linux-kernel - Re: [PATCH v5 0/9] rtc-cmos,rtc-mc146818-lib: fixes

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Message-ID: <Ydg6EnPdWjB3Vznc@piout.net>
Date:   Fri, 7 Jan 2022 14:03:14 +0100
From:   Alexandre Belloni <alexandre.belloni@...tlin.com>
To:     Mateusz Jończyk <mat.jonczyk@...pl>
Cc:     linux-rtc@...r.kernel.org, linux-kernel@...r.kernel.org,
        Alessandro Zummo <a.zummo@...ertech.it>,
        Greg KH <gregkh@...uxfoundation.org>
Subject: Re: [PATCH v5 0/9] rtc-cmos,rtc-mc146818-lib: fixes

Hi,

On 07/01/2022 13:49:25+0100, Mateusz Jończyk wrote:
> Hello,
> 
> This patch series fixes some issues in the RTC CMOS handling code:
> 
> 1. A missing spin_lock_irq() / spin_unlock_irq() pair in cmos_set_alarm().
> 2. A failing presence check of the RTC: the clock was misdetected as
>    broken since Linux 5.11 on one of our home systems.
> 3. Do not touch the RTC alarm registers when the RTC update is in
>    progress. (On some Intel chipsets, this causes bogus values being
>    read or writes to fail silently.)
> 
> This is my first patch series, so please review carefully.
> 
> v2: Drop the last patch:
>         Revert "rtc: cmos: Replace spin_lock_irqsave with spin_lock in hard IRQ"
> which was made obsolete by mainlining of 
> commit 13be2efc390a ("rtc: cmos: Disable irq around direct invocation of cmos_interrupt()")
> 
> v3: Rework solution to problem 3 (I'd like to thank Greg KH for comment),
> drop x86 refactoring patches (I'll send them later).
> 
> v4: Fixed some issues pointed out by Mr Alexandre Belloni:
>     - do not add strings to rtc-mc146818-lib.c - I moved the error printing
>       code to callers of mc146818_get_time(). This resulted in two new
>       patches in the series,
>     - other small issues.
> 
> v5: Increase maximum accepted duration of the UIP high pulse from 10 to 20ms,
>     in case there are some very slow chips out there.
> 
>     Note: this may cause problems with hpet_rtc_interrupt() if the CMOS
>     RTC stops working while the system is running and RTC update
>     interrupt / RTC alarm interrupt is enabled (which should be rare).
>     In this case, hpet_rtc_interrupt() is executed 64 times per second
>     and takes up to 20ms to complete - which may constantly occupy
>     one CPU. I am not sure if this is likely enough to implement
>     special handling of this case in hpet_rtc_interrupt().
> 

Because v4 has been applied, you'd have to send a series against
rtc-next.

-- 
Alexandre Belloni, co-owner and COO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com