[PATCH v6] ARM: vfp: Always save VFP state in vfp_pm_suspend on UP

From: Colin Cross
Date: Mon Jul 16 2012 - 14:17:27 EST

vfp_pm_suspend should save the VFP state in suspend after
any lazy context switch. If it only saves when the VFP is enabled,
the state can get lost when, on a UP system:
Thread 1 uses the VFP
Context switch occurs to thread 2, VFP is disabled but the
VFP context is not saved
Thread 2 initiates suspend
vfp_pm_suspend is called with the VFP disabled, and the unsaved
VFP context of Thread 1 in the registers

Modify vfp_pm_suspend to save the VFP context whenever
vfp_current_hw_state is not NULL.

Includes a fix from Ido Yariv <ido@xxxxxxxxxx>, who pointed out that on
SMP systems, the state pointer can be pointing to a freed task struct if
a task exited on another cpu, fixed by using #ifdef CONFIG_SMP in the
new if clause.

Cc: Russell King <linux@xxxxxxxxxxxxxxxx>
Cc: Barry Song <bs14@xxxxxxx>
Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Ido Yariv <ido@xxxxxxxxxx>
Cc: Daniel Drake <dsd@xxxxxxxxxx>
Cc: Will Deacon <will.deacon@xxxxxxx>
Signed-off-by: Colin Cross <ccross@xxxxxxxxxxx>
arch/arm/vfp/vfpmodule.c | 6 ++++++
1 files changed, 6 insertions(+), 0 deletions(-)

diff --git a/arch/arm/vfp/vfpmodule.c b/arch/arm/vfp/vfpmodule.c
index 58696192..ce55f05 100644
--- a/arch/arm/vfp/vfpmodule.c
+++ b/arch/arm/vfp/vfpmodule.c
@@ -457,6 +457,12 @@ static int vfp_pm_suspend(void)

/* disable, just in case */
fmxr(FPEXC, fmrx(FPEXC) & ~FPEXC_EN);
+ } else if (vfp_current_hw_state[ti->cpu]) {
+#ifndef CONFIG_SMP
+ fmxr(FPEXC, fpexc | FPEXC_EN);
+ vfp_save_state(vfp_current_hw_state[ti->cpu], fpexc);
+ fmxr(FPEXC, fpexc);

/* clear any information we had about last context state */

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