powerpc/powernv: Make it possible to skip the IRQHAPPENED check in power7_nap()

To support split core we need to be able to force all secondaries into
nap, so the core can detect they are idle and do an unsplit.

Currently power7_nap() will return without napping if there is an irq
pending. We want to ignore the pending irq and nap anyway, we will deal
with the interrupt later.
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/include/asm/processor.h

@@ -449,7 +449,7 @@ extern unsigned long cpuidle_disable;
 enum idle_boot_override {IDLE_NO_OVERRIDE = 0, IDLE_POWERSAVE_OFF};
 
 extern int powersave_nap;	/* set if nap mode can be used in idle loop */
-extern void power7_nap(void);
+extern void power7_nap(int check_irq);
 extern void power7_sleep(void);
 extern void flush_instruction_cache(void);
 extern void hard_reset_now(void);

arch/powerpc/kernel/idle_power7.S

@@ -39,6 +39,10 @@
  * Pass requested state in r3:
  * 	0 - nap
  * 	1 - sleep
+ *
+ * To check IRQ_HAPPENED in r4
+ * 	0 - don't check
+ * 	1 - check
  */
 _GLOBAL(power7_powersave_common)
 	/* Use r3 to pass state nap/sleep/winkle */
@@ -71,6 +75,8 @@ _GLOBAL(power7_powersave_common)
 	lbz	r0,PACAIRQHAPPENED(r13)
 	cmpwi	cr0,r0,0
 	beq	1f
+	cmpwi	cr0,r4,0
+	beq	1f
 	addi	r1,r1,INT_FRAME_SIZE
 	ld	r0,16(r1)
 	mtlr	r0
@@ -114,15 +120,18 @@ _GLOBAL(power7_idle)
 	lwz	r4,ADDROFF(powersave_nap)(r3)
 	cmpwi	0,r4,0
 	beqlr
+	li	r3, 1
 	/* fall through */
 
 _GLOBAL(power7_nap)
+	mr	r4,r3
 	li	r3,0
 	b	power7_powersave_common
 	/* No return */
 
 _GLOBAL(power7_sleep)
 	li	r3,1
+	li	r4,0
 	b	power7_powersave_common
 	/* No return */
 

arch/powerpc/platforms/powernv/smp.c

@@ -159,7 +159,7 @@ static void pnv_smp_cpu_kill_self(void)
 	mtspr(SPRN_LPCR, mfspr(SPRN_LPCR) & ~(u64)LPCR_PECE1);
 	while (!generic_check_cpu_restart(cpu)) {
 		ppc64_runlatch_off();
-		power7_nap();
+		power7_nap(1);
 		ppc64_runlatch_on();
 		if (!generic_check_cpu_restart(cpu)) {
 			DBG("CPU%d Unexpected exit while offline !\n", cpu);