[OpenBIOS] [PATCH] ppc: use rfid when running under a CPU from the 970 family.

[Cédric Le Goater]

A recent attempt to restrict the use of rfi to 64bit cpus in qemu
broke 32bit OpenBIOS when run under a 970.

This is adding a dynamic check on the pvr to choose between rfi and
rfid. Only the 970 family is supported.

Signed-off-by: Cédric Le Goater <clg at kaod.org>
---

 Tested on qemu.

 arch/ppc/qemu/start.S |   25 +++++++++++++++++++++++--
 arch/ppc/start.S      |   25 +++++++++++++++++++++++--
 2 files changed, 46 insertions(+), 4 deletions(-)

Index: openbios.git/arch/ppc/qemu/start.S
===================================================================
--- openbios.git.orig/arch/ppc/qemu/start.S
+++ openbios.git/arch/ppc/qemu/start.S
@@ -27,6 +27,27 @@
 
 #ifdef CONFIG_PPC_64BITSUPPORT
 
+/* When running on ppc64, we cannot use rfi anymore. Let's try to
+ * catch which cpu we are running on and act accordingly. This is
+ * for 970s only.
+ */
+.macro do_rfi
+	mtsprg1	r3
+	mfpvr r3
+	rlwinm	r3,r3,16,16,31
+	cmplwi	cr1,r3,0x0039 	/* 970 CPUs */
+	beq- cr1,0f
+	cmplwi	cr1,r3,0x003C 	/* 970fx CPUs */
+	beq- cr1,0f
+	cmplwi	cr1,r3,0x0044 	/* 970mp CPUs */
+	beq- cr1,0f
+	mfsprg1	r3
+	rfi
+0:
+	mfsprg1	r3
+	rfid
+.endm
+
 /* We're trying to use the same code for the ppc32 and ppc64 handlers here.
  * On ppc32 we only save/restore the registers, C considers volatile.
  *
@@ -148,7 +169,7 @@
 	ll	r31,(35 * ULONG_SIZE)(r1) ; \
 .endif ; \
 	ll	r1,(1 * ULONG_SIZE)(r1) ;	/* restore stack at last */ \
-	rfi
+	do_rfi
 
 // PPC32
 
@@ -319,7 +340,7 @@ VECTOR( 0x800, "FPU" ):
 	ori	r3,r3,0x2000
 	mtsrr1	r3
 	mfsprg1	r3
-	RFI
+	do_rfi
 
 ILLEGAL_VECTOR( 0x900 )
 ILLEGAL_VECTOR( 0xa00 )
Index: openbios.git/arch/ppc/start.S
===================================================================
--- openbios.git.orig/arch/ppc/start.S
+++ openbios.git/arch/ppc/start.S
@@ -25,6 +25,27 @@
 #define ILLEGAL_VECTOR( v )	.org __vectors + v ; bl trap_error ;
 #define VECTOR( v, dummystr )	.org __vectors + v ; vector__##v
 
+/* When running on ppc64, we cannot use rfi anymore. Let's try to
+ * catch which cpu we are running on and act accordingly. This is
+ * for 970s only.
+ */
+.macro do_rfi
+	mtsprg1	r3
+	mfpvr r3
+	rlwinm	r3,r3,16,16,31
+	cmplwi	cr1,r3,0x0039 	/* 970 CPUs */
+	beq- cr1,0f
+	cmplwi	cr1,r3,0x003C 	/* 970fx CPUs */
+	beq- cr1,0f
+	cmplwi	cr1,r3,0x0044 	/* 970mp CPUs */
+	beq- cr1,0f
+	mfsprg1	r3
+	rfi
+0:
+	mfsprg1	r3
+	rfid
+.endm
+
 #define EXCEPTION_PREAMBLE \
 	mtsprg1	r1 ;		/* scratch */ \
 	mfsprg0	r1 ;		/* exception stack in sprg0 */ \
@@ -252,7 +273,7 @@ exception_return:
 	lwz	r11,44(r1)
 	lwz	r12,48(r1)
 	lwz	r1,4(r1)	// restore r1
-	rfi
+	do_rfi
 
 trap_error:
 	mflr	r3
@@ -287,7 +308,7 @@ VECTOR( 0x800, "FPU" ):
 	ori	r3,r3,0x2000
 	mtsrr1	r3
 	mfsprg1	r3
-	rfi
+	do_rfi
 
 ILLEGAL_VECTOR( 0x900 )
 ILLEGAL_VECTOR( 0xa00 )