From: Guenter Roeck <linux@roeck-us.net>
To: Linus Walleij <linus.walleij@linaro.org>,
Andrew Jeffery <andrew@aj.id.au>
Cc: "Daniel Lezcano" <daniel.lezcano@linaro.org>,
"Thomas Gleixner" <tglx@linutronix.de>,
linux-kernel <linux-kernel@vger.kernel.org>,
"Cédric Le Goater" <clg@kaod.org>,
"Joel Stanley" <joel@jms.id.au>
Subject: Re: [PATCH 2/2] clocksource/drivers/fttmr010: Be stricter on IRQs
Date: Fri, 27 Aug 2021 20:37:56 -0700 [thread overview]
Message-ID: <4d87c7af-d2e3-9456-130a-b35b507ff3a2@roeck-us.net> (raw)
In-Reply-To: <CACRpkdYObGTWni3sSa21iNsgikzj7t9MA6y4TNgkBTTYQt+coA@mail.gmail.com>
On 8/27/21 3:01 PM, Linus Walleij wrote:
> On Sat, Aug 21, 2021 at 6:20 AM Guenter Roeck <linux@roeck-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@kaod.org>
>>> Cc: Joel Stanley <joel@jms.id.au>
>>> Signed-off-by: Linus Walleij <linus.walleij@linaro.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.
>
Actually, no. Turns out the qemu code is just a bit difficult to understand.
The code in question is:
default:
value = ASPEED_TIMER_GET_CLASS(s)->read(s, offset);
break;
For ast2500-evb, that translates to a call to aspeed_2500_timer_read().
Here is a trace example (after adding some more tracing):
aspeed_2500_timer_read From 0x34: 0x0
aspeed_timer_read From 0x34: of size 4: 0x0
Problem is that - at least in qemu - only the 2600 uses register 0x34
for the interrupt status. On the 2500, 0x34 is the ctrl2 register.
Indeed, the patch works fine on, for example, ast2600-evb.
It only fails on ast2400 and ast2500 boards.
I don't have the manuals, so I can't say what the correct behavior is,
but at least there is some evidence that TIMER_INTR_STATE may not exist
on ast2400 and ast2500 SOCs. From drivers/clocksource/timer-fttmr010.c:
/*
* Interrupt status/mask register definitions for fttmr010/gemini/moxart
* timers.
* The registers don't exist and they are not needed on aspeed timers
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
* because:
* - aspeed timer overflow interrupt is controlled by bits in Control
* Register (TMC30).
* - aspeed timers always generate interrupt when either one of the
* Match registers equals to Status register.
*/
Guenter
next prev parent reply other threads:[~2021-08-28 3:38 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-24 22:44 [PATCH 1/2] clocksource/drivers/fttmr010: Pass around less pointers Linus Walleij
2021-07-24 22:44 ` [PATCH 2/2] clocksource/drivers/fttmr010: Be stricter on IRQs Linus Walleij
2021-08-20 8:53 ` Daniel Lezcano
2021-08-20 13:39 ` Linus Walleij
2021-08-20 14:16 ` Daniel Lezcano
2021-08-21 4:20 ` Guenter Roeck
2021-08-21 8:04 ` Daniel Lezcano
2021-08-27 22:01 ` Linus Walleij
2021-08-27 22:31 ` Guenter Roeck
2021-08-28 3:37 ` Guenter Roeck [this message]
2021-08-28 8:08 ` Cédric Le Goater
2021-08-30 4:16 ` Andrew Jeffery
2021-08-30 4:58 ` [PATCH 2/2]: Be stric clocksource/drivers/fttmr010ter " Guenter Roeck
2021-08-30 6:30 ` Andrew Jeffery
2021-08-30 7:47 ` [PATCH 2/2]: Be stric clocksource/drivers/fttmr010 " Cédric Le Goater
2021-08-30 15:24 ` Guenter Roeck
2021-09-01 23:38 ` [PATCH 2/2] clocksource/drivers/fttmr010: Be stricter " Joel Stanley
2021-08-26 16:25 ` [tip: timers/core] clocksource/drivers/fttmr010: Pass around less pointers tip-bot2 for Linus Walleij
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