linux-kernel - Re: [PATCH v3] i2c: imx-lpi2c: directly return ISR when detect a NACK

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Message-ID: <20230726145158.xhn2c7uzs6xsrguf@intel.intel>
Date:   Wed, 26 Jul 2023 16:51:58 +0200
From:   Andi Shyti <andi.shyti@...nel.org>
To:     carlos.song@....com
Cc:     aisheng.dong@....com, shawnguo@...nel.org, s.hauer@...gutronix.de,
        kernel@...gutronix.de, festevam@...il.com, xiaoning.wang@....com,
        haibo.chen@....com, linux-imx@....com, linux-i2c@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] i2c: imx-lpi2c: directly return ISR when detect a NACK

Hi Carlos,

On Wed, Jul 26, 2023 at 05:23:50PM +0800, carlos.song@....com wrote:
> From: Carlos Song <carlos.song@....com>
> 
> A NACK flag in ISR means i2c bus error. In such condition,
> there is no need to do read/write operation.
> 
> In this patch, i2c will check MSR_NDF, MSR_RDF and MSR_TDF
> flag in turn, it's making mutually exclusive NACK/read/write.
> So when a NACK is received(MSR_NDF), i2c will return ISR
> directly and then stop i2c transfer.

Very good, thank you!

> Fixes: a55fa9d0e42e ("i2c: imx-lpi2c: add low power i2c bus driver")

One last little question here. I want to know if this is actually
fixing something or cleaning the exit path. What I mean is:
can the device ever send an NDF along with an RDF or TDF?

If not, this "Fixes:" tag should be removed and this patch can be
considered a cleanup. Otherwise would be nice to know what
failure are you fixing.

I'm just trying to understand here :)

Andi