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

On Mon, Feb 14, 2011 at 3:42 AM, Catalin Marinas
[off-list ref] wrote:

On Sun, 2011-02-13 at 23:13 +0000, Colin Cross wrote:

quoted

vfp_pm_suspend should save the VFP state any time there is
a last_VFP_context. ?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 to allow lazy save and restore
? ?Thread 2 initiates suspend
? ?vfp_pm_suspend is called with the VFP disabled, but the
? ? ? context has not been saved.

At this point is it guaranteed that the thread won't migrate to another
CPU? If not, we should use get/put_cpu.

Yes, VFP suspend is implemented with a sysdev, which is suspended
after disable_nonboot_cpus.

quoted

--- a/arch/arm/vfp/vfpmodule.c
+++ b/arch/arm/vfp/vfpmodule.c

@@ -415,13 +415,12 @@ static int vfp_pm_suspend(struct sys_device *dev, pm_message_t state)

? ? ? ? struct thread_info *ti = current_thread_info();
? ? ? ? u32 fpexc = fmrx(FPEXC);

- ? ? ? /* if vfp is on, then save state for resumption */
- ? ? ? if (fpexc & FPEXC_EN) {
+ ? ? ? /* save state for resume */
+ ? ? ? if (last_VFP_context[ti->cpu]) {
? ? ? ? ? ? ? ? printk(KERN_DEBUG "%s: saving vfp state\n", __func__);
- ? ? ? ? ? ? ? vfp_save_state(&ti->vfpstate, fpexc);
-
- ? ? ? ? ? ? ? /* disable, just in case */
- ? ? ? ? ? ? ? fmxr(FPEXC, fmrx(FPEXC) & ~FPEXC_EN);
+ ? ? ? ? ? ? ? fmxr(FPEXC, fpexc | FPEXC_EN);
+ ? ? ? ? ? ? ? vfp_save_state(last_VFP_context[ti->cpu], fpexc);
+ ? ? ? ? ? ? ? fmxr(FPEXC, fpexc & ~FPEXC_EN);
? ? ? ? }

We may want to set the last_VFP_context to NULL so that after resuming
(to the same thread) we force the VFP reload from the vfpstate
structure. The vfp_support_entry code ignores the reloading if the
last_VFP_context is the same as vfpstate.

Right, will fix.