On Wed, Dec 17, 2025 at 10:58:54AM +0100, Stefan Eichenberger wrote:

On Mon, Dec 15, 2025 at 08:03:30AM -0600, Rob Herring wrote:

quoted

On Fri, Dec 12, 2025 at 09:46:17AM +0100, Stefan Eichenberger wrote:

quoted

From: Stefan Eichenberger <redacted>

Add a property to activate a Micrel PHY feature that keeps the preamble
enabled before the SFD (Start Frame Delimiter) is transmitted.

This allows to workaround broken Ethernet controllers as found on the
NXP i.MX8MP. Specifically, errata ERR050694 that states:
ENET_QOS: MAC incorrectly discards the received packets when Preamble
Byte does not precede SFD or SMD.

It doesn't really work right if you have to change the DT to work-around 
a quirk in the kernel. You should have all the information needed 
already in the DT. The compatible string for the i.MX8MP ethernet 
controller is not sufficient? 

Is doing something like this acceptable in a phy driver?
if (of_machine_is_compatible("fsl,imx8mp")) {
...
}

That would be a different option, rather than having to add a new DT
property. Unfortunately, the workaround affects the PHY rather than the
MAC driver. This is why we considered adding a DT property.

Francesco made a good point about this. The i.MX8MP has two MACs, but
only one of them is affected. Therefore, checking the machine's
compatible string would not be correct. As far as I know, checking the
MAC's compatible string from within the PHY driver is also not good
practice, is it?