# Re: \[PATCH v3 1/4\] phylib: Add device reset GPIO support

- From: Sergei Shtylyov \<hidden\>
- Date: 2017-10-20 10:56:10 
- List: netdev
- Page: https://ratatoskr.run/netdev/2017/10/5114800
- Thread: https://ratatoskr.run/netdev/2017/10/5114667/t.md

```text
Hello!

On 10/20/2017 11:14 AM, Geert Uytterhoeven wrote:

> From: Sergei Shtylyov <redacted>
>
> The PHY devices sometimes do have their reset signal (maybe even power
> supply?) tied to some GPIO and sometimes it also does happen that a boot
> loader does not leave it deasserted. So far this issue has been attacked
> from (as I believe) a wrong angle: by teaching the MAC driver to manipulate
> the GPIO in question; that solution, when applied to the device trees, led
> to adding the PHY reset GPIO properties to the MAC device node, with one
> exception: Cadence MACB driver which could handle the "reset-gpios" prop
> in a PHY device subnode. I believe that the correct approach is to teach
> the 'phylib' to get the MDIO device reset GPIO from the device tree node
> corresponding to this device -- which this patch is doing...
>
> Note that I had to modify the AT803x PHY driver as it would stop working
> otherwise -- it made use of the reset GPIO for its own purposes...
>
> Signed-off-by: Sergei Shtylyov <redacted>
> Acked-by: Rob Herring <robh@kernel.org>
> Acked-by: Florian Fainelli <f.fainelli@gmail.com>
> [geert: Propagate actual errors from fwnode_get_named_gpiod()]
> Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
[...]
> diff --git a/drivers/net/phy/mdio_device.c b/drivers/net/phy/mdio_device.c
> index e24f28924af8953d..6926db11ae888174 100644
> --- a/drivers/net/phy/mdio_device.c
> +++ b/drivers/net/phy/mdio_device.c
[...]
> @@ -128,9 +136,16 @@ static int mdio_probe(struct device *dev)
>   	struct mdio_driver *mdiodrv = to_mdio_driver(drv);
>   	int err = 0;
>   
> -	if (mdiodrv->probe)
> +	if (mdiodrv->probe) {
> +		/* Deassert the reset signal */
> +		mdio_device_reset(mdiodev, 0);
> +
>   		err = mdiodrv->probe(mdiodev);

   If the probe() method performs some register setup...

> +		/* Assert the reset signal */
> +		mdio_device_reset(mdiodev, 1);

   ... this reset would kill that setup. Hence we shouldn't drive the reset signal at least when the probe() method succeeds.

> +	}
> +
>   	return err;
>   }
>   
[...]
> diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
> index 67f25ac29025c539..e694b0ecf780d096 100644
> --- a/drivers/net/phy/phy_device.c
> +++ b/drivers/net/phy/phy_device.c
[...]
> @@ -1811,9 +1826,16 @@ static int phy_probe(struct device *dev)
>   	/* Set the state to READY by default */
>   	phydev->state = PHY_READY;
>   
> -	if (phydev->drv->probe)
> +	if (phydev->drv->probe) {
> +		/* Deassert the reset signal */
> +		phy_device_reset(phydev, 0);
> +
>   		err = phydev->drv->probe(phydev);

   If the probe() method performs some register setup (as does the LXT PHY driver!)...

> +		/* Assert the reset signal */
> +		phy_device_reset(phydev, 1);

   ... this reset would kill that setup. Hence we shouldn't drive the reset signal at least when the probe() method succeeds.

> +	}
> +
>   	mutex_unlock(&phydev->lock);
>   
>   	return err;
[...]

MBR, Sergei
```