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

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Date:   Thu, 27 Jul 2023 02:57:55 +0000
From:   Carlos Song <carlos.song@....com>
To:     Andi Shyti <andi.shyti@...nel.org>
CC:     Aisheng Dong <aisheng.dong@....com>,
        "shawnguo@...nel.org" <shawnguo@...nel.org>,
        "s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>,
        "festevam@...il.com" <festevam@...il.com>,
        Clark Wang <xiaoning.wang@....com>,
        Bough Chen <haibo.chen@....com>,
        dl-linux-imx <linux-imx@....com>,
        "linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [EXT] Re: [PATCH v3] i2c: imx-lpi2c: directly return ISR when
 detect a NACK



> -----Original Message-----
> From: Andi Shyti <andi.shyti@...nel.org>
> Sent: Wednesday, July 26, 2023 10:52 PM
> To: Carlos Song <carlos.song@....com>
> Cc: Aisheng Dong <aisheng.dong@....com>; shawnguo@...nel.org;
> s.hauer@...gutronix.de; kernel@...gutronix.de; festevam@...il.com; Clark
> Wang <xiaoning.wang@....com>; Bough Chen <haibo.chen@....com>;
> dl-linux-imx <linux-imx@....com>; linux-i2c@...r.kernel.org;
> linux-arm-kernel@...ts.infradead.org; linux-kernel@...r.kernel.org
> Subject: [EXT] Re: [PATCH v3] i2c: imx-lpi2c: directly return ISR when detect a
> NACK
> 
> Caution: This is an external email. Please take care when clicking links or
> opening attachments. When in doubt, report the message using the 'Report this
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> 
> 
> 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


Hi, Andi,
Yes, no failure to fix just a cleanup. I will remove it and resend v4.