All of lore.kernel.org
 help / color / mirror / Atom feed
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...

WARNING: multiple messages have this Message-ID (diff)
From: Marc Zyngier <marc.zyngier@arm.com>
To: Guenter Roeck <linux@roeck-us.net>
Cc: Mark Rutland <mark.rutland@arm.com>,
	Russell King <linux@arm.linux.org.uk>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Daniel Lezcano <daniel.lezcano@linaro.org>,
	Will Deacon <will.deacon@arm.com>,
	linux-kernel@vger.kernel.org,
	Wim Van Sebroeck <wim@linux-watchdog.org>,
	Valentin Schneider <valentin.schneider@arm.com>,
	linux-arm-kernel@lists.infradead.org
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...

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

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

Thread overview: 56+ 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 ` 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 15:49   ` Marc Zyngier
2019-04-08 15:58   ` Mark Rutland
2019-04-08 15:58     ` Mark Rutland
2019-04-15 10:46   ` Marc Zyngier
2019-04-15 10:46     ` Marc Zyngier
2019-04-30 14:23   ` Will Deacon
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 15:49   ` Marc Zyngier
2019-04-08 15:59   ` Mark Rutland
2019-04-08 15:59     ` Mark Rutland
2019-04-08 18:07   ` Guenter Roeck
2019-04-08 18:07     ` Guenter Roeck
2019-04-09  7:43     ` Marc Zyngier [this message]
2019-04-09  7:43       ` Marc Zyngier
2019-04-08 15:49 ` [PATCH 3/7] arm64: " Marc Zyngier
2019-04-08 15:49   ` Marc Zyngier
2019-04-08 15:59   ` Mark Rutland
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 15:49   ` Marc Zyngier
2019-04-08 16:02   ` Mark Rutland
2019-04-08 16:02     ` Mark Rutland
2019-04-11 17:17   ` Daniel Lezcano
2019-04-11 17:17     ` Daniel Lezcano
2019-04-15 10:18     ` Marc Zyngier
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 15:49   ` Marc Zyngier
2019-04-08 16:04   ` Mark Rutland
2019-04-08 16:04     ` Mark Rutland
2019-04-15 11:04   ` Daniel Lezcano
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 15:49   ` Marc Zyngier
2019-04-08 16:05   ` Mark Rutland
2019-04-08 16:05     ` Mark Rutland
2019-04-15 11:07   ` Daniel Lezcano
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 15:49   ` Marc Zyngier
2019-04-08 16:08   ` Mark Rutland
2019-04-08 16:08     ` Mark Rutland
2019-04-15 12:16   ` Daniel Lezcano
2019-04-15 12:16     ` Daniel Lezcano
2019-04-30 15:27     ` Marc Zyngier
2019-04-30 15:27       ` Marc Zyngier
2019-04-30 15:39       ` Valentin Schneider
2019-04-30 15:39         ` Valentin Schneider
2019-05-03 20:32         ` Daniel Lezcano
2019-05-03 20:32           ` Daniel Lezcano
2019-05-03 20:31       ` Daniel Lezcano
2019-05-03 20:31         ` Daniel Lezcano

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=49c5a522-585f-4c05-6acf-0930a3b0670b@arm.com \
    --to=marc.zyngier@arm.com \
    --cc=catalin.marinas@arm.com \
    --cc=daniel.lezcano@linaro.org \
    --cc=linux-arm-kernel@lists.infradead.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux@arm.linux.org.uk \
    --cc=linux@roeck-us.net \
    --cc=mark.rutland@arm.com \
    --cc=valentin.schneider@arm.com \
    --cc=will.deacon@arm.com \
    --cc=wim@linux-watchdog.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.