From: Arnd Bergmann <arnd@arndb.de>
To: linux-arm-kernel@lists.infradead.org
Cc: linux-samsung-soc@vger.kernel.org,
Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
Lee Jones <lee.jones@linaro.org>,
Russell King <linux@armlinux.org.uk>,
Krzysztof Kozlowski <krzk@kernel.org>,
linux-kernel@vger.kernel.org,
Javier Martinez Canillas <javier@osg.samsung.com>,
Kukjin Kim <kgene@kernel.org>,
Sylwester Nawrocki <s.nawrocki@samsung.com>,
Tomasz Figa <tomasz.figa@gmail.com>,
Ben Dooks <ben.dooks@codethink.co.uk>,
Marek Szyprowski <m.szyprowski@samsung.com>
Subject: Re: [PATCH] ARM: Drop fixed 200 Hz timer requirement from Exynos platforms
Date: Thu, 17 Nov 2016 13:35:45 +0100 [thread overview]
Message-ID: <3145378.USf2WOPoV2@wuerfel> (raw)
In-Reply-To: <1479148025-469-1-git-send-email-krzk@kernel.org>
On Monday, November 14, 2016 8:27:05 PM CET Krzysztof Kozlowski wrote:
> @@ -1497,7 +1497,7 @@ source kernel/Kconfig.preempt
> config HZ_FIXED
> int
> default 200 if ARCH_EBSA110 || ARCH_S3C24XX || \
> - ARCH_S5PV210 || ARCH_EXYNOS4
> + ARCH_S5PV210
> default 128 if SOC_AT91RM9200
> default 0
After further research, I've concluded that we should also drop the
settings for ARCH_S5PV210 and ARCH_S3C24XX here.
ARCH_S5PV210 behaves exactly like EXYNOS here, it has 32-bit timers
so there won't be any overflow with 100Hz.
For ARCH_S3C24XX, it the requirement was that HZ_100 could not
be used with the old arch/arm/plat-samsung/time.c code that would
overflow its 16-bit counter.
However, the new drivers/clocksource/samsung_pwm_timer.c configures
the clock divider to '50' instead of '6', so there is no longer
a 16-bit overflow before the 100Hz tick, it now overflows every
3.7ms for the typical 12MHz clock.
Arnd
WARNING: multiple messages have this Message-ID (diff)
From: arnd@arndb.de (Arnd Bergmann)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH] ARM: Drop fixed 200 Hz timer requirement from Exynos platforms
Date: Thu, 17 Nov 2016 13:35:45 +0100 [thread overview]
Message-ID: <3145378.USf2WOPoV2@wuerfel> (raw)
In-Reply-To: <1479148025-469-1-git-send-email-krzk@kernel.org>
On Monday, November 14, 2016 8:27:05 PM CET Krzysztof Kozlowski wrote:
> @@ -1497,7 +1497,7 @@ source kernel/Kconfig.preempt
> config HZ_FIXED
> int
> default 200 if ARCH_EBSA110 || ARCH_S3C24XX || \
> - ARCH_S5PV210 || ARCH_EXYNOS4
> + ARCH_S5PV210
> default 128 if SOC_AT91RM9200
> default 0
After further research, I've concluded that we should also drop the
settings for ARCH_S5PV210 and ARCH_S3C24XX here.
ARCH_S5PV210 behaves exactly like EXYNOS here, it has 32-bit timers
so there won't be any overflow with 100Hz.
For ARCH_S3C24XX, it the requirement was that HZ_100 could not
be used with the old arch/arm/plat-samsung/time.c code that would
overflow its 16-bit counter.
However, the new drivers/clocksource/samsung_pwm_timer.c configures
the clock divider to '50' instead of '6', so there is no longer
a 16-bit overflow before the 100Hz tick, it now overflows every
3.7ms for the typical 12MHz clock.
Arnd
WARNING: multiple messages have this Message-ID (diff)
From: Arnd Bergmann <arnd@arndb.de>
To: linux-arm-kernel@lists.infradead.org
Cc: Krzysztof Kozlowski <krzk@kernel.org>,
Russell King <linux@armlinux.org.uk>,
Kukjin Kim <kgene@kernel.org>,
Javier Martinez Canillas <javier@osg.samsung.com>,
linux-samsung-soc@vger.kernel.org, linux-kernel@vger.kernel.org,
Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
Tomasz Figa <tomasz.figa@gmail.com>,
Ben Dooks <ben.dooks@codethink.co.uk>,
Sylwester Nawrocki <s.nawrocki@samsung.com>,
Lee Jones <lee.jones@linaro.org>,
Marek Szyprowski <m.szyprowski@samsung.com>
Subject: Re: [PATCH] ARM: Drop fixed 200 Hz timer requirement from Exynos platforms
Date: Thu, 17 Nov 2016 13:35:45 +0100 [thread overview]
Message-ID: <3145378.USf2WOPoV2@wuerfel> (raw)
In-Reply-To: <1479148025-469-1-git-send-email-krzk@kernel.org>
On Monday, November 14, 2016 8:27:05 PM CET Krzysztof Kozlowski wrote:
> @@ -1497,7 +1497,7 @@ source kernel/Kconfig.preempt
> config HZ_FIXED
> int
> default 200 if ARCH_EBSA110 || ARCH_S3C24XX || \
> - ARCH_S5PV210 || ARCH_EXYNOS4
> + ARCH_S5PV210
> default 128 if SOC_AT91RM9200
> default 0
After further research, I've concluded that we should also drop the
settings for ARCH_S5PV210 and ARCH_S3C24XX here.
ARCH_S5PV210 behaves exactly like EXYNOS here, it has 32-bit timers
so there won't be any overflow with 100Hz.
For ARCH_S3C24XX, it the requirement was that HZ_100 could not
be used with the old arch/arm/plat-samsung/time.c code that would
overflow its 16-bit counter.
However, the new drivers/clocksource/samsung_pwm_timer.c configures
the clock divider to '50' instead of '6', so there is no longer
a 16-bit overflow before the 100Hz tick, it now overflows every
3.7ms for the typical 12MHz clock.
Arnd
next prev parent reply other threads:[~2016-11-17 12:35 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-14 18:27 [PATCH] ARM: Drop fixed 200 Hz timer requirement from Exynos platforms Krzysztof Kozlowski
2016-11-14 18:27 ` Krzysztof Kozlowski
2016-11-17 12:35 ` Arnd Bergmann [this message]
2016-11-17 12:35 ` Arnd Bergmann
2016-11-17 12:35 ` Arnd Bergmann
2016-11-18 6:47 ` Krzysztof Kozlowski
2016-11-18 6:47 ` Krzysztof Kozlowski
2016-11-17 15:40 ` Javier Martinez Canillas
2016-11-17 15:40 ` Javier Martinez Canillas
2016-11-17 15:40 ` Javier Martinez Canillas
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