[PATCH v2 2/6] mmc: sdhci-of-at91: add option to keep clocks enabled
Robert Marko
robert.marko at sartura.hr
Tue Sep 22 05:10:56 PDT 2026
On Fri, Sep 18, 2026 at 6:02 PM Aubin Constans
<aubin.constans at microchip.com> wrote:
>
> On 15/09/2026 13:31, Robert Marko wrote:
> > On Mon, Sep 14, 2026 at 3:46 PM Aubin Constans
> > <aubin.constans at microchip.com> wrote:
> >>
> >> Hi Robert,
> >>
> >> On 07/09/2026 15:25, Robert Marko wrote:
> >>> sdhci_at91_set_clks_presets() both enables the controller clocks and
> >>> programs its capabilities and preset registers. This prevents callers from
> >>> restoring the registers without changing the clock enable counts.
> >>>
> >>> Move clock enablement to callers and add a SoC data flag for controllers
> >>> that must keep their clocks enabled. Use it in the runtime PM paths while
> >>> keeping register restoration separate from clock enablement.
> >>
> >> This change has been required for the SAMA7G54 MPU already, and implemented by
> >> two complementary commits:
> >>
> >> https://github.com/linux4microchip/linux/commit/763a3c05c8f9d0feb279c6f308fa5d48d14e07d3
> >> https://github.com/linux4microchip/linux/commit/b5bbc888fb39471d46fe0a4ff28f69533c265dd0
> >>
> >> At least they have been validated by test campaigns.
> >> If that existing work seemed OK for you and the LAN969x, then I could squash
> >> these two commits and submit the result.
> >
> > Hi Aubin,
> > Yeah, I originally used those in our tree as well before trying to
> > simplify things for upstreaming.
> >
> > Regards,
> > Robert
> >
>
> To follow up on that patch, I have just submitted the original work,
> ported to tag next-20260917:
>
> https://lore.kernel.org/linux-mmc/20260918153414.909333-1-aubin.constans@microchip.com/
>
> Hope it will make easier to support the LAN969x, notably.
Hi Aubin,
As long as that is merged, then LAN969x support is really simple.
I tested it locally and it works, so I am waiting on that getting
merged before sending v3 for LAN969x.
Regards,
Robert
>
> Regards,
> Aubin
>
> >>>
> >>> Signed-off-by: Robert Marko <robert.marko at sartura.hr>
> >>>
> >>> drivers/mmc/host/sdhci-of-at91.c | 39 +++++++++++++++++++-------------
> >>> 1 file changed, 23 insertions(+), 16 deletions(-)
> >>>
> >>> diff --git a/drivers/mmc/host/sdhci-of-at91.c b/drivers/mmc/host/sdhci-of-at91.c
> >>> index 7c4ac65f247d..b7e2a89da348 100644
> >>> --- a/drivers/mmc/host/sdhci-of-at91.c
> >>> +++ b/drivers/mmc/host/sdhci-of-at91.c
> >>> @@ -38,6 +38,7 @@
> >>> struct sdhci_at91_soc_data {
> >>> const struct sdhci_pltfm_data *pdata;
> >>> bool baseclk_is_generated_internally;
> >>> + bool keep_clks_on;
> >>> unsigned int divider_for_baseclk;
> >>> };
> >>>
> >>> @@ -164,7 +165,7 @@ 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 void sdhci_at91_set_clks_presets(struct device *dev)
> >>> {
> >>> struct sdhci_host *host = dev_get_drvdata(dev);
> >>> struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
> >>> @@ -174,7 +175,6 @@ 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);
> >>> caps0 = readl(host->ioaddr + SDHCI_CAPABILITIES);
> >>> caps1 = readl(host->ioaddr + SDHCI_CAPABILITIES_1);
> >>>
> >>> @@ -222,11 +222,6 @@ static int sdhci_at91_set_clks_presets(struct device *dev)
> >>> preset_div = DIV_ROUND_UP(gck_rate, 50000000) - 1;
> >>> writew(SDHCI_AT91_PRESET_COMMON_CONF | preset_div,
> >>> host->ioaddr + SDHCI_PRESET_FOR_DDR50);
> >>> -
> >>> - clk_prepare_enable(priv->mainck);
> >>> - clk_prepare_enable(priv->gck);
> >>> -
> >>> - return 0;
> >>> }
> >>>
> >>> static int sdhci_at91_suspend(struct device *dev)
> >>> @@ -254,9 +249,11 @@ 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->keep_clks_on) {
> >>> + clk_disable_unprepare(priv->gck);
> >>> + clk_disable_unprepare(priv->hclock);
> >>> + clk_disable_unprepare(priv->mainck);
> >>> + }
> >>>
> >>> return 0;
> >>> }
> >>> @@ -269,14 +266,23 @@ static int sdhci_at91_runtime_resume(struct device *dev)
> >>> int ret;
> >>>
> >>> if (priv->restore_needed) {
> >>> - ret = sdhci_at91_set_clks_presets(dev);
> >>> - if (ret)
> >>> - return ret;
> >>> + if (!priv->soc_data->keep_clks_on)
> >>> + clk_prepare_enable(priv->hclock);
> >>> +
> >>> + sdhci_at91_set_clks_presets(dev);
> >>> +
> >>> + if (!priv->soc_data->keep_clks_on) {
> >>> + clk_prepare_enable(priv->mainck);
> >>> + clk_prepare_enable(priv->gck);
> >>> + }
> >>>
> >>> priv->restore_needed = false;
> >>> goto out;
> >>> }
> >>>
> >>> + if (priv->soc_data->keep_clks_on)
> >>> + goto out;
> >>> +
> >>> ret = clk_prepare_enable(priv->mainck);
> >>> if (ret) {
> >>> dev_err(dev, "can't enable mainck\n");
> >>> @@ -344,9 +350,10 @@ 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);
> >>> - if (ret)
> >>> - return ret;
> >>> + clk_prepare_enable(priv->hclock);
> >>> + sdhci_at91_set_clks_presets(&pdev->dev);
> >>> + clk_prepare_enable(priv->mainck);
> >>> + clk_prepare_enable(priv->gck);
> >>>
> >>> priv->restore_needed = false;
> >>>
> >>> --
> >>> 2.55.0
> >>
> >
> >
> > --
> > Robert Marko
> > Staff Embedded Linux Engineer
> > Sartura d.d.
> > Lendavska ulica 16a
> > 10000 Zagreb, Croatia
> > Email: robert.marko at sartura.hr
> > Web: www.sartura.hr
>
--
Robert Marko
Staff Embedded Linux Engineer
Sartura d.d.
Lendavska ulica 16a
10000 Zagreb, Croatia
Email: robert.marko at sartura.hr
Web: www.sartura.hr
More information about the linux-arm-kernel
mailing list