Re: [PATCH] mmc: pwrseq_simple: fix probe failure when CONFIG_RESET_GPIO is enabled

[Ulf Hansson]

+ gpio and reset maintainers

On Fri, 20 Feb 2026 at 20:47, Sergey Suloev <sergey.suloev@xxxxxxxxx> wrote:
>
> The driver uses a heuristic — checking if exactly one entry exists in
> 'reset-gpios' — to decide whether to attempt reset controller API usage
> via devm_reset_control_get_optional_shared(). This is semantically
> incorrect and causes a permanent probe failure when CONFIG_RESET_GPIO
> is enabled.
>
> When CONFIG_RESET_GPIO=y, __of_reset_control_get() intercepts the
> 'reset-gpios' DT property and attempts to register the GPIO as a reset
> controller via __reset_add_reset_gpio_device(). If the GPIO controller
> is not yet fully initialized at probe time, this returns -ENOENT instead
> of -EPROBE_DEFER, and the error path does not respect the 'optional'
> flag, causing pwrseq_simple to fail permanently rather than defer.
> This prevents mmc1 from probing on boards that use 'reset-gpios' for
> WiFi power sequencing, such as BananaPi M2 Magic with AP6212/BCM43430
> on Allwinner R16.
>
> The correct indicator of reset controller intent is the explicit presence
> of a 'resets' property in the device tree node, not the count of
> 'reset-gpios' entries. A single 'reset-gpios' entry is just as likely
> to be a plain GPIO as multiple entries.
>
> Replace the ngpio == 1 heuristic with an explicit check for the 'resets'
> DT property, making the behavior unambiguous and immune to
> CONFIG_RESET_GPIO interference.
>
> Fixes: 73bf4b7381f7 ("mmc: pwrseq_simple: add support for one reset control")
> Signed-off-by: Sergey Suloev <sergey.suloev@xxxxxxxxx>
> ---
>  drivers/mmc/core/pwrseq_simple.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
>
> diff --git a/drivers/mmc/core/pwrseq_simple.c b/drivers/mmc/core/pwrseq_simple.c
> index 4b47e6c3b04b..780c8818a273 100644
> --- a/drivers/mmc/core/pwrseq_simple.c
> +++ b/drivers/mmc/core/pwrseq_simple.c
> @@ -124,7 +124,6 @@ static int mmc_pwrseq_simple_probe(struct platform_device *pdev)
>  {
>         struct mmc_pwrseq_simple *pwrseq;
>         struct device *dev = &pdev->dev;
> -       int ngpio;
>
>         pwrseq = devm_kzalloc(dev, sizeof(*pwrseq), GFP_KERNEL);
>         if (!pwrseq)
> @@ -134,8 +133,7 @@ static int mmc_pwrseq_simple_probe(struct platform_device *pdev)
>         if (IS_ERR(pwrseq->ext_clk) && PTR_ERR(pwrseq->ext_clk) != -ENOENT)
>                 return dev_err_probe(dev, PTR_ERR(pwrseq->ext_clk), "external clock not ready\n");
>
> -       ngpio = of_count_phandle_with_args(dev->of_node, "reset-gpios", "#gpio-cells");
> -       if (ngpio == 1) {
> +       if (device_property_present(dev, "resets")) {
>                 pwrseq->reset_ctrl = devm_reset_control_get_optional_shared(dev, NULL);
>                 if (IS_ERR(pwrseq->reset_ctrl))
>                         return dev_err_probe(dev, PTR_ERR(pwrseq->reset_ctrl),

Indeed the existing code looks a bit weird, but checking for the
"resets" property here should also require an update to the DT docs
[1].

I have looped in the gpio/reset maintainers to get their opinion on this too.

Kind regards
Uffe

[1] Documentation/devicetree/bindings/mmc/mmc-pwrseq-simple.yaml