powerpc/book3e: Don't re-trigger decrementer on lazy irq restore

The decrementer on BookE acts as a level interrupt and doesn't
need to be re-triggered when going negative. It doesn't go
negative anyways (unless programmed to auto-reload with a
negative value) as it stops when reaching 0.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

1 files changed, 9 insertions, 0 deletions

diff --git a/arch/powerpc/kernel/irq.c b/arch/powerpc/kernel/irq.c
index 77be3d058a65..fa6f38525801 100644
--- a/arch/powerpc/kernel/irq.c
+++ b/arch/powerpc/kernel/irq.c
@@ -159,8 +159,17 @@ notrace void raw_local_irq_restore(unsigned long en)
          * use local_paca instead of get_paca() to avoid preemption checking.
          */
         local_paca->hard_enabled = en;
+
+#ifndef CONFIG_BOOKE
+        /* On server, re-trigger the decrementer if it went negative since
+         * some processors only trigger on edge transitions of the sign bit.
+         *
+         * BookE has a level sensitive decrementer (latches in TSR) so we
+         * don't need that
+         */
         if ((int)mfspr(SPRN_DEC) < 0)
                 mtspr(SPRN_DEC, 1);
+#endif /* CONFIG_BOOKE */
 
         /*
          * Force the delivery of pending soft-disabled interrupts on PS3.