linux-kernel - Re: [PATCH 0/2] Subject: [PATCH 0/2] clocksource: exynos_mct: Clear timer interrupt when shutting down

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Date:   Mon, 11 Feb 2019 08:14:01 +0100
From:   Marek Szyprowski <m.szyprowski@...sung.com>
To:     Stuart Menefy <stuart.menefy@...hembedded.com>,
        linux-samsung-soc@...r.kernel.org,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Kukjin Kim <kgene@...nel.org>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 0/2] Subject: [PATCH 0/2] clocksource: exynos_mct: Clear
 timer interrupt when shutting down

Hi Stuart

On 2019-02-10 23:51, Stuart Menefy wrote:
> When debugging suspend problems on Exynos 5260, I had a large number
> of debugging prints going to the serial port after interrupts
> had been disabled but before the timer interrupt was shutdown. This
> was long enough for a timer tick to occur, but as interrupts were
> disabled the ISR didn't run, and so the interrupt wasn't cleared.
> Later when the timer was shutdown the interrupt was left asserted and
> so the wfi at the heart of the suspend code didn't wait, causing
> the suspend to fail.
>
> Currently the code which stops the timer when it is on one-shot mode
> and the interrupt occurs is in exynos4_mct_tick_clear(), meaning if we
> called this from the shutdown code exynos4_mct_tick_stop() could be
> called twice. So first restructure the existing code, so the check for
> one-shot mode and stopping the timer is moved to the ISR, leaving
> exynos4_mct_tick_clear() just clearing the interrupt flag.
>
> Once this has been done simply call exynos4_mct_tick_clear() from
> set_state_shutdown().

This also fixes mysterious suspend failures on Odroid XU3/XU4/HC1 :)

Tested-by: Marek Szyprowski <m.szyprowski@...sung.com>

> Stuart Menefy (2):
>   clocksource: exynos_mct: Move one-shot check from tick clear to ISR
>   clocksource: exynos_mct: Clear timer interrupt when shutdown
>
>  drivers/clocksource/exynos_mct.c | 23 ++++++++++++-----------
>  1 file changed, 12 insertions(+), 11 deletions(-)
>
Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland