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, 9 insertions, 9 deletions

diff --git a/arch/powerpc/include/asm/exception-64s.h b/arch/powerpc/include/asm/exception-64s.h
index d3d4534e3c74..773e380b5fe8 100644
--- a/arch/powerpc/include/asm/exception-64s.h
+++ b/arch/powerpc/include/asm/exception-64s.h
@@ -57,12 +57,12 @@
         addi    reg,reg,(label)-_stext; /* virt addr of handler ... */
 
 #define EXCEPTION_PROLOG_1(area)                                \
-        mfspr   r13,SPRN_SPRG3;         /* get paca address into r13 */ \
+        mfspr   r13,SPRN_SPRG_PACA;     /* get paca address into r13 */ \
         std     r9,area+EX_R9(r13);     /* save r9 - r12 */             \
         std     r10,area+EX_R10(r13);                                   \
         std     r11,area+EX_R11(r13);                                   \
         std     r12,area+EX_R12(r13);                                   \
-        mfspr   r9,SPRN_SPRG1;                                          \
+        mfspr   r9,SPRN_SPRG_SCRATCH0;                                  \
         std     r9,area+EX_R13(r13);                                    \
         mfcr    r9
 
@@ -144,7 +144,7 @@
         .globl label##_pSeries;                         \
 label##_pSeries:                                        \
         HMT_MEDIUM;                                     \
-        mtspr   SPRN_SPRG1,r13;         /* save r13 */  \
+        mtspr   SPRN_SPRG_SCRATCH0,r13;         /* save r13 */  \
         EXCEPTION_PROLOG_PSERIES(PACA_EXGEN, label##_common)
 
 #define HSTD_EXCEPTION_PSERIES(n, label)                \
@@ -152,13 +152,13 @@ label##_pSeries:					\
         .globl label##_pSeries;                         \
 label##_pSeries:                                        \
         HMT_MEDIUM;                                     \
-        mtspr   SPRN_SPRG1,r20;         /* save r20 */  \
+        mtspr   SPRN_SPRG_SCRATCH0,r20; /* save r20 */  \
         mfspr   r20,SPRN_HSRR0;         /* copy HSRR0 to SRR0 */ \
         mtspr   SPRN_SRR0,r20;                          \
         mfspr   r20,SPRN_HSRR1;         /* copy HSRR0 to SRR0 */ \
         mtspr   SPRN_SRR1,r20;                          \
-        mfspr   r20,SPRN_SPRG1;         /* restore r20 */ \
-        mtspr   SPRN_SPRG1,r13;         /* save r13 */  \
+        mfspr   r20,SPRN_SPRG_SCRATCH0; /* restore r20 */ \
+        mtspr   SPRN_SPRG_SCRATCH0,r13;         /* save r13 */  \
         EXCEPTION_PROLOG_PSERIES(PACA_EXGEN, label##_common)
 
 
@@ -167,15 +167,15 @@ label##_pSeries:					\
         .globl label##_pSeries;                                         \
 label##_pSeries:                                                        \
         HMT_MEDIUM;                                                     \
-        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     r9,PACA_EXGEN+EX_R9(r13);       /* save r9, r10 */      \
         std     r10,PACA_EXGEN+EX_R10(r13);                             \
         lbz     r10,PACASOFTIRQEN(r13);                                 \
         mfcr    r9;                                                     \
         cmpwi   r10,0;                                                  \
         beq     masked_interrupt;                                       \
-        mfspr   r10,SPRN_SPRG1;                                         \
+        mfspr   r10,SPRN_SPRG_SCRATCH0;                                 \
         std     r10,PACA_EXGEN+EX_R13(r13);                             \
         std     r11,PACA_EXGEN+EX_R11(r13);                             \
         std     r12,PACA_EXGEN+EX_R12(r13);                             \