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

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Date:   Sat, 28 Aug 2021 00:01:05 +0200
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Guenter Roeck <linux@...ck-us.net>,
        Andrew Jeffery <andrew@...id.au>
Cc:     Daniel Lezcano <daniel.lezcano@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Cédric Le Goater <clg@...d.org>,
        Joel Stanley <joel@....id.au>
Subject: Re: [PATCH 2/2] clocksource/drivers/fttmr010: Be stricter on IRQs

On Sat, Aug 21, 2021 at 6:20 AM Guenter Roeck <linux@...ck-us.net> 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@...d.org>
> > Cc: Joel Stanley <joel@....id.au>
> > Signed-off-by: Linus Walleij <linus.walleij@...aro.org>
>
> 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.

Andrew: have you tested this when developing the
QEMU driver?

Yours,
Linus Walleij