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From: Marc Zyngier <marc.zyngier@arm.com>
To: Guenter Roeck <linux@roeck-us.net>
Cc: linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org,
	Russell King <linux@arm.linux.org.uk>,
	Will Deacon <will.deacon@arm.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Mark Rutland <mark.rutland@arm.com>,
	Daniel Lezcano <daniel.lezcano@linaro.org>,
	Wim Van Sebroeck <wim@linux-watchdog.org>,
	Valentin Schneider <valentin.schneider@arm.com>
Subject: Re: [PATCH 2/7] watchdog/sbsa: Use arch_timer_read_counter instead of arch_counter_get_cntvct
Date: Tue, 9 Apr 2019 08:43:01 +0100	[thread overview]
Message-ID: <49c5a522-585f-4c05-6acf-0930a3b0670b@arm.com> (raw)
In-Reply-To: <20190408180751.GA28778@roeck-us.net>

On 08/04/2019 19:07, Guenter Roeck wrote:
> On Mon, Apr 08, 2019 at 04:49:02PM +0100, Marc Zyngier wrote:
>> Only arch_timer_read_counter will guarantee that workarounds are
>> applied. So let's use this one instead of arch_counter_get_cntvct.
>>
>> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
> 
> Reviewed-by: Guenter Roeck <linux@roeck-us.net>
> 
> ... assuming/hoping that those counters are actually the same.

There is only a single counter. It is just that in a number of cases,
the HW will return nonsensical values, which is a bit annoying if you
end-up feeding this garbage to a watchdog.

arch_timer_read_counter() guarantees that *if* there is a workaround for
the timer, it gets applied. arch_counter_get_cntvct() only returns the
raw value, with potential side effects.

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...

  reply	other threads:[~2019-04-09  7:43 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-04-08 15:49 [PATCH 0/7] clocksource/arm_arch_timer: Removing the static branch on errata handling Marc Zyngier
2019-04-08 15:49 ` [PATCH 1/7] ARM: vdso: Remove dependency with the arch_timer driver internals Marc Zyngier
2019-04-08 15:58   ` Mark Rutland
2019-04-15 10:46   ` Marc Zyngier
2019-04-30 14:23   ` Will Deacon
2019-04-08 15:49 ` [PATCH 2/7] watchdog/sbsa: Use arch_timer_read_counter instead of arch_counter_get_cntvct Marc Zyngier
2019-04-08 15:59   ` Mark Rutland
2019-04-08 18:07   ` Guenter Roeck
2019-04-09  7:43     ` Marc Zyngier [this message]
2019-04-08 15:49 ` [PATCH 3/7] arm64: " Marc Zyngier
2019-04-08 15:59   ` Mark Rutland
2019-04-08 15:49 ` [PATCH 4/7] clocksource/arm_arch_timer: Direcly assign set_next_event workaround Marc Zyngier
2019-04-08 16:02   ` Mark Rutland
2019-04-11 17:17   ` Daniel Lezcano
2019-04-15 10:18     ` Marc Zyngier
2019-04-08 15:49 ` [PATCH 5/7] clocksource/arm_arch_timer: Drop use of static key in arch_timer_reg_read_stable Marc Zyngier
2019-04-08 16:04   ` Mark Rutland
2019-04-15 11:04   ` Daniel Lezcano
2019-04-08 15:49 ` [PATCH 6/7] clocksource/arm_arch_timer: Remove use of workaround static key Marc Zyngier
2019-04-08 16:05   ` Mark Rutland
2019-04-15 11:07   ` Daniel Lezcano
2019-04-08 15:49 ` [PATCH 7/7] clocksource/arm_arch_timer: Use arch_timer_read_counter to access stable counters Marc Zyngier
2019-04-08 16:08   ` Mark Rutland
2019-04-15 12:16   ` Daniel Lezcano
2019-04-30 15:27     ` Marc Zyngier
2019-04-30 15:39       ` Valentin Schneider
2019-05-03 20:32         ` Daniel Lezcano
2019-05-03 20:31       ` Daniel Lezcano

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