Re: [PATCH] ARM: dts: imx6ul-tx6ul: Switch away from deprecated `phy-reset-gpios`

[Buday Csaba <buday.csaba@prolan.hu>]

On Wed, Sep 03, 2025 at 10:43:46AM +0200, Ahmad Fatoum wrote:
> Hi,
> 
> On 9/3/25 10:01 AM, Buday Csaba wrote:
> > On Wed, Sep 03, 2025 at 09:50:08AM +0200, Ahmad Fatoum wrote:
> >>> [1] https://lore.kernel.org/lkml/20250709133222.48802-4-buday.csaba@prolan.hu/
> >>
> >> Is this mainline yet?
> >>
> > 
> > No, it is not. It was never the most beautiful piece of code, so I understand
> > that.
> > 
> > But if you could give us some guidance, that would help a lot.
> > 
> > Specifically:
> > 
> > 1)  If `phy-reset-gpios` is deprecated, than we should start treating it as
> >     such, and not rely on it in future releases. Perhaps we should also add a
> >     warning message, when it is found in the device tree.
> 
> Disagreed. Deprecated properties should be removed only about clarifying
> the impact of the removal on users. Replacing a deprecated property with
> an expectation that bootloader board code has deasserted reset is not
> acceptable IMO.

I was only trying to reason, that since `phy-reset-gpios` has been marked as 
deprecated in 5.3 (which was 6 years ago), perhaps a inserting a warning note
now would be appropriate.
But that is related to the driver, not the DT.
I completely agree with the rest.

> 
> > 2)  On the other hand, if it is here to stay for a long time, it should be
> >     fixed. Now the gpio is claimed during fec_reset_phy(), and never released.
> >     It can not be used by the driver later, like in fec_init(), because the
> >     gpio reference is only stored in a local variable of fec_reset_phy().
> >     Previous patches that would have stored the reference in the driver were
> >     rejected on the grounds that it is deprecated. But if it is not, then we
> >     can create a patch that would make it work properly.
> 
> Ye, this needs to be solved differently.
> 
> > 3)  Andrew pointed out, that resetting a PHY before probing it may cause
> >     regressions. That is certainly a valid concern, but for most of the 
> >     devices resetting it means starting from a known state, and should be the
> >     default. But we could create a device tree property, that controls this
> >     behaviour.
> 
> Marco had a more involved series to address this:
> https://lore.kernel.org/all/20230405-net-next-topic-net-phy-reset-v1-0-7e5329f08002@pengutronix.de/
> 
> But it went no where. I don't recall the details.
>

Interesting. So Andrew is not against resetting before probe, it just has to
be done properly. ;)
 
> I think the best you can do with existing bindings is to give your PHY a
> compatible that spells out vendor/device ID, e.g. ethernet-phy-id0141.0dd4.
> 
> Then Linux can probe the device even while it's in reset.
> 
> The downside is that it hardcodes a specific PHY ID, but this may be
> acceptable here.

Yes, for now that would be acceptable for us, with some loss of generality.

Regards,
Csaba

> 
> Cheers,
> Ahmad
> 
> > 
> > Regards,
> > Csaba
> > 
> >> Cheers,
> >> Ahmad
> >>
> >>>
> >>>>>
> >>>>> Co-developed-by: Csaba Buday <buday.csaba@prolan.hu>
> >>>>> Signed-off-by: Csaba Buday <buday.csaba@prolan.hu>lan8710 reset
> >>>>> Signed-off-by: Bence Csókás <csokas.bence@prolan.hu>
> >>>>> ---
> >>>>>   arch/arm/boot/dts/nxp/imx/imx6ul-tx6ul.dtsi | 8 +++++++-
> >>>>>   1 file changed, 7 insertions(+), 1 deletion(-)
> >>>>>
> >>>>> diff --git a/arch/arm/boot/dts/nxp/imx/imx6ul-tx6ul.dtsi b/arch/arm/boot/dts/nxp/imx/imx6ul-tx6ul.dtsi
> >>>>> index f053358bc9317f8447d65013a18670cb470106b2..0a5e90704ea481b0716d6ff6bc6d2110914d4f31 100644
> >>>>> --- a/arch/arm/boot/dts/nxp/imx/imx6ul-tx6ul.dtsi
> >>>>> +++ b/arch/arm/boot/dts/nxp/imx/imx6ul-tx6ul.dtsi
> >>>>> @@ -246,7 +246,6 @@ &fec1 {
> >>>>>       pinctrl-names = "default";
> >>>>>       pinctrl-0 = <&pinctrl_enet1 &pinctrl_enet1_mdio &pinctrl_etnphy0_rst>;
> >>>>>       phy-mode = "rmii";
> >>>>> -    phy-reset-gpios = <&gpio5 6 GPIO_ACTIVE_LOW>;
> >>>>>       phy-supply = <&reg_3v3_etn>;
> >>>>>       phy-handle = <&etnphy0>;
> >>>>>       status = "okay";
> >>>>> @@ -262,6 +261,13 @@ etnphy0: ethernet-phy@0 {
> >>>>>               pinctrl-0 = <&pinctrl_etnphy0_int>;
> >>>>>               interrupt-parent = <&gpio5>;
> >>>>>               interrupts = <5 IRQ_TYPE_EDGE_FALLING>;
> >>>>> +            /* Reset SHOULD be a PHY property */
> >>>>
> >>>> Comment belongs into commit message.
> >>>
> >>> Agreed.
> >>>
> >>>>> +            reset-names = "phy";
> >>>>> +            reset-gpios = <&gpio5 6 GPIO_ACTIVE_LOW>;
> >>>>> +            reset-assert-us = <100>;
> >>>>> +            reset-deassert-us = <25000>;
> >>>>> +            /* Energy detect sometimes causes link failures */
> >>>>> +            smsc,disable-energy-detect;
> >>>>
> >>>> Unrelated change not described in the commit message.
> >>>
> >>> Oh, this has accidentally made it into here from our DT. Thanks for spotting it!
> >>>
> >>>> Cheers,
> >>>> Ahmad
> >>>>
> >>>>>               status = "okay";
> >>>>>           };
> >>>>>  
> >>>>> ---
> >>>>> base-commit: 0cc53520e68bea7fb80fdc6bdf8d226d1b6a98d9
> >>>>> change-id: 20250815-b4-tx6ul-dt-phy-rst-7afc190a6907
> >>>>>
> >>>>> Best regards,
> >>>>
> >>>>
> >>>
> >>> Bence
> >>>
> >>>
> >>
> >>
> >> -- 
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> >>
> > 
> > 
> 
> -- 
> Pengutronix e.K.                  |                             |
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> 
>