[PATCH v3] net: phy: Support overriding Auto Negotiation timeout with env variable

[Siddharth Vadapalli]

On Wed, Jul 30, 2025 at 09:23:25AM +0200, Jerome Forissier wrote:

Hello Jerome,

> Hi Siddharth,
> 
> Replying since this patch has been standing in my queue (u-boot-net) and Tom
> asked me to give my opinion.
> 
> On 7/24/25 16:15, Siddharth Vadapalli wrote:
> > The Auto Negotiation procedure between two Ethernet PHYs consists of
> > determining the best commonly supported parameters among Speed,
> > Duplex Mode and Flow Control.
> > 
> > The time taken for this procedure is not only dependent on the local
> > PHY used, but also on the link-partner PHY.
> > 
> > While a timeout can be specified in the form of a "CONFIG" on the basis
> > of the local PHY present on the device, since the timeout also depends
> > on the link-partner PHY, it might be necessary to modify the timeout.
> > 
> > To avoid rebuilding the bootloader for a given device, just because it
> > may be connected to various link-partner PHYs, each with a different
> > timeout, introduce an environment variable named "phy_aneg_timeout" and
> > override "CONFIG_PHY_ANEG_TIMEOUT" with "phy_aneg_timeout".
> > 
> > Signed-off-by: Siddharth Vadapalli <s-vadapalli at ti.com>
> > ---
> 
> This looks sane to me. Based on a private email thread where various
> options were discussed, I think that:
> - Modifying the tree-wide default value for PHY_ANEG_TIMEOUT is probably
> not a good idea. Sure it is a timeout not a delay, so increasing it will
> go unnoticed for board that succeed the negotiation in less time. But it
> will have an impact on boot time if it is expected that one phy times
> out and another phy gets activated for example.
> - Making the default different for TI boards makes little sense. This is
> not an arch-specific thing.
> - Therfore, allowing the user to override the timeout via an env var for
> very specific deployment cases  seems like a good idea.

I agree with all of the statements above.

> 
> Acked-by: Jerome Forissier <jerome.forissier at linaro.org>

Thank you for reviewing the patch and sharing your thoughts, and also
for the acknowledgement tag.

Regards,
Siddharth.