>
>         return 0;
>  }
> @@ -269,7 +284,7 @@ static int sdhci_at91_runtime_resume(struct device *dev)
>         int ret;
>
>         if (priv->restore_needed) {
> -               ret = sdhci_at91_set_clks_presets(dev);
> +               ret = sdhci_at91_set_clks_presets(dev, priv->soc_data->pm_runtime_disable_clks);
>                 if (ret)
>                         return ret;
>
> @@ -277,6 +292,9 @@ static int sdhci_at91_runtime_resume(struct device *dev)
>                 goto out;
>         }
>
> +       if (!priv->soc_data->pm_runtime_disable_clks)
> +               goto out;
> +
>         ret = clk_prepare_enable(priv->mainck);
>         if (ret) {
>                 dev_err(dev, "can't enable mainck\n");
> @@ -344,7 +362,7 @@ static int sdhci_at91_probe(struct platform_device *pdev)
>                 return dev_err_probe(&pdev->dev, PTR_ERR(priv->gck),
>                                      "failed to get multclk\n");
>
> -       ret = sdhci_at91_set_clks_presets(&pdev->dev);
> +       ret = sdhci_at91_set_clks_presets(&pdev->dev, true);
>         if (ret)
>                 return ret;
>
> --
> 2.43.0
>


-- 
Robert Marko
Staff Embedded Linux Engineer
Sartura d.d.
Lendavska ulica 16a
10000 Zagreb, Croatia
Email: robert.marko@xxxxxxxxxx
Web: www.sartura.hr