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

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Message-ID: <525C3E2F.2030109@codeaurora.org>
Date:	Mon, 14 Oct 2013 11:55:43 -0700
From:	Stephen Boyd <sboyd@...eaurora.org>
To:	Kevin Hilman <khilman@...aro.org>
CC:	John Stultz <john.stultz@...aro.org>, linux-kernel@...r.kernel.org,
	linux-arm-msm@...r.kernel.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 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().
Can you try this patch?

----8<----

diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c
index 5d52789..865ecd8 100644
--- a/drivers/clocksource/arm_arch_timer.c
+++ b/drivers/clocksource/arm_arch_timer.c
@@ -420,6 +420,9 @@ static void __init arch_counter_register(unsigned type)
 	cyclecounter.mult = clocksource_counter.mult;
 	cyclecounter.shift = clocksource_counter.shift;
 	timecounter_init(&timecounter, &cyclecounter, start_count);
+
+	/* 56 bits minimum, so we assume worst case rollover */
+	sched_clock_register(arch_timer_read_counter, 56, arch_timer_rate);
 }
 
 static void arch_timer_stop(struct clock_event_device *clk)
@@ -472,15 +475,6 @@ 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,

-- 
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