Re: [PATCH 2/2] net: phy: marvell-88q2xxx: Prevent reading temperature with asserted reset

From: Stefan Eichenberger
Date: Wed Feb 19 2025 - 01:30:08 EST


Hi Dimitri,

On Tue, Feb 18, 2025 at 07:33:10PM +0100, Dimitri Fedrau wrote:
> If the PHYs reset is asserted it returns 0xffff for any read operation.
> Prevent reading the temperature in this case and return with an I/O error.
> Write operations are ignored by the device.
>
> Fixes: a197004cf3c2 ("net: phy: marvell-88q2xxx: Fix temperature measurement with reset-gpios")
> Signed-off-by: Dimitri Fedrau <dima.fedrau@xxxxxxxxx>
> ---
> drivers/net/phy/marvell-88q2xxx.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/drivers/net/phy/marvell-88q2xxx.c b/drivers/net/phy/marvell-88q2xxx.c
> index 30d71bfc365597d77c34c48f05390db9d63c4af4..c1ae27057ee34feacb31c2e3c40b2b1769596408 100644
> --- a/drivers/net/phy/marvell-88q2xxx.c
> +++ b/drivers/net/phy/marvell-88q2xxx.c
> @@ -647,6 +647,12 @@ static int mv88q2xxx_hwmon_read(struct device *dev,
> struct phy_device *phydev = dev_get_drvdata(dev);
> int ret;
>
> + /* If the PHYs reset is asserted it returns 0xffff for any read
> + * operation. Return with an I/O error in this case.
> + */
> + if (phydev->mdio.reset_state == 1)
> + return -EIO;
> +
> switch (attr) {
> case hwmon_temp_input:
> ret = phy_read_mmd(phydev, MDIO_MMD_PCS,
>

It makes sense to me. However, aren't most phys that allow reading
sensors over MDIO affected by this issue? I couldn't find anything
similar, are they ignoring that use-case?

Regards,
Stefan