[PATCH 1/2] ARM: Implemented support for VFP PM context saving

[Tero.Kristo at nokia.com]

>-----Original Message-----
>From: ext Catalin Marinas [mailto:catalin.marinas at arm.com] 
>Sent: 24 November, 2009 15:20
>To: Russell King - ARM Linux
>Cc: Kristo Tero (Nokia-D/Tampere); linux-omap at vger.kernel.org; 
>linux-arm-kernel at lists.infradead.org; Dave Estes
>Subject: Re: [PATCH 1/2] ARM: Implemented support for VFP PM 
>context saving
>
>On Tue, 2009-11-24 at 11:48 +0000, Russell King - ARM Linux wrote:
>> On Tue, Nov 24, 2009 at 12:37:03PM +0200, Tero Kristo wrote:
>> > In some ARM architectures, like OMAP3, the VFP context can 
>be lost during
>> > dynamic sleep cycle. For this purpose, there is now a function
>> > vfp_pm_save_context() that should be called before the VFP 
>is assumed to
>> > lose context. Next VFP trap will then restore context 
>automatically.
>> >
>> > We need to have the last_VFP_context[cpu] cleared after 
>the save in idle,
>> > else the restore would fail to restore when it sees that 
>the last_VFP_context
>> > is same as the current threads vfp_state. This happens 
>when the same
>> > process/thread traps an exception post idle.
>> >
>> > Main work for this patch was done by Peter and Rajendra. 
>Some cleanup and
>> > optimization by Tero.
>> 
>> Why not re-use vfp_pm_suspend() ?  Haven't you shown that 
>vfp_pm_suspend
>> may be buggy since it doesn't save in the VFP-disabled case?
>BTW, the two patches below were mentioned to me some time ago but I
>haven't got the time to look at them:
>
>[ARM] vfp: Fix bug in vfp_pm_suspend
>https://www.codeaurora.org/gitweb/quic/le/?p=kernel/msm.git;a=c
>ommit;h=88984c9b2d69c222ee1e2afc948ca73f597d40ff
>
>[ARM] vfp: Add additional vfp interfaces
>https://www.codeaurora.org/gitweb/quic/le/?p=kernel/msm.git;a=c
>ommit;h=393e4bfaaf79377d29cd6bb2228f87601aeca668

These look pretty much like the same thing we have attempted on the omap3 patches, I could try these out and check if they work for omap3 also. They fix the potentially broken suspend also.

-Tero