linux-kernel - Re: [PATCH] rtc: cros-ec: Limit RTC alarm range if needed

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Date:   Fri, 28 Oct 2022 18:50:54 -0700
From:   Brian Norris <briannorris@...omium.org>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     Alessandro Zummo <a.zummo@...ertech.it>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Benson Leung <bleung@...omium.org>, linux-rtc@...r.kernel.org,
        chrome-platform@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] rtc: cros-ec: Limit RTC alarm range if needed

On Fri, Oct 28, 2022 at 05:54:00PM -0700, Guenter Roeck wrote:
> RTC chips on some older Chromebooks can only handle alarms less than 24
> hours in the future. Attempts to set an alarm beyond that range fails.
> The most severe impact of this limitation is that suspend requests fail
> if alarmtimer_suspend() tries to set an alarm for more than 24 hours
> in the future.
> 
> Try to set the real-time alarm to just below 24 hours if setting it to
> a larger value fails to work around the problem. While not perfect, it
> is better than just failing the call. A similar workaround is already
> implemented in the rtc-tps6586x driver.
> 
> Drop error messages in cros_ec_rtc_get() and cros_ec_rtc_set() since the
> calling code also logs an error and to avoid spurious error messages if
> setting the alarm ultimately succeeds.
> 
> Cc: Brian Norris <briannorris@...omium.org>
> Signed-off-by: Guenter Roeck <linux@...ck-us.net>

Reviewed-by: Brian Norris <briannorris@...omium.org>
Tested-by: Brian Norris <briannorris@...omium.org>