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, 10 insertions, 10 deletions

diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S
index 3cadba60a4b6..1175a8539e6c 100644
--- a/arch/powerpc/kernel/entry_32.S
+++ b/arch/powerpc/kernel/entry_32.S
@@ -88,7 +88,7 @@ crit_transfer_to_handler:
         mfspr   r0,SPRN_SRR1
         stw     r0,_SRR1(r11)
 
-        mfspr   r8,SPRN_SPRG3
+        mfspr   r8,SPRN_SPRG_THREAD
         lwz     r0,KSP_LIMIT(r8)
         stw     r0,SAVED_KSP_LIMIT(r11)
         rlwimi  r0,r1,0,0,(31-THREAD_SHIFT)
@@ -108,7 +108,7 @@ crit_transfer_to_handler:
         mfspr   r0,SPRN_SRR1
         stw     r0,crit_srr1@l(0)
 
-        mfspr   r8,SPRN_SPRG3
+        mfspr   r8,SPRN_SPRG_THREAD
         lwz     r0,KSP_LIMIT(r8)
         stw     r0,saved_ksp_limit@l(0)
         rlwimi  r0,r1,0,0,(31-THREAD_SHIFT)
@@ -138,7 +138,7 @@ transfer_to_handler:
         mfspr   r2,SPRN_XER
         stw     r12,_CTR(r11)
         stw     r2,_XER(r11)
-        mfspr   r12,SPRN_SPRG3
+        mfspr   r12,SPRN_SPRG_THREAD
         addi    r2,r12,-THREAD
         tovirt(r2,r2)                   /* set r2 to current */
         beq     2f                      /* if from user, fix up THREAD.regs */
@@ -680,7 +680,7 @@ END_FTR_SECTION_IFSET(CPU_FTR_SPE)
 
         tophys(r0,r4)
         CLR_TOP32(r0)
-        mtspr   SPRN_SPRG3,r0   /* Update current THREAD phys addr */
+        mtspr   SPRN_SPRG_THREAD,r0     /* Update current THREAD phys addr */
         lwz     r1,KSP(r4)      /* Load new stack pointer */
 
         /* save the old current 'last' for return value */
@@ -1057,7 +1057,7 @@ exc_exit_restart_end:
 #ifdef CONFIG_40x
         .globl  ret_from_crit_exc
 ret_from_crit_exc:
-        mfspr   r9,SPRN_SPRG3
+        mfspr   r9,SPRN_SPRG_THREAD
         lis     r10,saved_ksp_limit@ha;
         lwz     r10,saved_ksp_limit@l(r10);
         tovirt(r9,r9);
@@ -1074,7 +1074,7 @@ ret_from_crit_exc:
 #ifdef CONFIG_BOOKE
         .globl  ret_from_crit_exc
 ret_from_crit_exc:
-        mfspr   r9,SPRN_SPRG3
+        mfspr   r9,SPRN_SPRG_THREAD
         lwz     r10,SAVED_KSP_LIMIT(r1)
         stw     r10,KSP_LIMIT(r9)
         RESTORE_xSRR(SRR0,SRR1);
@@ -1083,7 +1083,7 @@ ret_from_crit_exc:
 
         .globl  ret_from_debug_exc
 ret_from_debug_exc:
-        mfspr   r9,SPRN_SPRG3
+        mfspr   r9,SPRN_SPRG_THREAD
         lwz     r10,SAVED_KSP_LIMIT(r1)
         stw     r10,KSP_LIMIT(r9)
         lwz     r9,THREAD_INFO-THREAD(r9)
@@ -1097,7 +1097,7 @@ ret_from_debug_exc:
 
         .globl  ret_from_mcheck_exc
 ret_from_mcheck_exc:
-        mfspr   r9,SPRN_SPRG3
+        mfspr   r9,SPRN_SPRG_THREAD
         lwz     r10,SAVED_KSP_LIMIT(r1)
         stw     r10,KSP_LIMIT(r9)
         RESTORE_xSRR(SRR0,SRR1);
@@ -1255,7 +1255,7 @@ _GLOBAL(enter_rtas)
         MTMSRD(r0)              /* don't get trashed */
         li      r9,MSR_KERNEL & ~(MSR_IR|MSR_DR)
         mtlr    r6
-        mtspr   SPRN_SPRG2,r7
+        mtspr   SPRN_SPRG_RTAS,r7
         mtspr   SPRN_SRR0,r8
         mtspr   SPRN_SRR1,r9
         RFI
@@ -1265,7 +1265,7 @@ _GLOBAL(enter_rtas)
         FIX_SRR1(r9,r0)
         addi    r1,r1,INT_FRAME_SIZE
         li      r0,0
-        mtspr   SPRN_SPRG2,r0
+        mtspr   SPRN_SPRG_RTAS,r0
         mtspr   SPRN_SRR0,r8
         mtspr   SPRN_SRR1,r9
         RFI                     /* return to caller */