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

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

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.

> 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.

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.

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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>>
> 
> 

-- 
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