From 8c92ba6c327ee5089dec1e92eaa82927bee63d6d Mon Sep 17 00:00:00 2001 From: Chris Metcalf Date: Thu, 29 Mar 2012 15:57:18 -0400 Subject: arch/tile: add "nop" after "nap" to help GX idle power draw This avoids the hardware istream prefetcher doing unnecessary work. Signed-off-by: Chris Metcalf diff --git a/arch/tile/kernel/entry.S b/arch/tile/kernel/entry.S index 431e9ae..ec91568 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) @@ -105,5 +106,6 @@ 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 a44e103..7b6df8c 100644 --- a/arch/tile/kernel/smp.c +++ b/arch/tile/kernel/smp.c @@ -103,7 +103,7 @@ 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. */ -- cgit v0.10.2