From: linux@arm.linux.org.uk (Russell King - ARM Linux)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH 3/4] at91 : remove wait_for_interrupt definition
Date: Wed, 25 Jan 2012 00:18:58 +0000 [thread overview]
Message-ID: <20120125001858.GD12326@n2100.arm.linux.org.uk> (raw)
In-Reply-To: <1327449368-29917-3-git-send-email-daniel.lezcano@linaro.org>
On Wed, Jan 25, 2012 at 12:56:07AM +0100, Daniel Lezcano wrote:
> All the "wait_for_interrupt" definition are aliases to cpu_do_idle.
> Only the rm9200 has an asm routine to switch to wfi. But the cpu_do_idle
> for this platform has exactly the same asm routine.
>
> arch/arm/mm/proc-arm920.S
> ...
> ENTRY(cpu_arm920_do_idle)
> mcr p15, 0, r0, c7, c0, 4 @ Wait for interrupt
> ...
>
> Then it is safe to invoke cpu_do_idle for this platform.
No it is not.
Please read Nicolas' post:
http://lists.arm.linux.org.uk/lurker/message/20120112.144129.827ae490.en.html
and think about what "DWB is needed before putting SDRAM into self-refresh
because any subsequent access to SDRAM will force it to resume from
self-refresh state" means.
Consider that if you _branch_ somewhere else, you _could_ cause a cache
line fetch, which will have to come from SDRAM.
>From Nicolas' post, it's pretty clear to me that the AT91RM9200 requires
carefully crafted assembly which can't be separated in this way to work,
which I mostly supplied in this mail:
http://lists.arm.linux.org.uk/lurker/message/20120109.144443.3626e5a6.en.html
next prev parent reply other threads:[~2012-01-25 0:18 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-01-24 23:56 [PATCH 1/4] at91 : coding style fixes Daniel Lezcano
2012-01-24 23:56 ` [PATCH 2/4] at91 : declare header name Daniel Lezcano
2012-01-24 23:56 ` [PATCH 3/4] at91 : remove wait_for_interrupt definition Daniel Lezcano
2012-01-25 0:18 ` Russell King - ARM Linux [this message]
2012-01-25 14:39 ` Daniel Lezcano
2012-02-27 12:50 ` Russell King - ARM Linux
2012-02-27 13:07 ` Daniel Lezcano
2012-02-27 14:52 ` Rob Lee
2012-01-24 23:56 ` [PATCH 4/4] at91 : implement the standby function for pm/cpuidle Daniel Lezcano
2012-01-26 16:18 ` at91: pm.h cleanup (was: [PATCH 1/4] at91 : coding style fixes) Nicolas Ferre
2012-01-26 20:33 ` Russell King - ARM Linux
2012-01-26 23:34 ` Russell King - ARM Linux
2012-01-27 9:43 ` at91: pm.h cleanup Nicolas Ferre
-- strict thread matches above, loose matches on Subject: below --
2012-01-17 23:40 [PATCH 0/4] at91 : cleanup pm.h Daniel Lezcano
2012-01-17 23:40 ` [PATCH 3/4] at91 : remove wait_for_interrupt definition Daniel Lezcano
2012-01-18 21:53 ` Ryan Mallon
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