netdev - Re: [PATCH v2] net: mtk_sgmii: implement mtk_pcs

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Date:   Mon, 16 Jan 2023 18:14:00 +0000
From:   "Russell King (Oracle)" <linux@...linux.org.uk>
To:     Bjørn Mork <bjorn@...k.no>
Cc:     Frank Wunderlich <frank-w@...lic-files.de>,
        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: [PATCH v2] net: mtk_sgmii: implement mtk_pcs_ops

On Mon, Jan 16, 2023 at 07:04:53PM +0100, Bjørn Mork wrote:
> Bjørn Mork <bjorn@...k.no> writes:
> 
> > [   52.473325] offset:20 0x10000
> 
> Should have warned about my inability to write the simplest code without
> adding more bugs than characters.  20 != 0x20

Ah, that kind of explains the lack of change in the values at offset 20!

> [   44.139420] mtk_soc_eth 15100000.ethernet wan: Link is Down
> [   47.259922] mtk_sgmii_select_pcs: id=1
> [   47.263683] mtk_pcs_config: interface=4
> [   47.267503] offset:0 0x140
> [   47.267505] offset:4 0x4d544950
> [   47.270210] offset:8 0x20
> [   47.273335] offset:0x20 0x31120018
> [   47.275939] forcing AN
> [   47.281676] mtk_pcs_config: rgc3=0x0, advertise=0x1 (changed), link_timer=1600000,  sgm_mode=0x103, bmcr=0x1200, use_an=1
> [   47.292610] mtk_pcs_link_up: interface=4
> [   47.296516] offset:0 0x81140
> [   47.296518] offset:4 0x4d544950
> [   47.299387] offset:8 0x1
> [   47.302512] offset:0x20 0x3112011b
> [   47.305043] mtk_soc_eth 15100000.ethernet wan: Link is Up - 1Gbps/Full - flow control rx/tx
> [   56.619420] mtk_soc_eth 15100000.ethernet wan: Link is Down
> [   60.779865] mtk_sgmii_select_pcs: id=1
> [   60.783623] mtk_pcs_config: interface=22
> [   60.787531] offset:0 0x81140
> [   60.787533] offset:4 0x4d544950
> [   60.790409] offset:8 0x1
> [   60.793535] offset:0x20 0x3112011b
> [   60.796057] mtk_pcs_config: rgc3=0x4, advertise=0x20 (changed), link_timer=10000000,  sgm_mode=0x0, bmcr=0x0, use_an=0
> [   60.810117] mtk_pcs_link_up: interface=22
> [   60.814110] offset:0 0x40140
> [   60.814112] offset:4 0x4d544950
> [   60.816976] offset:8 0x20
> [   60.820105] offset:0x20 0x31120018
> [   60.822723] mtk_soc_eth 15100000.ethernet wan: Link is Up - 2.5Gbps/Full - flow control rx/tx

That all looks fine. However, I'm running out of ideas. What we
seem to have is:

PHY:
VSPEC1_SGMII_CTRL = 0x34da
VSPEC1_SGMII_STAT = 0x000e

The PHY is programmed to exchange SGMII with the host PCS, and it
says that it hasn't completed that exchange (bit 5 of STAT).

The Mediatek PCS says:
BMCR = 0x1140		AN enabled
BMSR = 0x0008		AN capable
ADVERTISE = 0x0001	SGMII response (bit 14 is clear, hardware is
			supposed to manage that bit)
LPA = 0x0000		SGMII received control word (nothing)
SGMII_MODE = 0x011b	SGMII mode, duplex AN, 1000M, Full duplex,
			Remote fault disable

which all looks like it should work - but it isn't.

One last thing I can think of trying at the moment would be writing
the VSPEC1_SGMII_CTRL with 0x36da, setting bit 9 which allegedly
restarts the SGMII exchange. There's some comments in the PHY driver
that this may be needed - maybe it's necessary once the MAC's PCS
has been switched to SGMII mode.

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