[RFC/PATCH] powernv: Handle wakeup from stop due to SRESET

["Gautham R. Shenoy" <ego@linux.vnet.ibm.com>]

From: "Gautham R. Shenoy" <ego@linux.vnet.ibm.com>

The existing code doesn't handle the case when CPU which was in a
hardware-idle state (nap,sleep,winkle on POWER8 and various stop
states on POWER9) gets woken up due to a System Reset interrupt.

This patch checks if the CPU was woken up due to System Reset, in
which case, after restoring the required hardware state, it jumps to
the system reset handler.

Signed-off-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
---
 arch/powerpc/kernel/idle_book3s.S | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/arch/powerpc/kernel/idle_book3s.S b/arch/powerpc/kernel/idle_book3s.S
index 72dac0b..0098879 100644
--- a/arch/powerpc/kernel/idle_book3s.S
+++ b/arch/powerpc/kernel/idle_book3s.S
@@ -353,6 +353,18 @@ ALT_FTR_SECTION_END_NESTED_IFSET(CPU_FTR_ARCH_207S, 66);		\
 	ld	r3,ORIG_GPR3(r1);	/* Restore original r3 */	\
 20:	nop;
 
+#define CHECK_SRESET_INTERRUPT                                          \
+BEGIN_FTR_SECTION_NESTED(67);						\
+	mfspr	r0,SPRN_SRR1;						\
+	rlwinm	r0,r0,45-31,0xf; /* Extract wake reason field (P8,9) */ \
+	cmpwi	r0,0x4;		  /* System Reset ? 	*/		\
+	bne	21f;							\
+	b	system_reset_common; 					\
+	b	.; 		/* We shouldn't return here */		\
+FTR_SECTION_ELSE_NESTED(67);						\
+	nop		   ;						\
+ALT_FTR_SECTION_END_NESTED_IFSET(CPU_FTR_ARCH_207S, 67);		\
+21:	nop;
 
 /*
  * r3 - requested stop state
@@ -644,6 +656,7 @@ _GLOBAL(pnv_wakeup_loss)
 	ld	r1,PACAR1(r13)
 BEGIN_FTR_SECTION
 	CHECK_HMI_INTERRUPT
+	CHECK_SRESET_INTERRUPT
 END_FTR_SECTION_IFSET(CPU_FTR_HVMODE)
 	REST_NVGPRS(r1)
 	REST_GPR(2, r1)
@@ -666,6 +679,7 @@ _GLOBAL(pnv_wakeup_noloss)
 	bne	pnv_wakeup_loss
 BEGIN_FTR_SECTION
 	CHECK_HMI_INTERRUPT
+	CHECK_SRESET_INTERRUPT
 END_FTR_SECTION_IFSET(CPU_FTR_HVMODE)
 	ld	r1,PACAR1(r13)
 	ld	r6,_CCR(r1)
-- 
1.8.3.1