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

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Message-ID: <Y8WSPjyz2TxyX3/R@shell.armlinux.org.uk>
Date:   Mon, 16 Jan 2023 18:06:54 +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 06:59:19PM +0100, Bjørn Mork wrote:
> "Russell King (Oracle)" <linux@...linux.org.uk> writes:
> 
> > On Mon, Jan 16, 2023 at 05:45:12PM +0100, Bjørn Mork wrote:
> >> Bjørn Mork <bjorn@...k.no> writes:
> >> 
> >> >> You have bmcr=0x1000, but the code sets two bits - SGMII_AN_RESTART and
> >> >> SGMII_AN_ENABLE which are bits 9 and 12, so bmcr should be 0x1200, not
> >> >> 0x1000. Any ideas why?
> >> >
> >> > No, not really
> >> 
> >> Doh! Looked over it again, and this was my fault of course.  Had an
> >> 
> >>   "bmcr = SGMII_AN_ENABLE;"
> >>   
> >> line overwriting the original value from a previous attempt without
> >> changing the if condition.. Thanks for spotting that.
> >> 
> >> But this still doesn't work any better:
> >> 
> >> [   43.019395] mtk_soc_eth 15100000.ethernet wan: Link is Down
> >> [   45.099898] mtk_sgmii_select_pcs: id=1
> >> [   45.103653] mtk_pcs_config: interface=4
> >> [   45.107473] offset:0 0x140
> >> [   45.107476] offset:4 0x4d544950
> >> [   45.110181] offset:8 0x20
> >> [   45.113305] forcing AN
> >> [   45.118256] mtk_pcs_config: rgc3=0x0, advertise=0x1 (changed), link_timer=1600000,  sgm_mode=0x103, bmcr=0x1200, use_an=1
> >> [   45.129191] mtk_pcs_link_up: interface=4
> >> [   45.133100] offset:0 0x81140
> >> [   45.133102] offset:4 0x4d544950
> >> [   45.135967] offset:8 0x1
> >> [   45.139104] mtk_soc_eth 15100000.ethernet wan: Link is Up - 1Gbps/Full - flow control rx/tx
> >
> > In your _dump_pcs_ctrl() function, please can you dump the
> > SGMSYS_SGMII_MODE register as well (offset 0x20), in case this gives
> > more clue as to what's going on.
> 
> 
> [   49.339410] mtk_soc_eth 15100000.ethernet wan: Link is Down
> [   52.459913] mtk_sgmii_select_pcs: id=1
> [   52.463673] mtk_pcs_config: interface=4
> [   52.467494] offset:0 0x140
> [   52.467496] offset:4 0x4d544950
> [   52.470199] offset:8 0x20
> [   52.473325] offset:20 0x10000
> [   52.475929] forcing AN
> [   52.481232] mtk_pcs_config: rgc3=0x0, advertise=0x1 (changed), link_timer=1600000,  sgm_mode=0x103, bmcr=0x1200, use_an=1
> [   52.492166] mtk_pcs_link_up: interface=4
> [   52.496072] offset:0 0x81140
> [   52.496074] offset:4 0x4d544950
> [   52.498938] offset:8 0x1
> [   52.502067] offset:20 0x10000
> [   52.504599] mtk_soc_eth 15100000.ethernet wan: Link is Up - 1Gbps/Full - flow control rx/tx
> [   65.979410] mtk_soc_eth 15100000.ethernet wan: Link is Down
> [   70.139856] mtk_sgmii_select_pcs: id=1
> [   70.143616] mtk_pcs_config: interface=22
> [   70.147523] offset:0 0x81140
> [   70.147525] offset:4 0x4d544950
> [   70.150402] offset:8 0x1
> [   70.153526] offset:20 0x10000
> [   70.156049] mtk_pcs_config: rgc3=0x4, advertise=0x20 (changed), link_timer=10000000,  sgm_mode=0x0, bmcr=0x0, use_an=0
> [   70.169672] mtk_pcs_link_up: interface=22
> [   70.173664] offset:0 0x40140
> [   70.173666] offset:4 0x4d544950
> [   70.176530] offset:8 0x20
> [   70.179659] offset:20 0x10000
> [   70.182279] mtk_soc_eth 15100000.ethernet wan: Link is Up - 2.5Gbps/Full - flow control rx/tx

Umm. What's at offset:20 seems to be unprogrammable - it always reads
back with only bit 16 set! This probably explains why it's not working,
as it looks like it can't be programmed to operate in SGMII mode!

-- 
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