linux-kernel - Re: [PATCH] i2c: stm32f7: Add atomic

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Message-Id: <9BEDFE6D-AE5E-46F1-A1BF-A19C6F5130F6@geanix.com>
Date:   Mon, 3 Jul 2023 11:00:31 +0200
From:   Sean Nyekjaer <sean@...nix.com>
To:     Wolfram Sang <wsa@...nel.org>
Cc:     Pierre-Yves MORDRET <pierre-yves.mordret@...s.st.com>,
        Alain Volmat <alain.volmat@...s.st.com>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        linux-i2c@...r.kernel.org,
        linux-stm32@...md-mailman.stormreply.com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] i2c: stm32f7: Add atomic_xfer method to driver



> On 23 Jun 2023, at 12.33, Wolfram Sang <wsa@...nel.org> wrote:
> 
> On Tue, May 09, 2023 at 03:21:59PM +0200, Sean Nyekjaer wrote:
>> Add an atomic_xfer method to the driver so that it behaves correctly
>> when controlling a PMIC that is responsible for device shutdown.
>> 
>> The atomic_xfer method added is similar to the one from the i2c-mv64xxx
>> driver. When running an atomic_xfer a bool flag in the driver data is
>> set, the interrupt is not unmasked on transfer start, and the IRQ
>> handler is manually invoked while waiting for pending transfers to
>> complete.
>> 
>> Signed-off-by: Sean Nyekjaer <sean@...nix.com>
> 
> Pierre-Yves, Alain, any further comments to this patch?
> 
>> Is it okay to keep the DMA transfer in atomic?
> 
> Will DMA actually run in atomic mode?
> 

Hi Wolfram,

Atomic is mainly(only) used for writing a single register in the PMIC for the stpmic. Guess that will not trigger any DMA use.
But let’s wait for other comments…

/Sean