powerpc/book3s: Fix endianess issue for HMI handling on napping cpus.

(NOTE: This patch depends on upstream HMI handling patchset at
 https://lists.ozlabs.org/pipermail/linuxppc-dev/2014-July/119731.html)

The current HMI handling on napping cpus does not take care of endianess
issue. On LE host kernel when we wake up from nap due to HMI interrupt we
would checkstop while jumping into opal call. There is a similar issue in
case of fast sleep wakeup where the code invokes opal_resync_tb opal call
without handling LE issue. This patch fixes that as well.

With this patch applied, HMIs handling on LE host kernel works fine.
Signed-off-by: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/kernel/idle_power7.S

@@ -135,6 +135,39 @@ _GLOBAL(power7_sleep)
 	b	power7_powersave_common
 	/* No return */
 
+/*
+ * Make opal call in realmode. This is a generic function to be called
+ * from realmode from reset vector. It handles endianess.
+ *
+ * r13 - paca pointer
+ * r1  - stack pointer
+ * r3  - opal token
+ */
+opal_call_realmode:
+	mflr	r12
+	std	r12,_LINK(r1)
+	ld	r2,PACATOC(r13)
+	/* Set opal return address */
+	LOAD_REG_ADDR(r0,return_from_opal_call)
+	mtlr	r0
+	/* Handle endian-ness */
+	li	r0,MSR_LE
+	mfmsr	r12
+	andc	r12,r12,r0
+	mtspr	SPRN_HSRR1,r12
+	mr	r0,r3			/* Move opal token to r0 */
+	LOAD_REG_ADDR(r11,opal)
+	ld	r12,8(r11)
+	ld	r2,0(r11)
+	mtspr	SPRN_HSRR0,r12
+	hrfid
+
+return_from_opal_call:
+	FIXUP_ENDIAN
+	ld	r0,_LINK(r1)
+	mtlr	r0
+	blr
+
 #define CHECK_HMI_INTERRUPT						\
 	mfspr	r0,SPRN_SRR1;						\
 BEGIN_FTR_SECTION_NESTED(66);						\
@@ -148,12 +181,8 @@ ALT_FTR_SECTION_END_NESTED_IFSET(CPU_FTR_ARCH_207S, 66);		\
 	ld	r2,PACATOC(r13);					\
 	ld	r1,PACAR1(r13);						\
 	std	r3,ORIG_GPR3(r1);	/* Save original r3 */		\
-	li	r0,OPAL_HANDLE_HMI;					\
-	LOAD_REG_ADDR(r11,opal);					\
-	ld	r12,8(r11);						\
-	ld	r2,0(r11);						\
-	mtctr	r12;							\
-	bctrl;								\
+	li	r3,OPAL_HANDLE_HMI;	/* Pass opal token argument*/	\
+	bl	opal_call_realmode;					\
 	ld	r3,ORIG_GPR3(r1);	/* Restore original r3 */	\
 20:	nop;
 
@@ -166,12 +195,8 @@ BEGIN_FTR_SECTION
 	CHECK_HMI_INTERRUPT
 END_FTR_SECTION_IFSET(CPU_FTR_HVMODE)
 	/* Time base re-sync */
-	li	r0,OPAL_RESYNC_TIMEBASE
-	LOAD_REG_ADDR(r11,opal);
-	ld	r12,8(r11);
-	ld	r2,0(r11);
-	mtctr	r12
-	bctrl
+	li	r3,OPAL_RESYNC_TIMEBASE
+	bl	opal_call_realmode;
 
 	/* TODO: Check r3 for failure */