linux-kernel - Re: [PATCH] regmap: kunit: fix raw noinc write test wrapping

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Message-ID: <1bf36657-0169-4d10-960f-ba01dba0411b@roeck-us.net>
Date: Tue, 6 Feb 2024 08:43:31 -0800
From: Guenter Roeck <linux@...ck-us.net>
To: Mark Brown <broonie@...nel.org>,
 Ben Wolsieffer <ben.wolsieffer@...ring.com>
Cc: linux-kernel@...r.kernel.org,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 "Rafael J. Wysocki" <rafael@...nel.org>
Subject: Re: [PATCH] regmap: kunit: fix raw noinc write test wrapping

On 2/6/24 07:38, Mark Brown wrote:
> On Tue, Feb 06, 2024 at 10:10:05AM -0500, Ben Wolsieffer wrote:
>> The raw noinc write test places a known value in the register following
>> the noinc register to verify that it is not disturbed by the noinc
>> write. This test ensures this value is distinct by adding 100 to the
>> second element of the noinc write data.
>>
>> The regmap registers are 16-bit, while the test value is stored in an
>> unsigned int. Therefore, adding 100 may cause the register to wrap while
>> the test value does not, causing the test to fail. This patch fixes this
>> by changing val_test and val_last from unsigned int to u16.
> 
> Ah, that'd do it!  I wonder why Guenter is seeing this with much greater
> frequency than I am, I have managed to reproduce a few times this
> afternoon but very rarely.  Guenter, does this fix the issues you're
> seeing?

Give me a bit. It takes ~2 hours for a complete test run.

I am not surprised that you didn't see the problem easily. I am running
more than 500 boot tests on each release, and only saw it in four of them
when testing v6.8-rc3. So I'd expect a "hit" rate of about 1%.

Thanks,
Guenter