linux-kernel - Re: [PATCH v0 linux master] i2c/busses: Avoid i2c interrupt status clear race condition.

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Message-ID: <232b9fac588beb4d024ab496b118c51af2b0ecba.camel@kernel.crashing.org>
Date:   Thu, 30 Apr 2020 20:55:48 +1000
From:   Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:     Wolfram Sang <wsa@...-dreams.de>,
        Ryan Chen <ryan_chen@...eedtech.com>
Cc:     Brendan Higgins <brendanhiggins@...gle.com>,
        Joel Stanley <joel@....id.au>,
        Andrew Jeffery <andrew@...id.au>,
        "linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>,
        "openbmc@...ts.ozlabs.org" <openbmc@...ts.ozlabs.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-aspeed@...ts.ozlabs.org" <linux-aspeed@...ts.ozlabs.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v0 linux master] i2c/busses: Avoid i2c interrupt status
 clear race condition.

On Wed, 2020-04-29 at 11:03 +0200, Wolfram Sang wrote:
> > And is there maybe a Fixes: tag for it?
> > [Ryan Chen] Yes it is a fix patch.
> 
> I meant this (from submitting-patches.rst):

It fixes the original implementation of the driver basically. It's just
a classic posted-write fix. The write to clear the pending interrupt is
asynchronous, so you can get spurrious ones if you return from the
handler before it has percolated to the HW.

I assume it's just more visible on the 2600 because of the cores are
significantly faster but the IO bus is still as dumb.

Ryan: You could always add a Fixed-by: tag that specifies the commit
that added the initial driver...

Cheers,
Ben.