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

From: Catalin Marinas <catalin.marinas@arm.com>
To: Russell King - ARM Linux <linux@arm.linux.org.uk>
Cc: Tero Kristo <tero.kristo@nokia.com>,
	Dave Estes <cestes@quicinc.com>,
	linux-omap@vger.kernel.org, linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 1/2] ARM: Implemented support for VFP PM context saving
Date: Tue, 24 Nov 2009 13:20:26 +0000	[thread overview]
Message-ID: <1259068826.13956.22.camel@pc1117.cambridge.arm.com> (raw)
In-Reply-To: <20091124114836.GA10510@n2100.arm.linux.org.uk>

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=commit;h=88984c9b2d69c222ee1e2afc948ca73f597d40ff

[ARM] vfp: Add additional vfp interfaces
https://www.codeaurora.org/gitweb/quic/le/?p=kernel/msm.git;a=commit;h=393e4bfaaf79377d29cd6bb2228f87601aeca668

-- 
Catalin