netdev - Re: [PATCH] net: mvpp2: add delay at the end of .mac

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Message-ID: <CAPv3WKc1eM4gyD_VG2M+ozzvLYrDAXiKGvK6Ej_ykRVf-Zf9Mw@mail.gmail.com>
Date:   Thu, 28 Apr 2022 18:38:26 +0200
From:   Marcin Wojtas <mw@...ihalf.com>
To:     Baruch Siach <baruch@...s.co.il>
Cc:     Russell King <linux@...linux.org.uk>,
        netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH] net: mvpp2: add delay at the end of .mac_prepare

Hi Baruch,

czw., 28 kwi 2022 o 13:16 Baruch Siach <baruch@...s.co.il> napisał(a):
>
> Hi Marcin,
>
> On Thu, Apr 28 2022, Marcin Wojtas wrote:
> > śr., 27 kwi 2022 o 17:05 Baruch Siach <baruch@...s.co.il> napisał(a):
> >>
> >> From: Baruch Siach <baruch.siach@...lu.com>
> >>
> >> Without this delay PHY mode switch from XLG to SGMII fails in a weird
> >> way. Rx side works. However, Tx appears to work as far as the MAC is
> >> concerned, but packets don't show up on the wire.
> >>
> >> Tested with Marvell 10G 88X3310 PHY.
> >>
> >> Signed-off-by: Baruch Siach <baruch.siach@...lu.com>
> >> ---
> >>
> >> Not sure this is the right fix. Let me know if you have any better
> >> suggestion for me to test.
> >>
> >> The same issue and fix reproduce with both v5.18-rc4 and v5.10.110.
> >> ---
> >>  drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c | 2 ++
> >>  1 file changed, 2 insertions(+)
> >>
> >> diff --git a/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c b/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
> >>n index 1a835b48791b..8823efe396b1 100644
> >> --- a/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
> >> +++ b/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
> >> @@ -6432,6 +6432,8 @@ static int mvpp2_mac_prepare(struct phylink_config *config, unsigned int mode,
> >>                 }
> >>         }
> >>
> >> +       mdelay(10);
> >> +
> >>         return 0;
> >>  }
> >
> > Thank you for the patch and debug effort, however at first glance it
> > seems that adding delay may be a work-around and cover an actual root
> > cause (maybe Russell will have more input here).
>
> That's my suspicion as well.
>
> > Can you share exact reproduction steps?
>
> I think I covered all relevant details. Is there anything you find
> missing?
>
> The hardware setup is very similar to the Macchiatobin Doubleshot. I can
> try to reproduce on that platform next week if it helps.
>
> The PHY MAC type (MV_V2_33X0_PORT_CTRL_MACTYPE_MASK) is set to
> MV_V2_33X0_PORT_CTRL_MACTYPE_10GBASER.
>
> I can add that DT phy-mode is set to "10gbase-kr" (equivalent to
> "10gbase-r" in this case). The port cp0_eth0 is connected to a 1G
> Ethernet switch. Kernel messages indicate that on interface up the MAC
> is first configured to XLG (10G), but after Ethernet (wire)
> auto-negotiation that MAC switches to SGMII. If I set DT phy-mode to
> "sgmii" the issue does not show. Same if I make a down/up cycle of the
> interface.
>
> Thanks for your review.
>

I booted MacchiatoBin doubleshot with DT (phy-mode set to "10gbase-r")
without your patch and the 3310 PHY is connected to 1G e1000 card.
After `ifconfig eth0 up` it properly drops to SGMII without any issue
in my setup:

# ifconfig eth0 up
[   62.006580] mvpp2 f2000000.ethernet eth0: PHY
[f212a600.mdio-mii:00] driver [mv88x3310] (irq=POLL)
[   62.016777] mvpp2 f2000000.ethernet eth0: configuring for phy/sgmii link mode
# [   66.110289] mvpp2 f2000000.ethernet eth0: Link is Up - 1Gbps/Full
- flow control rx/tx
[   66.118270] IPv6: ADDRCONF(NETDEV_CHANGE): eth0: link becomes ready
# ifconfig eth0 192.168.1.1
# ping 192.168.1.2
PING 192.168.1.2 (192.168.1.2): 56 data bytes
64 bytes from 192.168.1.2: seq=0 ttl=64 time=0.511 ms
64 bytes from 192.168.1.2: seq=1 ttl=64 time=0.212 ms

Are you aware of the firmware version of the 3310 PHY in your setup?
In my case it's:
mv88x3310 f212a600.mdio-mii:00: Firmware version 0.3.3.0

Best regards,
Marcin