netdev - Re: [PATCH net-next 25/28] [RFC] net: dpaa: Convert to phylink

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Date:   Sat, 18 Jun 2022 09:22:05 +0100
From:   "Russell King (Oracle)" <linux@...linux.org.uk>
To:     Sean Anderson <sean.anderson@...o.com>
Cc:     "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Madalin Bucur <madalin.bucur@....com>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        Paolo Abeni <pabeni@...hat.com>,
        Eric Dumazet <edumazet@...gle.com>
Subject: Re: [PATCH net-next 25/28] [RFC] net: dpaa: Convert to phylink

On Fri, Jun 17, 2022 at 08:45:38PM -0400, Sean Anderson wrote:
> Hi Russell,
> 
> Thanks for the quick response.
>...
> Yes, I've been using the debug prints in phylink extensively as part of
> debugging :)
> 
> In this case, I added a debug statement to phylink_resolve printing out
> cur_link_state, link_state.link, and pl->phy_state.link. I could see that
> the phy link state was up and the mac (pcs) state was down. By inspecting
> the PCS's registers, I determined that this was because AN had not completed
> (in particular, the link was up in BMSR). I believe that forcing in-band-status
> (by setting ovr_an_inband) shouldn't be necessary, but I was unable to get a link
> up on any interface without it. In particular, the pre-phylink implementation
> disabled PCS AN only for fixed links (which you can see in patch 23).

I notice that prior to patch 23, the advertisment register was set to
0x4001, but in phylink_mii_c22_pcs_encode_advertisement() we set it to
0x0001 (bit 14 being the acknowledge bit from the PCS to the PHY, which
is normally managed by hardware.

It may be worth testing whether setting bit 14 changes the behaviour.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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