powerpc/85xx: Save scratch registers to thread info instead of using SPRGs.

We expect this is actually faster, and we end up needing more space than we
can get from the SPRGs in some instances.  This is also useful when running
as a guest OS - SPRGs4-7 do not have guest versions.

8 slots are allocated in thread_info for this even though we only actually
use 4 of them - this allows space for future code to have more scratch
space (and we know we'll need it for things like hugetlb).

Signed-off-by: Ashish Kalra <Ashish.Kalra@freescale.com>
Signed-off-by: Becky Bruce <beckyb@kernel.crashing.org>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>

arch/powerpc/include/asm/processor.h

@@ -20,6 +20,7 @@
 
 #ifndef __ASSEMBLY__
 #include <linux/compiler.h>
+#include <linux/cache.h>
 #include <asm/ptrace.h>
 #include <asm/types.h>
 
@@ -156,6 +157,10 @@ struct thread_struct {
 #endif
 	struct pt_regs	*regs;		/* Pointer to saved register state */
 	mm_segment_t	fs;		/* for get_fs() validation */
+#ifdef CONFIG_BOOKE
+	/* BookE base exception scratch space; align on cacheline */
+	unsigned long	normsave[8] ____cacheline_aligned;
+#endif
 #ifdef CONFIG_PPC32
 	void		*pgdir;		/* root of page-table tree */
 #endif

arch/powerpc/include/asm/reg.h

@@ -872,8 +872,8 @@
 #define SPRN_SPRG_WSCRATCH2	SPRN_SPRG4W
 #define SPRN_SPRG_RSCRATCH3	SPRN_SPRG5R
 #define SPRN_SPRG_WSCRATCH3	SPRN_SPRG5W
-#define SPRN_SPRG_RSCRATCH_MC	SPRN_SPRG6R
-#define SPRN_SPRG_WSCRATCH_MC	SPRN_SPRG6W
+#define SPRN_SPRG_RSCRATCH_MC	SPRN_SPRG1
+#define SPRN_SPRG_WSCRATCH_MC	SPRN_SPRG1
 #define SPRN_SPRG_RSCRATCH4	SPRN_SPRG7R
 #define SPRN_SPRG_WSCRATCH4	SPRN_SPRG7W
 #ifdef CONFIG_E200

arch/powerpc/kernel/asm-offsets.c

@@ -82,6 +82,9 @@ int main(void)
 	DEFINE(KSP, offsetof(struct thread_struct, ksp));
 	DEFINE(KSP_LIMIT, offsetof(struct thread_struct, ksp_limit));
 	DEFINE(PT_REGS, offsetof(struct thread_struct, regs));
+#ifdef CONFIG_BOOKE
+	DEFINE(THREAD_NORMSAVES, offsetof(struct thread_struct, normsave[0]));
+#endif
 	DEFINE(THREAD_FPEXC_MODE, offsetof(struct thread_struct, fpexc_mode));
 	DEFINE(THREAD_FPR0, offsetof(struct thread_struct, fpr[0]));
 	DEFINE(THREAD_FPSCR, offsetof(struct thread_struct, fpscr));

arch/powerpc/kernel/head_booke.h

@@ -20,33 +20,43 @@
 	addi	reg,reg,val@l
 #endif
 
+/*
+ * Macro used to get to thread save registers.
+ * Note that entries 0-3 are used for the prolog code, and the remaining
+ * entries are available for specific exception use in the event a handler
+ * requires more than 4 scratch registers.
+ */
+#define THREAD_NORMSAVE(offset)	(THREAD_NORMSAVES + (offset * 4))
+
 #define NORMAL_EXCEPTION_PROLOG						     \
-	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	   */\
+	mtspr	SPRN_SPRG_WSCRATCH0, r10;	/* save one register */	     \
+	mfspr	r10, SPRN_SPRG_THREAD;					     \
+	stw	r11, THREAD_NORMSAVE(0)(r10);				     \
+	stw	r13, THREAD_NORMSAVE(2)(r10);				     \
+	mfcr	r13;			/* save CR in r13 for now	   */\
 	mfspr	r11,SPRN_SRR1;		/* check whether user or kernel    */\
 	andi.	r11,r11,MSR_PR;						     \
+	mr	r11, r1;						     \
 	beq	1f;							     \
-	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     */\
-	mr	r11,r1;							     \
-	stw	r10,_CCR(r11);          /* save various registers	   */\
+	/* if from user, start at top of this thread's kernel stack */       \
+	lwz	r11, THREAD_INFO-THREAD(r10);				     \
+	ALLOC_STACK_FRAME(r11, THREAD_SIZE);				     \
+1 :	subi	r11, r11, INT_FRAME_SIZE; /* Allocate exception frame */     \
+	stw	r13, _CCR(r11);		/* save various registers */	     \
 	stw	r12,GPR12(r11);						     \
 	stw	r9,GPR9(r11);						     \
-	mfspr	r10,SPRN_SPRG_RSCRATCH0;					\
-	stw	r10,GPR10(r11);						     \
-	mfspr	r12,SPRN_SPRG_RSCRATCH1;				     \
+	mfspr	r13, SPRN_SPRG_RSCRATCH0;				     \
+	stw	r13, GPR10(r11);					     \
+	lwz	r12, THREAD_NORMSAVE(0)(r10);				     \
 	stw	r12,GPR11(r11);						     \
+	lwz	r13, THREAD_NORMSAVE(2)(r10); /* restore r13 */		     \
 	mflr	r10;							     \
 	stw	r10,_LINK(r11);						     \
-	mfspr	r10,SPRN_SPRG_RSCRATCH2;				     \
 	mfspr	r12,SPRN_SRR0;						     \
-	stw	r10,GPR1(r11);						     \
+	stw	r1, GPR1(r11);						     \
 	mfspr	r9,SPRN_SRR1;						     \
-	stw	r10,0(r11);						     \
+	stw	r1, 0(r11);						     \
+	mr	r1, r11;						     \
 	rlwinm	r9,r9,0,14,12;		/* clear MSR_WE (necessary?)	   */\
 	stw	r0,GPR0(r11);						     \
 	lis	r10, STACK_FRAME_REGS_MARKER@ha;/* exception frame marker */ \

