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Commit 54cb3dbb authored by Russell King's avatar Russell King
Browse files

ARM: vfp: fix vfp_sync_state() 



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: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
parent 462f39a8

arch/arm/vfp/vfpmodule.c

+16 −20
Original line number Diff line number Diff line
@@ -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])

		goto out;

	if (last_VFP_context[cpu] == &thread->vfpstate) {

		u32 fpexc = fmrx(FPEXC);



		/*

		 * Save the last VFP state on this CPU.

		 */

		fmxr(FPEXC, fpexc | FPEXC_EN);

	vfp_save_state(last_VFP_context[cpu], fpexc);

	fmxr(FPEXC, fpexc);

		vfp_save_state(&thread->vfpstate, fpexc | FPEXC_EN);

		fmxr(FPEXC, fpexc & ~FPEXC_EN);



		/*

	 * Set the context to NULL to force a reload the next time the thread

	 * uses the VFP.

		 * 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