On Tue, Aug 08, 2023 at 02:16:50PM +0200, Bartosz Golaszewski wrote:
> On Tue, Aug 8, 2023 at 12:27 AM Andrew Halaney <ahalaney@xxxxxxxxxx> wrote:
> >
> > On Mon, Aug 07, 2023 at 11:51:40PM +0200, Andrew Lunn wrote:
> > > > > I have proposed a solution for this problem in 2020 but it never got
> > > > > upstream. Now we have a workaround in place which allows us to hard-code
> > > > > the PHY id in the compatible property, thus skipping the ID scanning).
> > > >
> > > > nitpicky, but I think that already existed at that time :D
> > >
> > > Yes, it has been there are long long time. It is however only in the
> > > last 5 years of so has it been seen as a solution to the chicken egg
> > > problem.
> > >
> > > > > sgmii_phy: phy@8 {
> > > > > + compatible = "ethernet-phy-id0141.0dd4";
> > > > > reg = <0x8>;
> > > > > device_type = "ethernet-phy";
> > > > > + reset-gpios = <&pmm8654au_2_gpios 8 GPIO_ACTIVE_LOW>;
> > > > > + reset-deassert-us = <70000>;
> > > >
> > > > Doesn't this need reset-assert-us?
> > >
> > > If i remember correctly, there is a default value if DT does not
> > > provide one.
> > >
> >
> > I've been trying to make sure I view devicetree properties as an OS
> > agnostic ABI lately, with that in mind...
> >
> > The dt-binding says this for ethernet-phy:
> >
> > reset-assert-us:
> > description:
> > Delay after the reset was asserted in microseconds. If this
> > property is missing the delay will be skipped.
> >
> > If the hardware needs a delay I think we should encode it based on that
> > description, else we risk it starting to look like a unit impulse!
> >
>
> Please note that the mdio-level delay properties are not the same as
> the ones on the PHY levels.
>
> reset-delay-us - this is the delay BEFORE *DEASSERTING* the reset line
> reset-post-delay-us - this is the delay AFTER *DEASSERTING* the reset line
>
> On PHY level we have:
>
> reset-assert-us - AFTER *ASSERTING*
> reset-deassert-us - AFTER *DEASSERTING*
>
> There never has been any reset-assert delay on that line before. It
> doesn't look like we need a delay BEFORE deasserting the line, do we?
>
The MDIO reset-delay-us happens "before deassert"/"after assert", so to
make things a proper move here I think it needs a resrt-assert, otherwise
behavior with respect to reset timing is definitely changed from this
patch!
Here's a trimmed version of the reset handling in mdio_bus.c to back
that up:
/* assert bus level PHY GPIO reset */
gpiod = devm_gpiod_get_optional(&bus->dev, "reset", GPIOD_OUT_HIGH);
...
} else if (gpiod) {
bus->reset_gpiod = gpiod;
fsleep(bus->reset_delay_us);
gpiod_set_value_cansleep(gpiod, 0);
if (bus->reset_post_delay_us > 0)
fsleep(bus->reset_post_delay_us);
}
so its assert reset, sleep reset_delay_us, deassert, sleep
reset_post_delay_us for the MDIO case.
Thanks,
Andrew
