linux-kernel - Re: [PATCH v4 1/2] rtc-cmos: Clear ACPI-driven alarms upon resume

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Message-ID: <20160921200735.nqvs33topaaeq7fv@piout.net>
Date:   Wed, 21 Sep 2016 22:07:35 +0200
From:   Alexandre Belloni <alexandre.belloni@...e-electrons.com>
To:     Gabriele Mazzotta <gabriele.mzt@...il.com>
Cc:     a.zummo@...ertech.it, rtc-linux@...glegroups.com,
        linux-kernel@...r.kernel.org, matthew.garrett@...ula.com
Subject: Re: [PATCH v4 1/2] rtc-cmos: Clear ACPI-driven alarms upon resume

Hi,

Thank you for your perseverance.

On 20/09/2016 at 01:12:43 +0200, Gabriele Mazzotta wrote :
> Currently ACPI-driven alarms are not cleared when they wake the
> system. As consequence, expired alarms must be manually cleared to
> program a new alarm. Fix this by correctly handling ACPI-driven
> alarms.
> 
> More specifically, the ACPI specification [1] provides for two
> alternative implementations of the RTC. Depending on the
> implementation, the driver either clear the alarm from the resume
> callback or from ACPI interrupt handler:
> 
>  - The platform has the RTC wakeup status fixed in hardware
>    (ACPI_FADT_FIXED_RTC is 0). In this case the driver can determine
>    if the RTC was the reason of the wakeup from the resume callback
>    by reading the RTC status register.
> 
>  - The platform has no fixed hardware feature event bits. In this
>    case a GPE is used to wake the system and the driver clears the
>    alarm from its handler.
> 
> [1] http://www.acpi.info/DOWNLOADS/ACPI_5_Errata%20A.pdf
> 
> Signed-off-by: Gabriele Mazzotta <gabriele.mzt@...il.com>
> ---
>  drivers/rtc/rtc-cmos.c | 49 +++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 49 insertions(+)

Applied, with the following cosmetic change:
@@ -982,13 +982,11 @@ static u32 rtc_handler(void *context)
 {
        struct device *dev = context;
        struct cmos_rtc *cmos = dev_get_drvdata(dev);
-       unsigned char rtc_control;
+       unsigned char rtc_control = 0;
        unsigned char rtc_intr;
 
        spin_lock_irq(&rtc_lock);
-       if (!cmos_rtc.suspend_ctrl)
-               rtc_control = cmos_rtc.suspend_ctrl;
-       else
+       if (cmos_rtc.suspend_ctrl)
                rtc_control = CMOS_READ(RTC_CONTROL);
        if (rtc_control & RTC_AIE) {
                cmos_rtc.suspend_ctrl &= ~RTC_AIE;



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