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SubjectRe: [PATCH v4.1] phylib: Add device reset GPIO support
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Hello!

On 12/04/2017 03:35 PM, Geert Uytterhoeven wrote:

> From: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
>
> 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 <sergei.shtylyov@cogentembedded.com>
> Acked-by: Rob Herring <robh@kernel.org>
> [geert: Propagate actual errors from fwnode_get_named_gpiod()]
> [geert: Avoid destroying initial setup]
> [geert: Consolidate GPIO descriptor acquiring code]
> Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
[...]
> diff --git a/drivers/net/phy/mdio_bus.c b/drivers/net/phy/mdio_bus.c
> index 2df7b62c1a36811e..8f8b7747c54bc478 100644
> --- a/drivers/net/phy/mdio_bus.c
> +++ b/drivers/net/phy/mdio_bus.c
[...]
> @@ -48,9 +49,26 @@
>
> int mdiobus_register_device(struct mdio_device *mdiodev)
> {
> + struct gpio_desc *gpiod = NULL;
> +
> if (mdiodev->bus->mdio_map[mdiodev->addr])
> return -EBUSY;
>
> + /* Deassert the optional reset signal */

Umm, but why deassert it here for such a short time?

> + if (mdiodev->dev.of_node)
> + gpiod = fwnode_get_named_gpiod(&mdiodev->dev.of_node->fwnode,
> + "reset-gpios", 0, GPIOD_OUT_LOW,
> + "PHY reset");
> + if (PTR_ERR(gpiod) == -ENOENT)
> + gpiod = NULL;
> + else if (IS_ERR(gpiod))
> + return PTR_ERR(gpiod);

Hm, returning on error with reset deasserted?

> +
> + mdiodev->reset = gpiod;
> +
> + /* Assert the reset signal again */
> + mdio_device_reset(mdiodev, 1);
> +
> mdiodev->bus->mdio_map[mdiodev->addr] = mdiodev;
>
> return 0;
[...]

MBR, Sergei

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