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>

2 files changed, 16 insertions, 16 deletions

diff --git a/arch/powerpc/platforms/iseries/exception.S b/arch/powerpc/platforms/iseries/exception.S
index 2f58152..2b80759 100644
--- a/arch/powerpc/platforms/iseries/exception.S
+++ b/arch/powerpc/platforms/iseries/exception.S
@@ -47,7 +47,7 @@ system_reset_iSeries:
 	LOAD_REG_ADDR(r13, paca)
 	mulli	r0,r23,PACA_SIZE
 	add	r13,r13,r0
-	mtspr	SPRN_SPRG3,r13		/* Save it away for the future */
+	mtspr	SPRN_SPRG_PACA,r13	/* Save it away for the future */
 	mfmsr	r24
 	ori	r24,r24,MSR_RI
 	mtmsrd	r24			/* RI on */
@@ -116,7 +116,7 @@ iSeries_secondary_smp_loop:
 #endif /* CONFIG_SMP */
 	li	r0,-1			/* r0=-1 indicates a Hypervisor call */
 	sc				/* Invoke the hypervisor via a system call */
-	mfspr	r13,SPRN_SPRG3		/* Put r13 back ???? */
+	mfspr	r13,SPRN_SPRG_PACA	/* Put r13 back ???? */
 	b	2b			/* If SMP not configured, secondaries
 					 * loop forever */
 
@@ -126,9 +126,9 @@ iSeries_secondary_smp_loop:
 
 	.globl data_access_iSeries
 data_access_iSeries:
-	mtspr	SPRN_SPRG1,r13
+	mtspr	SPRN_SPRG_SCRATCH0,r13
 BEGIN_FTR_SECTION
-	mtspr	SPRN_SPRG2,r12
+	mtspr	SPRN_SPRG_SCRATCH1,r12
 	mfspr	r13,SPRN_DAR
 	mfspr	r12,SPRN_DSISR
 	srdi	r13,r13,60
@@ -137,7 +137,7 @@ BEGIN_FTR_SECTION
 	cmpwi	r13,0x2c
 	beq	.do_stab_bolted_iSeries
 	mtcrf	0x80,r12
-	mfspr	r12,SPRN_SPRG2
+	mfspr	r12,SPRN_SPRG_SCRATCH1
 END_FTR_SECTION_IFCLR(CPU_FTR_SLB)
 	EXCEPTION_PROLOG_1(PACA_EXGEN)
 	EXCEPTION_PROLOG_ISERIES_1
@@ -145,15 +145,15 @@ END_FTR_SECTION_IFCLR(CPU_FTR_SLB)
 
 .do_stab_bolted_iSeries:
 	mtcrf	0x80,r12
-	mfspr	r12,SPRN_SPRG2
+	mfspr	r12,SPRN_SPRG_SCRATCH1
 	EXCEPTION_PROLOG_1(PACA_EXSLB)
 	EXCEPTION_PROLOG_ISERIES_1
 	b	.do_stab_bolted
 
 	.globl	data_access_slb_iSeries
 data_access_slb_iSeries:
-	mtspr	SPRN_SPRG1,r13		/* save r13 */
-	mfspr	r13,SPRN_SPRG3		/* get paca address into r13 */
+	mtspr	SPRN_SPRG_SCRATCH0,r13	/* save r13 */
+	mfspr	r13,SPRN_SPRG_PACA	/* get paca address into r13 */
 	std	r3,PACA_EXSLB+EX_R3(r13)
 	mfspr	r3,SPRN_DAR
 	std	r9,PACA_EXSLB+EX_R9(r13)
@@ -165,7 +165,7 @@ data_access_slb_iSeries:
 	std	r10,PACA_EXSLB+EX_R10(r13)
 	std	r11,PACA_EXSLB+EX_R11(r13)
 	std	r12,PACA_EXSLB+EX_R12(r13)
-	mfspr	r10,SPRN_SPRG1
+	mfspr	r10,SPRN_SPRG_SCRATCH0
 	std	r10,PACA_EXSLB+EX_R13(r13)
 	ld	r12,PACALPPACAPTR(r13)
 	ld	r12,LPPACASRR1(r12)
@@ -175,8 +175,8 @@ data_access_slb_iSeries:
 
 	.globl	instruction_access_slb_iSeries
 instruction_access_slb_iSeries:
-	mtspr	SPRN_SPRG1,r13		/* save r13 */
-	mfspr	r13,SPRN_SPRG3		/* get paca address into r13 */
+	mtspr	SPRN_SPRG_SCRATCH0,r13	/* save r13 */
+	mfspr	r13,SPRN_SPRG_PACA	/* get paca address into r13 */
 	std	r3,PACA_EXSLB+EX_R3(r13)
 	ld	r3,PACALPPACAPTR(r13)
 	ld	r3,LPPACASRR0(r3)	/* get SRR0 value */
@@ -189,7 +189,7 @@ instruction_access_slb_iSeries:
 	std	r10,PACA_EXSLB+EX_R10(r13)
 	std	r11,PACA_EXSLB+EX_R11(r13)
 	std	r12,PACA_EXSLB+EX_R12(r13)
-	mfspr	r10,SPRN_SPRG1
+	mfspr	r10,SPRN_SPRG_SCRATCH0
 	std	r10,PACA_EXSLB+EX_R13(r13)
 	ld	r12,PACALPPACAPTR(r13)
 	ld	r12,LPPACASRR1(r12)
@@ -200,7 +200,7 @@ slb_miss_user_iseries:
 	std	r10,PACA_EXGEN+EX_R10(r13)
 	std	r11,PACA_EXGEN+EX_R11(r13)
 	std	r12,PACA_EXGEN+EX_R12(r13)
-	mfspr	r10,SPRG1
+	mfspr	r10,SPRG_SCRATCH0
 	ld	r11,PACA_EXSLB+EX_R9(r13)
 	ld	r12,PACA_EXSLB+EX_R3(r13)
 	std	r10,PACA_EXGEN+EX_R13(r13)
@@ -221,7 +221,7 @@ slb_miss_user_iseries:
 	.globl	system_call_iSeries
 system_call_iSeries:
 	mr	r9,r13
-	mfspr	r13,SPRN_SPRG3
+	mfspr	r13,SPRN_SPRG_PACA
 	EXCEPTION_PROLOG_ISERIES_1
 	b	system_call_common
 
diff --git a/arch/powerpc/platforms/iseries/exception.h b/arch/powerpc/platforms/iseries/exception.h
index e26eb86..bae3fba 100644
--- a/arch/powerpc/platforms/iseries/exception.h
+++ b/arch/powerpc/platforms/iseries/exception.h
@@ -38,7 +38,7 @@
 	.globl label##_iSeries;						\
 label##_iSeries:							\
 	HMT_MEDIUM;							\
-	mtspr	SPRN_SPRG1,r13;		/* save r13 */			\
+	mtspr	SPRN_SPRG_SCRATCH0,r13;	/* save r13 */			\
 	EXCEPTION_PROLOG_1(area);					\
 	EXCEPTION_PROLOG_ISERIES_1;					\
 	b	label##_common
@@ -47,7 +47,7 @@ label##_iSeries:							\
 	.globl label##_iSeries;						\
 label##_iSeries:							\
 	HMT_MEDIUM;							\
-	mtspr	SPRN_SPRG1,r13;		/* save r13 */			\
+	mtspr	SPRN_SPRG_SCRATCH0,r13;	/* save r13 */			\
 	EXCEPTION_PROLOG_1(PACA_EXGEN);					\
 	lbz	r10,PACASOFTIRQEN(r13);					\
 	cmpwi	0,r10,0;						\