powerpc: Use names rather than numbers for SPRGs (v2)

The kernel uses SPRG registers for various purposes, typically in
low level assembly code as scratch registers or to hold per-cpu
global infos such as the PACA or the current thread_info pointer.

We want to be able to easily shuffle the usage of those registers
as some implementations have specific constraints realted to some
of them, for example, some have userspace readable aliases, etc..
and the current choice isn't always the best.

This patch should not change any code generation, and replaces the
usage of SPRN_SPRGn everywhere in the kernel with a named replacement
and adds documentation next to the definition of the names as to
what those are used for on each processor family.

The only parts that still use the original numbers are bits of KVM
or suspend/resume code that just blindly needs to save/restore all
the SPRGs.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

1 files changed, 20 insertions, 20 deletions

diff --git a/arch/powerpc/kernel/head_32.S b/arch/powerpc/kernel/head_32.S
index fc2132942754..829c3fe7c5a2 100644
--- a/arch/powerpc/kernel/head_32.S
+++ b/arch/powerpc/kernel/head_32.S
@@ -244,8 +244,8 @@ __secondary_hold_acknowledge:
  * task's thread_struct.
  */
 #define EXCEPTION_PROLOG	\
-	mtspr	SPRN_SPRG0,r10;	\
-	mtspr	SPRN_SPRG1,r11;	\
+	mtspr	SPRN_SPRG_SCRATCH0,r10;	\
+	mtspr	SPRN_SPRG_SCRATCH1,r11;	\
 	mfcr	r10;		\
 	EXCEPTION_PROLOG_1;	\
 	EXCEPTION_PROLOG_2
@@ -255,7 +255,7 @@ __secondary_hold_acknowledge:
 	andi.	r11,r11,MSR_PR;	\
 	tophys(r11,r1);			/* use tophys(r1) if kernel */ \
 	beq	1f;		\
-	mfspr	r11,SPRN_SPRG3;	\
+	mfspr	r11,SPRN_SPRG_THREAD;	\
 	lwz	r11,THREAD_INFO-THREAD(r11);	\
 	addi	r11,r11,THREAD_SIZE;	\
 	tophys(r11,r11);	\
@@ -267,9 +267,9 @@ __secondary_hold_acknowledge:
 	stw	r10,_CCR(r11);		/* save registers */ \
 	stw	r12,GPR12(r11);	\
 	stw	r9,GPR9(r11);	\
-	mfspr	r10,SPRN_SPRG0;	\
+	mfspr	r10,SPRN_SPRG_SCRATCH0;	\
 	stw	r10,GPR10(r11);	\
-	mfspr	r12,SPRN_SPRG1;	\
+	mfspr	r12,SPRN_SPRG_SCRATCH1;	\
 	stw	r12,GPR11(r11);	\
 	mflr	r10;		\
 	stw	r10,_LINK(r11);	\
@@ -355,11 +355,11 @@ i##n:								\
  *	-- paulus.
  */
 	. = 0x200
-	mtspr	SPRN_SPRG0,r10
-	mtspr	SPRN_SPRG1,r11
+	mtspr	SPRN_SPRG_SCRATCH0,r10
+	mtspr	SPRN_SPRG_SCRATCH1,r11
 	mfcr	r10
 #ifdef CONFIG_PPC_CHRP
-	mfspr	r11,SPRN_SPRG2
+	mfspr	r11,SPRN_SPRG_RTAS
 	cmpwi	0,r11,0
 	bne	7f
 #endif /* CONFIG_PPC_CHRP */
@@ -367,7 +367,7 @@ i##n:								\
