linux-kernel - Re: [PATCH v2 1/2] rtc-cmos: Ensure no expired alarm is left enabled after resume

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Date:   Tue, 6 Sep 2016 11:47:39 +0200
From:   Gabriele Mazzotta <gabriele.mzt@...il.com>
To:     Alexandre Belloni <alexandre.belloni@...e-electrons.com>
Cc:     Alessandro Zummo <a.zummo@...ertech.it>,
        rtc-linux@...glegroups.com,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        matthew.garrett@...ula.com
Subject: Re: [PATCH v2 1/2] rtc-cmos: Ensure no expired alarm is left enabled
 after resume

2016-09-06 0:26 GMT+02:00 Alexandre Belloni
<alexandre.belloni@...e-electrons.com>:
> Hi
>
> On 01/09/2016 at 00:58:59 +0200, Gabriele Mazzotta wrote :
>>  static int cmos_resume(struct device *dev)
>>  {
>>       struct cmos_rtc *cmos = dev_get_drvdata(dev);
>>       unsigned char tmp;
>> +     bool is_wkalrm_expired;
>>
>>       if (cmos->enabled_wake) {
>>               if (cmos->wake_off)
>> @@ -913,6 +935,8 @@ static int cmos_resume(struct device *dev)
>>               cmos->enabled_wake = 0;
>>       }
>>
>> +     is_wkalrm_expired = cmos_is_wkalrm_expired(dev);
>> +
>>       spin_lock_irq(&rtc_lock);
>>       tmp = cmos->suspend_ctrl;
>>       cmos->suspend_ctrl = 0;
>> @@ -939,6 +963,17 @@ static int cmos_resume(struct device *dev)
>>                       tmp &= ~RTC_AIE;
>>                       hpet_mask_rtc_irq_bit(RTC_AIE);
>>               } while (mask & RTC_AIE);
>> +
>> +             /*
>> +              * If RTC_AIE is set and we have an alarm set to go off in the
>> +              * past, then the BIOS woke the system when the alarm went off
>> +              * and we now have to clear it.
>> +              */
>> +             if ((tmp & RTC_AIE) && is_wkalrm_expired) {
>
> Is there any issue dropping is_wkalrm_expired and calling
> cmos_is_wkalrm_expired() here? That would avoid calling
> cmos_is_wkalrm_expired on each wakeup.

Yes, get_rtc_time() (cmos_read_time()) tries to aquire rtc_lock.

> --
> Alexandre Belloni, Free Electrons
> Embedded Linux and Kernel engineering
> http://free-electrons.com