From: Thomas Gleixner <tglx@linutronix.de>
To: Roman Volkov <v1ron@mail.ru>
Cc: arm@kernel.org, linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, Arnd Bergmann <arnd@arndb.de>,
Alexey Charkov <alchark@gmail.com>,
Roman Volkov <rvolkov@v1ros.org>,
Tony Prisk <linux@prisktech.co.nz>,
Daniel Lezcano <daniel.lezcano@linaro.org>
Subject: Re: [PATCH v2 RESEND 1/3] clocksource/vt8500: Use MIN_OSCR_DELTA from PXA
Date: Fri, 1 Jan 2016 10:58:06 +0100 (CET) [thread overview]
Message-ID: <alpine.DEB.2.11.1601011052130.28591@nanos> (raw)
In-Reply-To: <1451584927-4051-2-git-send-email-v1ron@mail.ru>
On Thu, 31 Dec 2015, Roman Volkov wrote:
> From: Roman Volkov <rvolkov@v1ros.org>
>
> Since vt8500 and PXA timers are identical, use MIN_OSCR_DELTA from PXA,
> which is bigger than existing value. It is required to determine the
> minimum delay which hardware can generate.
This changelog makes no sense at all.
> This commit fixes vt8500 breakage in Linux 4.2 introduced by
> c6eb3f7 ('hrtimer: Get rid of hrtimer softirq')
> Signed-off-by: Roman Volkov <rvolkov@v1ros.org>
> ---
> drivers/clocksource/vt8500_timer.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/clocksource/vt8500_timer.c b/drivers/clocksource/vt8500_timer.c
> index a92e94b..dfc3bb4 100644
> --- a/drivers/clocksource/vt8500_timer.c
> +++ b/drivers/clocksource/vt8500_timer.c
> @@ -50,6 +50,8 @@
>
> #define msecs_to_loops(t) (loops_per_jiffy / 1000 * HZ * t)
>
> +#define MIN_OSCR_DELTA 16
> +
> static void __iomem *regbase;
>
> static cycle_t vt8500_timer_read(struct clocksource *cs)
> @@ -80,7 +82,7 @@ static int vt8500_timer_set_next_event(unsigned long cycles,
> cpu_relax();
> writel((unsigned long)alarm, regbase + TIMER_MATCH_VAL);
>
> - if ((signed)(alarm - clocksource.read(&clocksource)) <= 16)
> + if ((signed)(alarm - clocksource.read(&clocksource)) <= MIN_OSCR_DELTA)
So how is that value bigger? MIN_OSCR_DELTA is still 16
> return -ETIME;
>
> writel(1, regbase + TIMER_IER_VAL);
> @@ -151,7 +153,7 @@ static void __init vt8500_timer_init(struct device_node *np)
> pr_err("%s: setup_irq failed for %s\n", __func__,
> clockevent.name);
> clockevents_config_and_register(&clockevent, VT8500_TIMER_HZ,
> - 4, 0xf0000000);
> + MIN_OSCR_DELTA * 2, 0xf0000000);
Now here is the real change. You use a larger minimum tick value so that the
above check in vt8500_timer_set_next_event() actually works. That's what you
want to explain in the changelog. The blurb about reusing MIN_OSCR_DELTA is
just useless.
A proper changelog describes:
1) the problem and the resulting wreckage
2) the solution
Thanks,
tglx
next prev parent reply other threads:[~2016-01-01 9:59 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-12-31 18:02 [PATCH v2 RESEND 0/3] clocksource/vt8500: Fix hangs in small delays Roman Volkov
2015-12-31 18:02 ` [PATCH v2 RESEND 1/3] clocksource/vt8500: Use MIN_OSCR_DELTA from PXA Roman Volkov
2015-12-31 22:33 ` Thomas Gleixner
2015-12-31 23:32 ` Roman Volkov
2016-01-01 20:23 ` Robert Jarzmik
2016-01-01 9:58 ` Thomas Gleixner [this message]
2015-12-31 18:02 ` [PATCH v2 RESEND 2/3] clocksource/vt8500: Remove the 'loops' variable Roman Volkov
2015-12-31 18:02 ` [PATCH v2 RESEND 3/3] clocksource/vt8500: Add register R/W functions Roman Volkov
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