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, 30 deletions

diff --git a/arch/powerpc/kernel/head_booke.h b/arch/powerpc/kernel/head_booke.h
index 5f9febc..50504ae 100644
--- a/arch/powerpc/kernel/head_booke.h
+++ b/arch/powerpc/kernel/head_booke.h
@@ -20,14 +20,14 @@
 #endif
 
 #define NORMAL_EXCEPTION_PROLOG						     \
-	mtspr	SPRN_SPRG0,r10;		/* save two registers to work with */\
-	mtspr	SPRN_SPRG1,r11;						     \
-	mtspr	SPRN_SPRG4W,r1;						     \
+	mtspr	SPRN_SPRG_WSCRATCH0,r10;/* save two registers to work with */\
+	mtspr	SPRN_SPRG_WSCRATCH1,r11;				     \
+	mtspr	SPRN_SPRG_WSCRATCH2,r1;					     \
 	mfcr	r10;			/* save CR in r10 for now	   */\
 	mfspr	r11,SPRN_SRR1;		/* check whether user or kernel    */\
 	andi.	r11,r11,MSR_PR;						     \
 	beq	1f;							     \
-	mfspr	r1,SPRN_SPRG3;		/* if from user, start at top of   */\
+	mfspr	r1,SPRN_SPRG_THREAD;	/* if from user, start at top of   */\
 	lwz	r1,THREAD_INFO-THREAD(r1); /* this thread's kernel stack   */\
 	ALLOC_STACK_FRAME(r1, THREAD_SIZE);				     \
 1:	subi	r1,r1,INT_FRAME_SIZE;	/* Allocate an exception frame     */\
@@ -35,13 +35,13 @@
 	stw	r10,_CCR(r11);          /* save various registers	   */\
 	stw	r12,GPR12(r11);						     \
 	stw	r9,GPR9(r11);						     \
-	mfspr	r10,SPRN_SPRG0;						     \
+	mfspr	r10,SPRN_SPRG_RSCRATCH0;					\
 	stw	r10,GPR10(r11);						     \
-	mfspr	r12,SPRN_SPRG1;						     \
+	mfspr	r12,SPRN_SPRG_RSCRATCH1;				     \
 	stw	r12,GPR11(r11);						     \
 	mflr	r10;							     \
 	stw	r10,_LINK(r11);						     \
-	mfspr	r10,SPRN_SPRG4R;					     \
+	mfspr	r10,SPRN_SPRG_RSCRATCH2;				     \
 	mfspr	r12,SPRN_SRR0;						     \
 	stw	r10,GPR1(r11);						     \
 	mfspr	r9,SPRN_SRR1;						     \
@@ -69,21 +69,11 @@
  * providing configurations that micro-optimize space usage.
  */
 
-/* CRIT_SPRG only used in critical exception handling */
-#define CRIT_SPRG	SPRN_SPRG2
-/* MCHECK_SPRG only used in machine check exception handling */
-#define MCHECK_SPRG	SPRN_SPRG6W
-
-#define MCHECK_STACK_BASE	mcheckirq_ctx
+#define MC_STACK_BASE		mcheckirq_ctx
 #define CRIT_STACK_BASE		critirq_ctx
 
 /* only on e500mc/e200 */
-#define DEBUG_STACK_BASE	dbgirq_ctx
-#ifdef CONFIG_E200
-#define DEBUG_SPRG		SPRN_SPRG6W
-#else
-#define DEBUG_SPRG		SPRN_SPRG9
-#endif
+#define DBG_STACK_BASE		dbgirq_ctx
 
 #define EXC_LVL_FRAME_OVERHEAD	(THREAD_SIZE - INT_FRAME_SIZE - EXC_LVL_SIZE)
 
