Re: [PATCH v4.1] phylib: Add device reset GPIO support

[Sergei Shtylyov]

On 12/07/2017 08:20 PM, Sergei Shtylyov wrote:

> > 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@xxxxxxxxxxxxxxxxxx>
> > Acked-by: Rob Herring <robh@xxxxxxxxxx>
> > [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@xxxxxxxxx>
> [...]
> > 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?

   Oops, error means we couldn't drive the GPIO at all...
   The 1st question remains though...

[...]

MBR, Sergei