netdev - Re: No traffic with Marvell switch and latest linux-next

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Date:   Sat, 23 Feb 2019 15:55:46 -0800
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Heiner Kallweit <hkallweit1@...il.com>,
        Andrew Lunn <andrew@...n.ch>
Cc:     Russell King - ARM Linux admin <linux@...linux.org.uk>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: No traffic with Marvell switch and latest linux-next

Le 2/23/19 à 1:48 PM, Heiner Kallweit a écrit :
> On 18.02.2019 19:21, Andrew Lunn wrote:
>>>> Hi Heiner
>>>>
>>>> Watch out for boot vs reboot, and when rebooting if port 8 had link or
>>>> not before you reboot.
>>>>
>>> Will do. Is there some known issue or bug?
>>
>> Hi Heiner
>>
>> No, but it is a variable which can make a difference. The fix i made
>> for the Freescale GPIO controller was not an issue for cold boot, but
>> reboot with link up did cause interrupt problems, etc.
>>
> Hi Andrew,
> 
> it took me quite some time to debug this issue ..
> 
> At first a bisect pointed to one of my commits:
> 5502b218e001 ("net: phy: use phy_resolve_aneg_linkmode in genphy_read_status")

This is the same issue that Michal reported here:

https://www.spinics.net/lists/netdev/msg552955.html

> 
> Further digging lead me to some suspicious dsa code:
> In dsa_port_fixed_link_register_of() there's a call to genphy_read_status().
> At the time of the call phydev->advertising is empty, therefore the fixed phy
> settings are overwritten with defaults (10/half) what breaks the system.
> 
> Worth to be mentioned is that for the PHY these two flags are set:
> - is_pseudo_fixed_link (that's ok)
> - autoneg -> I'm not sure this is correct.
> 
> It seems that you once added the code in question:
> 39b0c705195e ("net: dsa: Allow configuration of CPU & DSA port speeds/duplex")
> 
> I did what I like to do most and removed some code.
> W/o the calls to genphy_config_init() and genphy_read_status() it works again.
> Do these calls have some purpose here with a fixed link?
> 
> My commit exposed the issue because before it genphy_read_status() read the
> advertisement from chip registers instead of using phydev->advertising.
> 
> Very close to this function is dsa_port_setup_phy_of() which uses genphy_resume()
> and genphy_read_status() and also looks somewhat suspicious. This code makes
> quite some assumptions:
> - PHY is a C22 PHY
> - PHY is compatible with the generic PHY driver
> 
>>        Andrew
>>
> Heiner
> 


-- 
Florian