Messages in this thread Patch in this message | | | From | Chris Metcalf <> | Date | Thu, 29 Mar 2012 15:57:18 -0400 | Subject | [PATCH] arch/tile: add "nop" after "nap" to help GX idle power draw |
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This avoids the hardware istream prefetcher doing unnecessary work.
Signed-off-by: Chris Metcalf <cmetcalf@tilera.com> --- arch/tile/kernel/entry.S | 2 ++ arch/tile/kernel/smp.c | 2 +- 2 files changed, 3 insertions(+), 1 deletions(-)
diff --git a/arch/tile/kernel/entry.S b/arch/tile/kernel/entry.S index f8d6155..133c4b5 100644 --- a/arch/tile/kernel/entry.S +++ b/arch/tile/kernel/entry.S @@ -85,6 +85,7 @@ STD_ENTRY(cpu_idle_on_new_stack) /* Loop forever on a nap during SMP boot. */ STD_ENTRY(smp_nap) nap + nop /* avoid provoking the icache prefetch with a jump */ j smp_nap /* we are not architecturally guaranteed not to exit nap */ jrp lr /* clue in the backtracer */ STD_ENDPROC(smp_nap) @@ -106,5 +107,6 @@ STD_ENTRY(_cpu_idle) .global _cpu_idle_nap _cpu_idle_nap: nap + nop /* avoid provoking the icache prefetch with a jump */ jrp lr STD_ENDPROC(_cpu_idle) diff --git a/arch/tile/kernel/smp.c b/arch/tile/kernel/smp.c index 7579607..f86887a 100644 --- a/arch/tile/kernel/smp.c +++ b/arch/tile/kernel/smp.c @@ -122,7 +122,7 @@ static void smp_stop_cpu_interrupt(void) set_cpu_online(smp_processor_id(), 0); arch_local_irq_disable_all(); for (;;) - asm("nap"); + asm("nap; nop"); } /* This function calls the 'stop' function on all other CPUs in the system. */ -- 1.6.5.2
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