Re: [PATCH v3 net-next] net: phy: realtek: read actual speed on rtl8211f to detect downshift

[Yonglong Liu]

Hi, Russell:

    I found this message in kernel log, thanks!

On 2020/11/26 1:07, Russell King - ARM Linux admin wrote:
> On Thu, Nov 26, 2020 at 12:57:37AM +0800, Yonglong Liu wrote:
> > Hi, Antonio:
> >
> >      Could you help to provide a downshift warning message when this happen?
> >
> >      It's a little strange that the adv and the lpa support 1000M, but
> > finally the link speed is 100M.
> That is an identifying feature of downshift.
>
> Downshift can happen at either end of the link, and since we must not
> change the "Advertised link modes" since this is what userspace
> configured, if a downshift occurs at the local end, then you will get
> the ethtool output you provide, where the speed does not agree with
> the reported advertisements.
>
> You should already be getting a warning in the kernel log when this
> happens; phy_check_downshift() which is part of the phylib core code
> will check this every time the link comes up. You should already
> have a message "Downshift occurred ..." in your kernel log. Please
> check.