linux-kernel - Re: Re: Re: [PATCH v2] net: mtk_sgmii: implement mtk_pcs

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Date:   Fri, 21 Oct 2022 22:28:09 +0100
From:   "Russell King (Oracle)" <linux@...linux.org.uk>
To:     Frank Wunderlich <frank-w@...lic-files.de>
Cc:     Frank Wunderlich <linux@...web.de>,
        linux-mediatek@...ts.infradead.org,
        Alexander Couzens <lynxis@...0.eu>,
        Felix Fietkau <nbd@....name>, John Crispin <john@...ozen.org>,
        Sean Wang <sean.wang@...iatek.com>,
        Mark Lee <Mark-MC.Lee@...iatek.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        netdev@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: Re: Re: [PATCH v2] net: mtk_sgmii: implement mtk_pcs_ops

On Fri, Oct 21, 2022 at 09:52:36PM +0200, Frank Wunderlich wrote:
> > Gesendet: Freitag, 21. Oktober 2022 um 20:31 Uhr
> > Von: "Russell King (Oracle)" <linux@...linux.org.uk>
> 
> > On Fri, Oct 21, 2022 at 07:47:47PM +0200, Frank Wunderlich wrote:
> > > > Gesendet: Freitag, 21. Oktober 2022 um 11:06 Uhr
> > > > Von: "Russell King (Oracle)" <linux@...linux.org.uk>
> 
> > > > Looking at SGMSYS_PCS_CONTROL_1, this is actually the standard BMCR in
> > > > the low 16 bits, and BMSR in the upper 16 bits, so:
> > > >
> > > > At address 4, I'd expect the PHYSID.
> > > > At address 8, I'd expect the advertisement register in the low 16 bits
> > > > and the link partner advertisement in the upper 16 bits.
> > > >
> > > > Can you try an experiment, and in mtk_sgmii_init() try accessing the
> > > > regmap at address 0, 4, and 8 and print their contents please?
> > >
> > > is this what you want to see?
> 
> > > [    1.083359] dev: 0 offset:0 0x840140
> > > [    1.083376] dev: 0 offset:4 0x4d544950
> > > [    1.086955] dev: 0 offset:8 0x1
> > > [    1.090697] dev: 1 offset:0 0x81140
> > > [    1.093866] dev: 1 offset:4 0x4d544950
> > > [    1.097342] dev: 1 offset:8 0x1
> >
> > Thanks. Decoding these...
> >
> > dev 0:
> >  BMCR: fixed, full duplex, 1000Mbps, !autoneg
> >  BMSR: link up
> >  Phy ID: 0x4d54 0x4950
> >  Advertise: 0x0001 (which would correspond with the MAC side of SGMII)
> >  Link partner: 0x0000 (no advertisement received, but we're not using
> >     negotiation.)
> >
> > dev 1:
> >  BMCR: autoneg (full duplex, 1000Mbps - both would be ignored)
> >  BMSR: able to do autoneg, no link
> >  Phy ID: 0x4d54 0x4950
> >  Advertise: 0x0001 (same as above)
> >  Link partner: 0x0000 (no advertisement received due to no link)
> >
> > Okay, what would now be interesting is to see how dev 1 behaves when
> > it has link with a 1000base-X link partner that is advertising
> > properly. If this changes to 0x01e0 or similar (in the high 16-bits
> > of offset 8) then we definitely know that this is an IEEE PHY register
> > set laid out in memory, and we can program the advertisement and read
> > the link partner's abilities.
> 
> added register-read on the the new get_state function too
> 
> on bootup it is now a bit different
> 
> [    1.086283] dev: 0 offset:0 0x40140 #was previously 0x840140
> [    1.086301] dev: 0 offset:4 0x4d544950
> [    1.089795] dev: 0 offset:8 0x1
> [    1.093584] dev: 1 offset:0 0x81140
> [    1.096716] dev: 1 offset:4 0x4d544950
> [    1.100191] dev: 1 offset:8 0x1
> 
> root@...-r3:~# ip link set eth1 up
> [  172.037519] mtk_soc_eth 15100000.ethernet eth1: configuring for inband/1000base-x link mode
> root@...-r3:~#
> [  172.102949] offset:0 0x40140 #still same value

If this is "dev: 1" the value has changed - the ANENABLE bit has been
turned off, which means it's not going to bother receiving or sending
the 16-bit control word. Bit 12 needs to stay set for it to perform
the exchange.

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