Re: [PATCH net-next v5 02/19] net: stmmac: request the MDIO reset GPIO only once

[Linus Walleij]

Hi James,

On Sun, Sep 27, 2026 at 11:59 PM James Hilliard
<james.hilliard1@xxxxxxxxx> wrote:

> From: Linkui Xiao <xiaolinkui@xxxxxxxxxx>
>
> stmmac_mdio_reset() calls devm_gpiod_get_optional() every time it runs.
> A GPIO line can only be requested once, so from the second call on
> gpiod_request_commit() returns -EBUSY. devm_gpiod_get_optional() only
> turns -ENOENT into NULL, hence the error is passed straight back and
> stmmac_mdio_reset() bails out before pulsing "snps,reset" and before
> running the STE101P MDC workaround.
>
> The first call, made by of_mdiobus_register(), succeeds, so the failure
> is only visible later on: every resume that does not use WoL goes
> through stmmac_resume() -> stmmac_mdio_reset(), and that caller ignores
> the return value, so the PHY silently stays un-reset.
>
> The descriptor used to be requested exactly once: stmmac_mdio_reset()
> resolved "snps,reset-gpio" itself and cached the GPIO number in
> stmmac_mdio_bus_data::reset_gpio, and commit ae26c1c6cb9b ("stmmac: fix
> PHY reset during resume") relies on that cache to reuse the line on
> every call. commit 7c86f20d15b7 ("net: stmmac: use GPIO descriptors in
> stmmac_mdio_reset") replaced it with a devm_gpiod_get_optional() that
> caches nothing, so the request is repeated on every call and fails from
> the second one on.
>
> Parse the whole reset description, the GPIO and "snps,reset-delays-us",
> in stmmac_mdio_register() at probe time, and keep it in struct
> stmmac_priv. This is where devm-gpiod is meant to be used: the line is
> acquired with the device and released with it, and any failure to
> acquire it is reported during probe instead of being ignored by
> stmmac_resume(). stmmac_mdio_reset() then only pulses the cached line,
> with the delays that were read once and for all at probe time.
>
> Cache the request and delays for DT devices regardless of
> mdio_bus_data->needs_reset. That flag controls the registration-time
> bus reset callback, but system resume calls stmmac_mdio_reset()
> directly. The reset routine no longer looks at the device tree: where
> the description is absent the cached descriptor is NULL and the delays
> are zero, so the pulse remains a no-op.
>
> Keep acquisition conditional on CONFIG_STMMAC_PLATFORM, matching the
> reset callback, so non-platform configurations do not request an unused
> GPIO. Also skip acquisition for a disabled MDIO child: registering that
> bus returns -ENODEV without calling its reset callback, and the driver
> must retain the existing disabled-bus success path even if the unused
> GPIO is unavailable. Remove the unnecessary gpio_desc forward declaration.
>
> Fixes: 7c86f20d15b7 ("net: stmmac: use GPIO descriptors in stmmac_mdio_reset")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Linkui Xiao <xiaolinkui@xxxxxxxxxx>
> Co-developed-by: James Hilliard <james.hilliard1@xxxxxxxxx>
> Signed-off-by: James Hilliard <james.hilliard1@xxxxxxxxx>

Dostoyevsky commit message, I didn't read it. Ask the agent
to be terse.

I looked at the code and from a GPIO PoV it does the right
thing: use 1 as asserted and 0 as de-asserted RESET line.

Reviewed-by: Linus Walleij <linusw@xxxxxxxxxx>

Yours,
Linus Walleij