Re: [PATCH v3 4/4] net: phy: at803x: add RX and TX clock management for IPQ5018 PHY

[Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>]

On 6/5/26 8:14 PM, Andrew Lunn wrote:
>>>> This PHY is integrated into the IPQ5018 SoC, connected to the first GMAC
>>>> (GMAC0) and probed upon boot. However, this PHY is not used on all
>>>> boards because an external PHY or switch can be wired to the SoC's
>>>> second GMAC instead (through a PCS). So from a power management
>>>> perspective, it would be better if we can disable the clocks if there's
>>>> no link detected.
>>>
>>> Humm, is link the correct criteria? If the PHY is not used,
>>> .config_aneg should not be called. Why not have the probe method get
>>> the optional clocks, but leave them off. When .config_aneg is called
>>> for the first time, enable the clocks?
>>
>> Will check if config_aneg is called and test accordingly.
>>
>> ip link set eth0 up/down and cable (un)plug do trigger
>> link_change_notify, and based on the link state the RX/TX clocks are
>> turned off/on properly.
> 
> You are talking about something else here. You say the device is not
> used. If it is not used, .config_aneg should not be called.
> 
> This is a second use case, the device is used, and you want to limit
> the power it consumes, when there is no link. Do you have any numbers?
> How much power is actually saved?

If the PHY is part of the SoC, keeping it online would require some
more hw to be online, so it probably sums up.. I don't know for sure,
I don't really work with the router SoCs

Is there any prior art wrt enabling/disabling the PHYs (not necessarily
clocks specifically, but say power supplies) at runtime?
A quick grep only points to this very driver, which gets the regulator
during probe, enables it and never turns it off

Maybe +Kathiravan knows more?

Konrad