@@ -110,7 +100,7 @@
  * critical/machine check exception stack at low physical addresses.
  */
 #define EXC_LEVEL_EXCEPTION_PROLOG(exc_level, exc_level_srr0, exc_level_srr1) \
-	mtspr	exc_level##_SPRG,r8;					     \
+	mtspr	SPRN_SPRG_WSCRATCH_##exc_level,r8;			     \
 	BOOKE_LOAD_EXC_LEVEL_STACK(exc_level);/* r8 points to the exc_level stack*/ \
 	stw	r9,GPR9(r8);		/* save various registers	   */\
 	mfcr	r9;			/* save CR in r9 for now	   */\
@@ -119,7 +109,7 @@
 	stw	r9,_CCR(r8);		/* save CR on stack		   */\
 	mfspr	r10,exc_level_srr1;	/* check whether user or kernel    */\
 	andi.	r10,r10,MSR_PR;						     \
-	mfspr	r11,SPRN_SPRG3;		/* if from user, start at top of   */\
+	mfspr	r11,SPRN_SPRG_THREAD;	/* if from user, start at top of   */\
 	lwz	r11,THREAD_INFO-THREAD(r11); /* this thread's kernel stack */\
 	addi	r11,r11,EXC_LVL_FRAME_OVERHEAD;	/* allocate stack frame    */\
 	beq	1f;							     \
@@ -140,7 +130,7 @@
 	lwz	r9,TI_TASK-EXC_LVL_FRAME_OVERHEAD(r11);			     \
 	stw	r9,TI_TASK-EXC_LVL_FRAME_OVERHEAD(r8);			     \
 	mr	r11,r8;							     \
-2:	mfspr	r8,exc_level##_SPRG;					     \
+2:	mfspr	r8,SPRN_SPRG_RSCRATCH_##exc_level;			     \
 	stw	r12,GPR12(r11);		/* save various registers	   */\
 	mflr	r10;							     \
 	stw	r10,_LINK(r11);						     \
@@ -161,9 +151,9 @@
 #define CRITICAL_EXCEPTION_PROLOG \
 		EXC_LEVEL_EXCEPTION_PROLOG(CRIT, SPRN_CSRR0, SPRN_CSRR1)
 #define DEBUG_EXCEPTION_PROLOG \
-		EXC_LEVEL_EXCEPTION_PROLOG(DEBUG, SPRN_DSRR0, SPRN_DSRR1)
+		EXC_LEVEL_EXCEPTION_PROLOG(DBG, SPRN_DSRR0, SPRN_DSRR1)
 #define MCHECK_EXCEPTION_PROLOG \
-		EXC_LEVEL_EXCEPTION_PROLOG(MCHECK, SPRN_MCSRR0, SPRN_MCSRR1)
+		EXC_LEVEL_EXCEPTION_PROLOG(MC, SPRN_MCSRR0, SPRN_MCSRR1)
 
 /*
  * Exception vectors.
@@ -282,13 +272,13 @@ label:
 	mtspr	SPRN_DSRR1,r9;						      \
 	lwz	r9,GPR9(r11);						      \
 	lwz	r12,GPR12(r11);						      \
-	mtspr	DEBUG_SPRG,r8;						      \
-	BOOKE_LOAD_EXC_LEVEL_STACK(DEBUG); /* r8 points to the debug stack */ \
+	mtspr	SPRN_SPRG_WSCRATCH_DBG,r8;				      \
+	BOOKE_LOAD_EXC_LEVEL_STACK(DBG); /* r8 points to the debug stack */ \
 	lwz	r10,GPR10(r8);						      \
 	lwz	r11,GPR11(r8);						      \
-	mfspr	r8,DEBUG_SPRG;						      \
+	mfspr	r8,SPRN_SPRG_RSCRATCH_DBG;				      \
 									      \
-	PPC_RFDI;								      \
+	PPC_RFDI;							      \
 	b	.;							      \
 									      \
 	/* continue normal handling for a debug exception... */		      \
@@ -335,11 +325,11 @@ label:
 	mtspr	SPRN_CSRR1,r9;						      \
 	lwz	r9,GPR9(r11);						      \
 	lwz	r12,GPR12(r11);						      \
-	mtspr	CRIT_SPRG,r8;						      \
+	mtspr	SPRN_SPRG_WSCRATCH_CRIT,r8;				      \
 	BOOKE_LOAD_EXC_LEVEL_STACK(CRIT); /* r8 points to the debug stack */  \
 	lwz	r10,GPR10(r8);						      \
 	lwz	r11,GPR11(r8);						      \
-	mfspr	r8,CRIT_SPRG;						      \
+	mfspr	r8,SPRN_SPRG_RSCRATCH_CRIT;				      \
 									      \
 	rfci;								      \
 	b	.;							      \