powerpc/64s: Fix PACA_IRQ_HARD_DIS accounting in idle_power4()

When idle_power4() hard disables interrupts then finds a soft pending
interrupt, it returns with interrupts hard disabled but without
PACA_IRQ_HARD_DIS set. Commit 9b81c021 ("powerpc/64s: make
PACA_IRQ_HARD_DIS track MSR[EE] closely") added a warning for that
condition (since disabled).

Fix this by adding the PACA_IRQ_HARD_DIS for that case.
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/kernel/idle_power4.S

@@ -32,6 +32,8 @@ END_FTR_SECTION_IFCLR(CPU_FTR_CAN_NAP)
 	cmpwi	0,r4,0
 	beqlr
 
+	/* This sequence is similar to prep_irq_for_idle() */
+
 	/* Hard disable interrupts */
 	mfmsr	r7
 	rldicl	r0,r7,48,1
@@ -41,10 +43,15 @@ END_FTR_SECTION_IFCLR(CPU_FTR_CAN_NAP)
 	/* Check if something happened while soft-disabled */
 	lbz	r0,PACAIRQHAPPENED(r13)
 	cmpwi	cr0,r0,0
-	bnelr
+	bne-	2f
 
-	/* Soft-enable interrupts */
+	/*
+	 * Soft-enable interrupts. This will make power4_fixup_nap return
+	 * to our caller with interrupts enabled (soft and hard). The caller
+	 * can cope with either interrupts disabled or enabled upon return.
+	 */
 #ifdef CONFIG_TRACE_IRQFLAGS
+	/* Tell the tracer interrupts are on, because idle responds to them. */
 	mflr	r0
 	std	r0,16(r1)
 	stdu    r1,-128(r1)
@@ -73,3 +80,8 @@ END_FTR_SECTION_IFSET(CPU_FTR_ALTIVEC)
 	isync
 	b	1b
 
+2:	/* Return if an interrupt had happened while soft disabled */
+	/* Set the HARD_DIS flag because interrupts are now hard disabled */
+	ori	r0,r0,PACA_IRQ_HARD_DIS
+	stb	r0,PACAIRQHAPPENED(r13)
+	blr