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Commit 8c92ba6c authored by Chris Metcalf's avatar Chris Metcalf
Browse files

arch/tile: add "nop" after "nap" to help GX idle power draw 



This avoids the hardware istream prefetcher doing unnecessary work.

Signed-off-by: default avatarChris Metcalf <cmetcalf@tilera.com>
parent bfffe79b

arch/tile/kernel/entry.S

+2 −0
Original line number Diff line number Diff line
@@ -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)

arch/tile/kernel/smp.c

+1 −1
Original line number Diff line number Diff line
@@ -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. */