linux-kernel - Re: [PATCH net 1/2] net: stmmac: fix dwmac1000 ptp timestamp status offset

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Message-Id: <D9DAS80VMYAW.3JALOQIHS2B0W@bootlin.com>
Date: Tue, 22 Apr 2025 18:11:18 +0200
From: Alexis Lothoré <alexis.lothore@...tlin.com>
To: "Maxime Chevallier" <maxime.chevallier@...tlin.com>
Cc: "Andrew Lunn" <andrew+netdev@...n.ch>, "David S. Miller"
 <davem@...emloft.net>, "Eric Dumazet" <edumazet@...gle.com>, "Jakub
 Kicinski" <kuba@...nel.org>, "Paolo Abeni" <pabeni@...hat.com>, "Maxime
 Coquelin" <mcoquelin.stm32@...il.com>, "Alexandre Torgue"
 <alexandre.torgue@...s.st.com>, "Richard Cochran"
 <richardcochran@...il.com>, "Daniel Machon" <daniel.machon@...rochip.com>,
 "Thomas Petazzoni" <thomas.petazzoni@...tlin.com>,
 <netdev@...r.kernel.org>, <linux-stm32@...md-mailman.stormreply.com>,
 <linux-arm-kernel@...ts.infradead.org>, <linux-kernel@...r.kernel.org>,
 "Russell King (Oracle)" <linux@...linux.org.uk>
Subject: Re: [PATCH net 1/2] net: stmmac: fix dwmac1000 ptp timestamp status
 offset

Hi Maxime,

On Tue Apr 22, 2025 at 5:49 PM CEST, Maxime Chevallier wrote:
> Hi Alexis,
>
> On Tue, 22 Apr 2025 17:07:22 +0200
> Alexis Lothore <alexis.lothore@...tlin.com> wrote:
>
>> When a PTP interrupt occurs, the driver accesses the wrong offset to
>> learn about the number of available snapshots in the FIFO for dwmac1000:
>> it should be accessing bits 29..25, while it is currently reading bits
>> 19..16 (those are bits about the auxiliary triggers which have generated
>> the timestamps). As a consequence, it does not compute correctly the
>> number of available snapshots, and so possibly do not generate the
>> corresponding clock events if the bogus value ends up being 0.
>> 
>> Fix clock events generation by reading the correct bits in the timestamp
>> register for dwmac1000.
>> 
>> Fixes: 19b93bbb20eb ("net: stmmac: Introduce dwmac1000 timestamping operations")
>
> Looks like the commit hash is wrong, should be :
>
> 477c3e1f6363 ("net: stmmac: Introduce dwmac1000 timestamping operations")

Yes, you are absolutely right, I wrongly picked this hash from a custom
branch rather than a stable branch -_- Thanks for spotting this, will be
fixed in v2.

>
> Other than that I agree with the change, these offset are the right
> ones, thanks...
>
> With the Fixes tag fixed,
>
> Reviewed-by: Maxime Chevallier <maxime.chevallier@...tlin.com>

Thanks,

Alexis

-- 
Alexis Lothoré, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com