netdev - Re: [PATCH net] net: stmmac: work around sporadic tx issue on link-up

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Message-ID: <776ece87-e24c-bb19-e472-8a04d1cbbaa3@gmail.com>
Date:   Wed, 24 Aug 2022 22:36:27 +0200
From:   Heiner Kallweit <hkallweit1@...il.com>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     Giuseppe Cavallaro <peppe.cavallaro@...com>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        Jose Abreu <joabreu@...opsys.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "moderated list:ARM/STM32 ARCHITECTURE" 
        <linux-stm32@...md-mailman.stormreply.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        Qi Duan <qi.duan@...ogic.com>, Da Xue <da@...sconfused.com>,
        Jerome Brunet <jbrunet@...libre.com>
Subject: Re: [PATCH net] net: stmmac: work around sporadic tx issue on link-up

On 24.08.2022 01:22, Jakub Kicinski wrote:
> On Sat, 20 Aug 2022 17:20:37 +0200 Heiner Kallweit wrote:
>> This is a follow-up to the discussion in [0]. It seems to me that
>> at least the IP version used on Amlogic SoC's sometimes has a problem
>> if register MAC_CTRL_REG is written whilst the chip is still processing
>> a previous write. But that's just a guess.
>> Adding a delay between two writes to this register helps, but we can
>> also simply omit the offending second write. This patch uses the second
>> approach and is based on a suggestion from Qi Duan.
>> Benefit of this approach is that we can save few register writes, also
>> on not affected chip versions.
>>
>> This patch doesn't apply cleanly before the commit marked as fixed.
>> There's nothing wrong with this commit.
> 
> I don't think this is right, please do your best to identify where
> the bug was actually introduced and put that in the Fixes tag.
> 
> IIRC this is not the first time you've made this choice so let's
> sort this out, we can bring it up with Greg if you would like,
> I don't see it clarified in the docs.
> 
> My understanding and experience doing backports for my employer is 
> that cutting off the Fixes tag at the place patch application fails 
> is very counter productive. Better to go too far back and let 
> the person maintaining the tree decide if the backport is needed.
> 
OK, I changed the Fixes tag accordingly and submitted a v2.