ppc64: Fix occasional crash at boot in OF interface

@@ -570,11 +570,10 @@
 	 * of all registers that it saves.  We therefore save those registers
 	 * PROM might touch to the stack.  (r0, r3-r13 are caller saved)
    	 */
-	SAVE_8GPRS(2, r1)		/* Save the TOC & incoming param(s) */
-	SAVE_GPR(13, r1)		/* Save paca */
-	SAVE_8GPRS(14, r1)		/* Save the non-volatiles */
-	SAVE_10GPRS(22, r1)		/* ditto */
-
+	SAVE_8GPRS(2, r1)
+	SAVE_GPR(13, r1)
+	SAVE_8GPRS(14, r1)
+	SAVE_10GPRS(22, r1)
 	mfcr	r4
 	std	r4,_CCR(r1)
 	mfctr	r5

@@ -592,20 +591,16 @@
 	mfmsr	r11
 	std	r11,_MSR(r1)
 
-	/* Unfortunatly, the stack pointer is also clobbered, so it is saved
-	 * in the SPRG2 which allows us to restore our original state after
-	 * PROM returns.
-         */
-	mtspr	SPRG2,r1
-
-        /* put a relocation offset into r3 */
+	/* Get the PROM entrypoint */
         bl      .reloc_offset
 	LOADADDR(r12,prom)
 	sub	r12,r12,r3
-	ld	r12,PROMENTRY(r12)	/* get the prom->entry value */
+	ld	r12,PROMENTRY(r12)
 	mtlr	r12
 
-        mfmsr   r11			/* grab the current MSR */
+	/* Switch MSR to 32 bits mode
+	 */
+        mfmsr   r11
         li      r12,1
         rldicr  r12,r12,MSR_SF_LG,(63-MSR_SF_LG)
         andc    r11,r11,r12

@@ -615,22 +610,25 @@
         mtmsrd  r11
         isync
 
-	REST_8GPRS(2, r1)		/* Restore the TOC & param(s) */
-	REST_GPR(13, r1)		/* Restore paca */
-	REST_8GPRS(14, r1)		/* Restore the non-volatiles */
-	REST_10GPRS(22, r1)		/* ditto */
-	blrl				/* Entering PROM here... */
-
-	mfspr	r1,SPRG2		/* Restore the stack pointer */
-	ld	r6,_MSR(r1)		/* Restore the MSR */
-	mtmsrd	r6
+	/* Restore arguments & enter PROM here... */
+	ld	r3,GPR3(r1)
+	blrl
+
+	/* Just make sure that r1 top 32 bits didn't get
+	 * corrupt by OF
+	 */
+	rldicl	r1,r1,0,32
+
+	/* Restore the MSR (back to 64 bits) */
+	ld	r0,_MSR(r1)
+	mtmsrd	r0
         isync
 
-	REST_GPR(2, r1)			/* Restore the TOC */
-	REST_GPR(13, r1)		/* Restore paca */
-	REST_8GPRS(14, r1)		/* Restore the non-volatiles */
-	REST_10GPRS(22, r1)		/* ditto */
-
+	/* Restore other registers */
+	REST_GPR(2, r1)
+	REST_GPR(13, r1)
+	REST_8GPRS(14, r1)
+	REST_10GPRS(22, r1)
 	ld	r4,_CCR(r1)
 	mtcr	r4
 	ld	r5,_CTR(r1)

@@ -645,9 +643,10 @@
 	mtsrr0	r9
 	ld	r10,_SRR1(r1)
 	mtsrr1	r10
+	
         addi	r1,r1,PROM_FRAME_SIZE
-	ld	r0,16(r1)		/* get return address */
-
+	ld	r0,16(r1)
 	mtlr    r0
-        blr				/* return to caller */
+        blr
+	
 #endif	/* defined(CONFIG_PPC_PSERIES) */