From: daniel.lezcano@linaro•org (Daniel Lezcano)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH] driver: clocksource: fix age-old arch timer C3STOP detection issue
Date: Tue, 15 Apr 2014 18:57:24 +0200 [thread overview]
Message-ID: <534D64F4.3060808@linaro.org> (raw)
In-Reply-To: <1396947872-6673-1-git-send-email-lorenzo.pieralisi@arm.com>
On 04/08/2014 11:04 AM, Lorenzo Pieralisi wrote:
> ARM arch timers are tightly coupled with the CPU logic and lose context
> on platform implementing HW power management when cores are powered
> down at run-time. Marking the arch timers as C3STOP regardless of power
> management capabilities causes issues on platforms with no power management,
> since in that case the arch timers cannot possibly enter states where the
> timer loses context at runtime and therefore can always be used as a high
> resolution clockevent device.
>
> In order to fix the C3STOP issue in a way compliant with how real HW
> works, this patch adds a boolean property to the arch timer bindings
> to define if the arch timer is managed by an always-on power domain.
>
> This power domain is present on all ARM platforms to date, and manages
> HW that must not be turned off, whatever the state of other HW
> components (eg power controller). On platforms with no power management
> capabilities, it is the only power domain present, which encompasses
> and manages power supply for all HW components in the system.
>
> If the timer is powered by the always-on power domain, the always-on
> property must be present in the bindings which means that the timer cannot
> be shutdown at runtime, so it is not a C3STOP clockevent device.
> If the timer binding does not contain the always-on property, the timer is
> assumed to be power-gateable, hence it must be defined as a C3STOP
> clockevent device.
>
> Cc: Daniel Lezcano <daniel.lezcano@linaro•org>
> Cc: Magnus Damm <damm@opensource•se>
> Cc: Marc Carino <marc.ceeeee@gmail•com>
> Cc: Mark Rutland <mark.rutland@arm•com>
> Acked-by: Marc Zyngier <marc.zyngier@arm•com>
> Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm•com>
> ---
Applied as 3.15 fix.
Thanks
-- Daniel
--
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prev parent reply other threads:[~2014-04-15 16:57 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-04-08 9:04 [PATCH] driver: clocksource: fix age-old arch timer C3STOP detection issue Lorenzo Pieralisi
2014-04-08 9:19 ` Marc Zyngier
2014-04-08 19:01 ` Rob Herring
2014-04-15 16:57 ` Daniel Lezcano [this message]
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