 7:	EXCEPTION_PROLOG_2
 	addi	r3,r1,STACK_FRAME_OVERHEAD
 #ifdef CONFIG_PPC_CHRP
-	mfspr	r4,SPRN_SPRG2
+	mfspr	r4,SPRN_SPRG_RTAS
 	cmpwi	cr1,r4,0
 	bne	cr1,1f
 #endif
@@ -485,7 +485,7 @@ InstructionTLBMiss:
 	mfspr	r3,SPRN_IMISS
 	lis	r1,PAGE_OFFSET@h		/* check if kernel address */
 	cmplw	0,r1,r3
-	mfspr	r2,SPRN_SPRG3
+	mfspr	r2,SPRN_SPRG_THREAD
 	li	r1,_PAGE_USER|_PAGE_PRESENT /* low addresses tested as user */
 	lwz	r2,PGDIR(r2)
 	bge-	112f
@@ -559,7 +559,7 @@ DataLoadTLBMiss:
 	mfspr	r3,SPRN_DMISS
 	lis	r1,PAGE_OFFSET@h		/* check if kernel address */
 	cmplw	0,r1,r3
-	mfspr	r2,SPRN_SPRG3
+	mfspr	r2,SPRN_SPRG_THREAD
 	li	r1,_PAGE_USER|_PAGE_PRESENT /* low addresses tested as user */
 	lwz	r2,PGDIR(r2)
 	bge-	112f
@@ -598,12 +598,12 @@ END_FTR_SECTION_IFCLR(CPU_FTR_NEED_COHERENT)
 	mtcrf	0x80,r2
 BEGIN_MMU_FTR_SECTION
 	li	r0,1
-	mfspr	r1,SPRN_SPRG4
+	mfspr	r1,SPRN_SPRG_603_LRU
 	rlwinm	r2,r3,20,27,31		/* Get Address bits 15:19 */
 	slw	r0,r0,r2
 	xor	r1,r0,r1
 	srw	r0,r1,r2
-	mtspr   SPRN_SPRG4,r1
+	mtspr   SPRN_SPRG_603_LRU,r1
 	mfspr	r2,SPRN_SRR1
 	rlwimi	r2,r0,31-14,14,14
 	mtspr   SPRN_SRR1,r2
@@ -643,7 +643,7 @@ DataStoreTLBMiss:
 	mfspr	r3,SPRN_DMISS
 	lis	r1,PAGE_OFFSET@h		/* check if kernel address */
 	cmplw	0,r1,r3
-	mfspr	r2,SPRN_SPRG3
+	mfspr	r2,SPRN_SPRG_THREAD
 	li	r1,_PAGE_RW|_PAGE_USER|_PAGE_PRESENT /* access flags */
 	lwz	r2,PGDIR(r2)
 	bge-	112f
@@ -678,12 +678,12 @@ END_FTR_SECTION_IFCLR(CPU_FTR_NEED_COHERENT)
 	mtcrf	0x80,r2
 BEGIN_MMU_FTR_SECTION
 	li	r0,1
-	mfspr	r1,SPRN_SPRG4
+	mfspr	r1,SPRN_SPRG_603_LRU
 	rlwinm	r2,r3,20,27,31		/* Get Address bits 15:19 */
 	slw	r0,r0,r2
 	xor	r1,r0,r1
 	srw	r0,r1,r2
-	mtspr   SPRN_SPRG4,r1
+	mtspr   SPRN_SPRG_603_LRU,r1
 	mfspr	r2,SPRN_SRR1
 	rlwimi	r2,r0,31-14,14,14
 	mtspr   SPRN_SRR1,r2
@@ -864,9 +864,9 @@ __secondary_start:
 	tophys(r4,r2)
 	addi	r4,r4,THREAD	/* phys address of our thread_struct */
 	CLR_TOP32(r4)
-	mtspr	SPRN_SPRG3,r4
+	mtspr	SPRN_SPRG_THREAD,r4
 	li	r3,0
-	mtspr	SPRN_SPRG2,r3	/* 0 => not in RTAS */
+	mtspr	SPRN_SPRG_RTAS,r3	/* 0 => not in RTAS */
 
 	/* enable MMU and jump to start_secondary */
 	li	r4,MSR_KERNEL
@@ -947,9 +947,9 @@ start_here:
 	tophys(r4,r2)
 	addi	r4,r4,THREAD	/* init task's THREAD */
 	CLR_TOP32(r4)
-	mtspr	SPRN_SPRG3,r4
+	mtspr	SPRN_SPRG_THREAD,r4
 	li	r3,0
-	mtspr	SPRN_SPRG2,r3	/* 0 => not in RTAS */
+	mtspr	SPRN_SPRG_RTAS,r3	/* 0 => not in RTAS */
 
 	/* stack */
 	lis	r1,init_thread_union@ha