netdev - Re: PHY VSC8531 MDIO data not reflected in ethernet/ sub-module

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Message-ID: <759ac0e2-9d5e-17ea-83e2-573a762492c2@mistywest.com>
Date: Thu, 11 May 2023 16:21:51 -0700
From: Ron Eggler <ron.eggler@...tywest.com>
To: Andrew Lunn <andrew@...n.ch>
Cc: netdev@...r.kernel.org
Subject: Re: PHY VSC8531 MDIO data not reflected in ethernet/ sub-module

Hi Andrew,

Thanks for your response:

On 2023-05-11 8:34 a.m., Andrew Lunn wrote:
>> ***[ 6.728165] DEBUG: in ravb_emac_init_gbeth(), calling
>> ravb_set_rate_gbeth(), priv->duplex: 0, priv->speed: 0*
>> ***[ 6.751973] DEBUG: in ravb_set_rate_gbeth() - priv->speed 0*
>> ***[ 6.831153] DEBUG: in ravb_adjust_link(), phydev->speed -1, priv->speed
>> 0*
>> ***[ 6.839952] DEBUG: in ravb_adjust_link(), priv->no_avb_link 0,
>> phydev->link 0*
> If there is no link, everything else is meaningless. You cannot have
> speed without link.
Makes sense!
>> While I also receive the following using the mii-tool utility:
>> # mii-tool -vv eth0
>> Using SIOCGMIIPHY=0x8947
>> eth0: negotiated 1000baseT-FD flow-control, link ok
>>    registers for MII PHY 0:
>>      1040 796d 0007 0572 01e1 cde1 000f 2001
>>      4006 0300 7800 0000 0000 4002 0000 3000
>>      0000 f000 0088 0000 0000 0001 3200 1000
>>      0000 0000 0000 0000 a035 0054 0400 0000
>>    product info: vendor 00:01:c1, model 23 rev 2
>>    basic mode:   autonegotiation enabled
>>    basic status: autonegotiation complete, link ok
>>    capabilities: 1000baseT-HD 1000baseT-FD 100baseTx-FD 100baseTx-HD
>> 10baseT-FD 10baseT-HD
>>    advertising:  1000baseT-FD 100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD
>>    link partner: 1000baseT-HD 1000baseT-FD 100baseTx-FD 100baseTx-HD
>> 10baseT-FD 10baseT-HD flow-control
> Assuming you are not using interrupts, phylib will poll the PHY once a
> second, calling
> phy_check_link_status()->

I don't see it being invoked every Seconds but it gets invoked on boot, 
I added debug logs and see the following:

[    6.669425] DEBUG: in phy_check_link_status(), phy_read_status() ret 
err 0, phydev->loopback_enabled 0,
[    6.696237] DEBUG: in phy_check_link_status(), phydev->link 0, 
phydev->state UP

state = UP which means it's ready to start auto negotiation(in 
phy_state_machine())  but instead in phy_check_link_status(), 
phydev->state should be set to  PHY_RUNNING but it only can get set to 
PHY_RUNNING when phydev->link is 1 (in phy_check_link_status()):

>    phy_read_status()->
>      phydev->drv->read_status()
> or
>      genphy_read_status()
>
> Check what these are doing, why do they think the link is down.

Yes, so in phy_read_status, phydev->drv->read_status appears to be set 
but I cannot figure out where it gets set. (I obviously need to find the 
function to find why the link isn't read correctly).
I temporarily set phydev->drv->read_status to 0 to force invocation of 
genphy_read_status() function to see how that would work.

genphy_update_link(0 is called from genphy_read_status() and I get the 
below data:

[    6.795480] DEBUG: in genphy_update_link(), after phy_read() bmcr 4160
[    6.805225] DEBUG: in genphy_update_link(), bmcr 0x1040 & 0x200
[    6.815730] DEBUG: in genphy_read_status(), genphy_update_link() 0 
phydev->autoneg 1, phydev->link 0


Could it be that the link needs a second to come up when when the 
network drivers get started and hence I should make sure that the 
polling once a second works (which currently doesn't appear to be the 
case)? Am I missing a configuration option?

Thanks!

-- 
Ron