netdev - Re: net: stmmac: dwmac-meson8b: interface sometimes does not come up at boot

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Date:   Wed, 9 Mar 2022 21:42:05 +0100
From:   Heiner Kallweit <hkallweit1@...il.com>
To:     Jerome Brunet <jbrunet@...libre.com>,
        Erico Nunes <nunes.erico@...il.com>
Cc:     Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        Giuseppe Cavallaro <peppe.cavallaro@...com>,
        Jose Abreu <joabreu@...opsys.com>,
        Kevin Hilman <khilman@...libre.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        linux-amlogic@...ts.infradead.org, netdev@...r.kernel.org,
        "open list:ARM/Rockchip SoC..." <linux-rockchip@...ts.infradead.org>,
        linux-sunxi@...ts.linux.dev
Subject: Re: net: stmmac: dwmac-meson8b: interface sometimes does not come up
 at boot

On 09.03.2022 15:57, Jerome Brunet wrote:
> 
> On Wed 09 Mar 2022 at 15:45, Erico Nunes <nunes.erico@...il.com> wrote:
> 
>> On Sun, Mar 6, 2022 at 1:56 PM Heiner Kallweit <hkallweit1@...il.com> wrote:
>>> You could try the following (quick and dirty) test patch that fully mimics
>>> the vendor driver as found here:
>>> https://github.com/khadas/linux/blob/buildroot-aml-4.9/drivers/amlogic/ethernet/phy/amlogic.c
>>>
>>> First apply
>>> https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net.git/commit/?id=a502a8f04097e038c3daa16c5202a9538116d563
>>> This patch is in the net tree currently and should show up in linux-next
>>> beginning of the week.
>>>
>>> On top please apply the following (it includes the test patch your working with).
>>
>> I triggered test jobs with this configuration (latest mainline +
>> a502a8f0409 + test patch for vendor driver behaviour), and the results
>> are pretty much the same as with the previous test patch from this
>> thread only.
>> That is, I never got the issue with non-functional link up anymore,
>> but I get the (rare) issue with link not going up.
>> The reproducibility is still extremely low, in the >1% range.
> 
> Low reproducibility means the problem is still there, or at least not
> understood completly.
> 
> I understand the benefit from the user standpoint.
> 
> Heiner if you are going to continue from the test patch you sent,
> I would welcome some explanation with each of the changes.
> 
The latest test patch was purely for checking whether we see any
difference in behavior between vendor driver and the mainlined
version. It's in no way meant to be applied to mainline.

> We know very little about this IP and I'm not very confortable with
> tweaking/aligning with AML sdk "blindly" on a driver that has otherwise
> been working well so far.
> 

This touches one thing I wanted to ask anyway: Supposedly Amlogic
didn't develop an own Ethernet PHY, and if they licensed an existing
IP then it should be similar to some other existing PHY (that may
have a driver in phylib).

Then what I'll do is submit the following small change that brought
the error rate significantly down according to Erico's tests.

-       phy_trigger_machine(phydev);
+       if (irq_status & INTSRC_ANEG_COMPLETE)
+               phy_queue_state_machine(phydev, msecs_to_jiffies(100));
+       else
+               phy_trigger_machine(phydev);


> Thx
> 
>>
>> So at this point, I'm not sure how much more effort to invest into
>> this. Given the rate is very low and the fallback is it will just
>> reset the link and proceed to work, I think the situation would
>> already be much better with the solution from that test patch being
>> merged. If you propose that as a patch separately, I'm happy to test
>> the final submitted patch again and provide feedback there. Or if
>> there is another solution to try, I can try with that too.
>>
>> Thanks
>>
>>
>> Erico
> 

Heiner