From: nicolas.ferre@atmel•com (Nicolas Ferre)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH 5/7] at91 : fix dirty hack for the selfrefresh function
Date: Thu, 12 Jan 2012 15:41:29 +0100 [thread overview]
Message-ID: <4F0EF119.3000605@atmel.com> (raw)
In-Reply-To: <20120111194334.GF1068@n2100.arm.linux.org.uk>
On 01/11/2012 08:43 PM, Russell King - ARM Linux :
[..]
> On the other hand, we have another DWB in cpu_arm926_do_idle itself.
>
> Whether any of this matters depends on _why_ that DWB is in the AT91
> code itself - is it something that needs to be done before placing the
> SDRAM into self-refresh mode, or is it being done merely because the
> ARM926 docs say that a DWB is needed before WFI?
We have two cases here:
For the venerable at91rm9200: DWB is needed before putting SDRAM into
self-refresh because any subsequent access to SDRAM will force it to
resume from self-refresh state. Of course for this case, it is important
to make sure that no access to SDRAM is made before the
wait-for-interrupt instruction.
For all other SAM9 SoCs: no additional DWB is needed because RAM
controller manages self-refresh state even if accesses are still done to
the memory.
> If the latter, it can be dispensed with because the CPU specific code
> is already doing that.
Yes, exactly, but only for SAM9, not for RM9200.
> In any case, I think we need someone to speak up who knows this bit of
> the AT91 code, and it needs fixing so that it's less reliant on luck -
> otherwise cleanups could introduce some rather horrible bugs.
Ok, Daniel, tell me how I can help you. Is there any information that is
missing on your side?
BTW, you may save time by skipping all CAP9 related changes (and remove
the code): We shall remove its support in kernel for 3.4 release:
https://lkml.org/lkml/2012/1/6/161
Best regards,
--
Nicolas Ferre
next prev parent reply other threads:[~2012-01-12 14:41 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-01-11 14:55 [PATCH 0/7] at91 : pm.h cleanups Daniel Lezcano
2012-01-11 14:55 ` [PATCH 1/7] at91 : coding style fixes Daniel Lezcano
2012-01-11 14:55 ` [PATCH 2/7] at91 : declare header name Daniel Lezcano
2012-01-11 14:55 ` [PATCH 3/7] at91 : group headers inclusion for the memory controller Daniel Lezcano
2012-01-11 14:55 ` [PATCH 4/7] at91 : convert pm.h macros to static inline functions Daniel Lezcano
2012-01-11 14:55 ` [PATCH 5/7] at91 : fix dirty hack for the selfrefresh function Daniel Lezcano
2012-01-11 15:10 ` Arnd Bergmann
2012-01-11 16:55 ` Russell King - ARM Linux
2012-01-11 18:27 ` Arnd Bergmann
2012-01-11 19:43 ` Russell King - ARM Linux
2012-01-12 14:41 ` Nicolas Ferre [this message]
2012-01-12 19:36 ` Russell King - ARM Linux
2012-01-13 0:38 ` Rob Lee
2012-01-13 9:29 ` Daniel Lezcano
2012-01-13 10:22 ` Russell King - ARM Linux
2012-01-13 15:48 ` Arnd Bergmann
2012-01-13 17:25 ` Rob Lee
2012-01-11 14:55 ` [PATCH 6/7] at91 : group selfrefresh functions Daniel Lezcano
2012-01-11 16:56 ` Russell King - ARM Linux
2012-01-11 14:55 ` [PATCH 7/7] at91 : fix compilation warning Daniel Lezcano
2012-01-11 15:23 ` [PATCH 0/7] at91 : pm.h cleanups Arnd Bergmann
2012-01-11 16:29 ` Daniel Lezcano
2012-01-23 6:29 ` Jean-Christophe PLAGNIOL-VILLARD
2012-01-11 16:57 ` Russell King - ARM Linux
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