netdev - Re: [PATCH net-next v4 RESEND] stmmac: tegra: Add MGBE support

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Date:   Fri, 18 Nov 2022 15:02:16 +0200
From:   Vladimir Oltean <olteanv@...il.com>
To:     Bhadram Varka <vbhadram@...dia.com>
Cc:     Florian Fainelli <f.fainelli@...il.com>,
        Thierry Reding <thierry.reding@...il.com>,
        "David S . Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Russell King <linux@...linux.org.uk>,
        Andrew Lunn <andrew@...n.ch>,
        Revanth Kumar Uppala <ruppala@...dia.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        "linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next v4 RESEND] stmmac: tegra: Add MGBE support

Hi Bhadram,

On Wed, Oct 12, 2022 at 04:56:52AM +0000, Bhadram Varka wrote:
> > You should be modeling this as a proper PCS driver and have a 'pcs-handle'
> > property pointing to it in your Device Tree.
> > 
> > The configuration you are doing here is probably working the first time you
> > bring-up the network device but I doubt it works across system
> > suspend/resume states where power to the GMAC and PCS is lost, it also
> > begs the question of which mediums this was tested with and whether
> > dynamic switching of speeds and so on is working?
> > --
> 
> For Tegra234, there is UPHY lanes control logic inside XPCS IP which is memory-mapped IP (not part of the MAC IP).
> mgbe_uphy_lane_bringup performs UPHY lane bring up here. Here MGBE/XPCS works in XFI mode.
> 
> Agree that lane bring down logic is not present interface down/suspend paths. Will update the changes accordingly.
> One more thing is that UPHY lane bring should happen only after the line side link is up. This also will make the changes.
> Please let me know if I miss anything here.

What about the non-UPHY part of the XPCS IP, how does the dwmac-tegra.c
driver control it/see the status it reports?