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ARM: vfp: fix vfp_sync_state()

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The more I look at vfp_sync_state(), the more I believe it's trying
to do its job in a really obscure way.

Essentially, last_VFP_context[] tracks who owns the state in the VFP
hardware.  If last_VFP_context[] is the context for the thread which
we're interested in, then the VFP hardware has context which is not
saved in the software state - so we need to bring the software state
up to date.

If last_VFP_context[] is for some other thread, we really don't care
what state the VFP hardware is in; it doesn't contain any information
pertinent to the thread we're trying to deal with - so don't touch
the hardware.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This commit is contained in:
Russell King 2010-02-06 11:27:45 +00:00
parent 462f39a8c7
commit 54cb3dbb4a
1 changed files with 16 additions and 20 deletions
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36
arch/arm/vfp/vfpmodule.c
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@ -444,32 +444,28 @@ void vfp_sync_state(struct thread_info *thread)
void vfp_sync_state(struct thread_info *thread)
{
unsigned int cpu = get_cpu();
u32 fpexc = fmrx(FPEXC);
/*
* If VFP is enabled, the previous state was already saved and
* last_VFP_context updated.
* If the thread we're interested in is the current owner of the
* hardware VFP state, then we need to save its state.
*/
if (fpexc & FPEXC_EN)
goto out;
if (last_VFP_context[cpu] == &thread->vfpstate) {
u32 fpexc = fmrx(FPEXC);
if (!last_VFP_context[cpu])
goto out;
/*
* Save the last VFP state on this CPU.
*/
fmxr(FPEXC, fpexc | FPEXC_EN);
vfp_save_state(&thread->vfpstate, fpexc | FPEXC_EN);
fmxr(FPEXC, fpexc & ~FPEXC_EN);
/*
* Save the last VFP state on this CPU.
*/
fmxr(FPEXC, fpexc | FPEXC_EN);
vfp_save_state(last_VFP_context[cpu], fpexc);
fmxr(FPEXC, fpexc);
/*
* Set the context to NULL to force a reload the next time
* the thread uses the VFP.
*/
last_VFP_context[cpu] = NULL;
}
/*
* Set the context to NULL to force a reload the next time the thread
* uses the VFP.
*/
last_VFP_context[cpu] = NULL;
out:
put_cpu();
}
#endif