linux-kernel - Re: [PATCH v4 05/17] arch_timer: Move to generic sched

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Message-ID: <CALAqxLUVnL08HJw0CAGabKEGKuSPPNx-GUF_jPX6v0cZ4LZHDg@mail.gmail.com>
Date:	Mon, 14 Oct 2013 13:14:57 -0700
From:	John Stultz <john.stultz@...aro.org>
To:	Stephen Boyd <sboyd@...eaurora.org>
Cc:	Kevin Hilman <khilman@...aro.org>,
	lkml <linux-kernel@...r.kernel.org>,
	"linux-arm-msm@...r.kernel.org" <linux-arm-msm@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Russell King <linux@....linux.org.uk>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>,
	Christopher Covington <cov@...eaurora.org>,
	Olof Johansson <olof@...om.net>
Subject: Re: [PATCH v4 05/17] arch_timer: Move to generic sched_clock framework

On Mon, Oct 14, 2013 at 11:55 AM, Stephen Boyd <sboyd@...eaurora.org> wrote:
> On 10/14/13 11:44, Kevin Hilman wrote:
>> Stephen Boyd <sboyd@...eaurora.org> writes:
>>
>>> Register with the generic sched_clock framework now that it
>>> supports 64 bits. This fixes two problems with the current
>>> sched_clock support for machines using the architected timers.
>>> First off, we don't subtract the start value from subsequent
>>> sched_clock calls so we can potentially start off with
>>> sched_clock returning gigantic numbers. Second, there is no
>>> support for suspend/resume handling so problems such as discussed
>>> in 6a4dae5 (ARM: 7565/1: sched: stop sched_clock() during
>>> suspend, 2012-10-23) can happen without this patch. Finally, it
>>> allows us to move the sched_clock setup into drivers clocksource
>>> out of the arch ports.
>>>
>>> Cc: Christopher Covington <cov@...eaurora.org>
>>> Cc: Catalin Marinas <catalin.marinas@....com>
>>> Signed-off-by: Stephen Boyd <sboyd@...eaurora.org>
>> A boot failure on Exynos5/Arndale showed up in next-20131014[1], and a
>> subsequent bisect has fingered this patch as the culprit.
>>
>> I haven't had a chance to debug this any further, but wanted to share in
>> case someone else can debug.
>>
>> The console log is below, but don't think there is much useful there as
>> it shows nothing after the 'Starting kernel ...' from u-boot.
>
> debug_ll output would be nice. Anyway, that patch looks "weird". It is
> definitely not what I sent out. Most notably, this hunk jumps out
>
> @@ -471,6 +472,15 @@ static int __init arch_timer_register(void)
>                 goto out;
>         }
>
> +       clocksource_register_hz(&clocksource_counter, arch_timer_rate);
> +       cyclecounter.mult = clocksource_counter.mult;
> +       cyclecounter.shift = clocksource_counter.shift;
> +       timecounter_init(&timecounter, &cyclecounter,
> +                        arch_counter_get_cntvct());
> +
> +       /* 56 bits minimum, so we assume worst case rollover */
> +       sched_clock_register(arch_timer_read_counter, 56, arch_timer_rate);
> +
>         if (arch_timer_use_virtual) {
>                 ppi = arch_timer_ppi[VIRT_PPI];
>                 err = request_percpu_irq(ppi, arch_timer_handler_virt,
>
>
> Which is adding the clocksource_register_hz() and timecounter_init()
> call twice. It should only be adding the sched_clock_register() call and
> the sched_clock_register() call should be in arch_counter_register().

Sorry, that's my fault. That bit collided when I applied the patch
onto my queue.

thanks
-john
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