Re: [RFC PATCH 3/3] rtc: at91sam9: properly act when IRQ handler is called in suspended state

Boris Brezillon
2015-02-26T08:12:51Z

On Wed, 25 Feb 2015 23:05:36 +0100
"Rafael J. Wysocki" <rjw@rjwysocki.net> wrote:

> On Tuesday, February 24, 2015 10:56:02 AM Boris Brezillon wrote:
> > The IRQ line used by the RTC device is often shared with the system timer
> > (PIT) on at91 platforms.
> > Since timers are registering their handlers with IRQF_NO_SUSPEND, we should
> > expect being called in suspended state, and properly wake the system up
> > when this is the case.
> >
> > Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
> > ---
> > drivers/rtc/rtc-at91sam9.c | 62 ++++++++++++++++++++++++++++++++++++++--------
> > 1 file changed, 51 insertions(+), 11 deletions(-)
> >
> > diff --git a/drivers/rtc/rtc-at91sam9.c b/drivers/rtc/rtc-at91sam9.c
> > index 2183fd2..8cf9c1b 100644
> > --- a/drivers/rtc/rtc-at91sam9.c
> > +++ b/drivers/rtc/rtc-at91sam9.c
> > @@ -77,6 +77,8 @@ struct sam9_rtc {
> > unsigned int gpbr_offset;
> > int irq;
> > struct clk *sclk;
> > + unsigned long events;
> > + spinlock_t lock;
> > };
> >
> > #define rtt_readl(rtc, field) \
> > @@ -271,14 +273,9 @@ static int at91_rtc_proc(struct device *dev, struct seq_file *seq)
> > return 0;
> > }
> >
> > -/*
> > - * IRQ handler for the RTC
> > - */
> > -static irqreturn_t at91_rtc_interrupt(int irq, void *_rtc)
> > +static irqreturn_t at91_rtc_cache_events(struct sam9_rtc *rtc)
> > {
> > - struct sam9_rtc *rtc = _rtc;
> > u32 sr, mr;
> > - unsigned long events = 0;
> >
> > /* Shared interrupt may be for another device. Note: reading
> > * SR clears it, so we must only read it in this irq handler!
> > @@ -290,18 +287,54 @@ static irqreturn_t at91_rtc_interrupt(int irq, void *_rtc)
> >
> > /* alarm status */
> > if (sr & AT91_RTT_ALMS)
> > - events |= (RTC_AF | RTC_IRQF);
> > + rtc->events |= (RTC_AF | RTC_IRQF);
> >
> > /* timer update/increment */
> > if (sr & AT91_RTT_RTTINC)
> > - events |= (RTC_UF | RTC_IRQF);
> > + rtc->events |= (RTC_UF | RTC_IRQF);
> > +
> > + return IRQ_HANDLED;
> > +}
> > +
> > +static void at91_rtc_flush_events(struct sam9_rtc *rtc)
> > +{
> > + if (!rtc->events)
> > + return;
> >
> > - rtc_update_irq(rtc->rtcdev, 1, events);
> > + rtc_update_irq(rtc->rtcdev, 1, rtc->events);
> > + rtc->events = 0;
> >
> > pr_debug("%s: num=%ld, events=0x%02lx\n", __func__,
> > - events >> 8, events & 0x000000FF);
> > + rtc->events >> 8, rtc->events & 0x000000FF);
> > +}
> >
> > - return IRQ_HANDLED;
> > +/*
> > + * IRQ handler for the RTC
> > + */
> > +static irqreturn_t at91_rtc_interrupt(int irq, void *_rtc)
> > +{
> > + struct sam9_rtc *rtc = _rtc;
> > + int ret;
> > +
> > + spin_lock(&rtc->lock);
> > +
> > + ret = at91_rtc_cache_events(rtc);
> > +
> > + /* We're called in suspended state */
> > + if (irq_is_wakeup_armed(irq)) {
>
> Instead of doing this, I would set a flag in the driver's ->suspend
> callback (or in ->suspend_late, whichever is more convenient) and check
> that flag here.

Sure, if I can start acting as a suspended handler (in other words, if
I can safely call pm_system_wakeup) as soon as my suspend callback has
been called, then I'm fine adding a boolean to store the device state.

Thanks for your review.

Boris

--
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering