Re: [PATCH 2/2] clocksource/drivers/fttmr010: Be stricter on IRQs

[Guenter Roeck]

On 8/27/21 3:01 PM, Linus Walleij wrote:
> On Sat, Aug 21, 2021 at 6:20 AM Guenter Roeck <linux@xxxxxxxxxxxx> wrote:
> > On Sun, Jul 25, 2021 at 12:44:24AM +0200, Linus Walleij wrote:
>
> > > Make sure we check that the right interrupt occurred before
> > > calling the event handler for timer 1. Report spurious IRQs
> > > as IRQ_NONE.
> > >
> > > Cc: Cédric Le Goater <clg@xxxxxxxx>
> > > Cc: Joel Stanley <joel@xxxxxxxxx>
> > > Signed-off-by: Linus Walleij <linus.walleij@xxxxxxxxxx>
> >
> > This patch results in boot stalls with several qemu aspeed emulations
> > (quanta-q71l-bmc, palmetto-bmc, witherspoon-bmc, ast2500-evb,
> > romulus-bmc, g220a-bmc). Reverting this patch together with
> > "clocksource/drivers/fttmr010: Clear also overflow bit on AST2600"
> > fixes the problem. Bisect log is attached.
>
> Has it been tested on real hardware?
>
> We are reading register 0x34 TIMER_INTR_STATE for this.
> So this should reflect the state of raw interrupts from the timers.
>
> I looked in qemu/hw/timer/aspeed_timer.c
> and the aspeed_timer_read() looks dubious.
> It rather looks like this falls down to returning whatever
> was written to this register and not reflect which IRQ
> was fired at all.

Interesting question. There is aspeed_timer_read(), which doesn't return
anything useful for register 0x34, and there is aspeed_{2400,2500,2600}_timer_read,
which does. No idea what is actually executed.

Guenter

> Andrew: have you tested this when developing the
> QEMU driver?
>
> Yours,
> Linus Walleij