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>
diff --git a/arch/powerpc/kernel/head_8xx.S b/arch/powerpc/kernel/head_8xx.S
index 52ff8c5..6ded19d 100644
--- a/arch/powerpc/kernel/head_8xx.S
+++ b/arch/powerpc/kernel/head_8xx.S
@@ -110,8 +110,8 @@
* 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
@@ -121,7 +121,7 @@
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); \
@@ -133,9 +133,9 @@
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); \
@@ -603,8 +603,9 @@
/* ptr to phys current thread */
tophys(r4,r2)
addi r4,r4,THREAD /* init task's THREAD */
- mtspr SPRN_SPRG3,r4
+ mtspr SPRN_SPRG_THREAD,r4
li r3,0
+ /* XXX What is that for ? SPRG2 appears otherwise unused on 8xx */
mtspr SPRN_SPRG2,r3 /* 0 => r1 has kernel sp */
/* stack */
