From: Thomas Gleixner <tglx@linutronix.de>
To: Alexandre Belloni <alexandre.belloni@bootlin.com>
Cc: John Stultz <john.stultz@linaro.org>,
Stephen Boyd <sboyd@kernel.org>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] alarmtimer: check RTC features instead of ops
Date: Fri, 30 Apr 2021 10:59:53 +0200 [thread overview]
Message-ID: <871rasf8qe.ffs@nanos.tec.linutronix.de> (raw)
In-Reply-To: <YIu7ZqowGScElHBr@piout.net>
On Fri, Apr 30 2021 at 10:10, Alexandre Belloni wrote:
> On 30/04/2021 09:16:40+0200, Thomas Gleixner wrote:
>> On Thu, Apr 29 2021 at 23:49, Alexandre Belloni wrote:
>> > Test RTC_FEATURE_ALARM instead of relying on ops->set_alarm to know whether
>> > alarms are available.
>> >
>> > Fixes: 7ae41220ef58 ("rtc: introduce features bitfield")
>> > Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
>> > ---
>> > Hello,
>> >
>> > This doesn't seem much but this solve an issue where following a change in the
>> > RTC driver, this part of the code will think the RTC is alarm capable while it
>> > is not, then breaking the alarmtimer functionnality.
>>
>> So a driver has the set_alarm() callback but does not advertise
>> RTC_FEATURE_ALARM for whatever reason and why ever this makes sense.
>>
>
> No, it would be the other way around. The issue happens when you have
> two RTCs, rtc0 is not alarm capable and rtc1 has alarms.
>
> The driver for rtc0 used to not have .set_alarm() to signal it didn't
> support alarms, it then switched to RTC_FEATURE_ALARM, making the
> alarmtimer code select that RTC instead of rtc1, breaking suspend/resume
> on the platform.
I'm even more confused. So RTC0 does not have .set_alarm() but why does
it turn on RTC_FEATURE_ALARM? I'm obviously misinterpreting the above...
Thanks,
tglx
next prev parent reply other threads:[~2021-04-30 9:00 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-29 21:49 [PATCH] alarmtimer: check RTC features instead of ops Alexandre Belloni
2021-04-30 7:16 ` Thomas Gleixner
2021-04-30 8:10 ` Alexandre Belloni
2021-04-30 8:59 ` Thomas Gleixner [this message]
2021-05-03 15:34 ` Alexandre Belloni
2021-05-03 18:00 ` Thomas Gleixner
2021-05-08 0:06 ` Thomas Gleixner
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