arch/powerpc/kernel/head_fsl_booke.S

@@ -346,11 +346,12 @@ interrupt_base:
 	/* Data TLB Error Interrupt */
 	START_EXCEPTION(DataTLBError)
 	mtspr	SPRN_SPRG_WSCRATCH0, r10 /* Save some working registers */
-	mtspr	SPRN_SPRG_WSCRATCH1, r11
-	mtspr	SPRN_SPRG_WSCRATCH2, r12
-	mtspr	SPRN_SPRG_WSCRATCH3, r13
-	mfcr	r11
-	mtspr	SPRN_SPRG_WSCRATCH4, r11
+	mfspr	r10, SPRN_SPRG_THREAD
+	stw	r11, THREAD_NORMSAVE(0)(r10)
+	stw	r12, THREAD_NORMSAVE(1)(r10)
+	stw	r13, THREAD_NORMSAVE(2)(r10)
+	mfcr	r13
+	stw	r13, THREAD_NORMSAVE(3)(r10)
 	mfspr	r10, SPRN_DEAR		/* Get faulting address */
 
 	/* If we are faulting a kernel address, we have to use the
@@ -416,11 +417,12 @@ interrupt_base:
 	/* The bailout.  Restore registers to pre-exception conditions
 	 * and call the heavyweights to help us out.
 	 */
-	mfspr	r11, SPRN_SPRG_RSCRATCH4
+	mfspr	r10, SPRN_SPRG_THREAD
+	lwz	r11, THREAD_NORMSAVE(3)(r10)
 	mtcr	r11
-	mfspr	r13, SPRN_SPRG_RSCRATCH3
-	mfspr	r12, SPRN_SPRG_RSCRATCH2
-	mfspr	r11, SPRN_SPRG_RSCRATCH1
+	lwz	r13, THREAD_NORMSAVE(2)(r10)
+	lwz	r12, THREAD_NORMSAVE(1)(r10)
+	lwz	r11, THREAD_NORMSAVE(0)(r10)
 	mfspr	r10, SPRN_SPRG_RSCRATCH0
 	b	DataStorage
 
@@ -432,11 +434,12 @@ interrupt_base:
 	 */
 	START_EXCEPTION(InstructionTLBError)
 	mtspr	SPRN_SPRG_WSCRATCH0, r10 /* Save some working registers */
-	mtspr	SPRN_SPRG_WSCRATCH1, r11
-	mtspr	SPRN_SPRG_WSCRATCH2, r12
-	mtspr	SPRN_SPRG_WSCRATCH3, r13
-	mfcr	r11
-	mtspr	SPRN_SPRG_WSCRATCH4, r11
+	mfspr	r10, SPRN_SPRG_THREAD
+	stw	r11, THREAD_NORMSAVE(0)(r10)
+	stw	r12, THREAD_NORMSAVE(1)(r10)
+	stw	r13, THREAD_NORMSAVE(2)(r10)
+	mfcr	r13
+	stw	r13, THREAD_NORMSAVE(3)(r10)
 	mfspr	r10, SPRN_SRR0		/* Get faulting address */
 
 	/* If we are faulting a kernel address, we have to use the
@@ -496,11 +499,12 @@ interrupt_base:
 	/* The bailout.  Restore registers to pre-exception conditions
 	 * and call the heavyweights to help us out.
 	 */
-	mfspr	r11, SPRN_SPRG_RSCRATCH4
+	mfspr	r10, SPRN_SPRG_THREAD
+	lwz	r11, THREAD_NORMSAVE(3)(r10)
 	mtcr	r11
-	mfspr	r13, SPRN_SPRG_RSCRATCH3
-	mfspr	r12, SPRN_SPRG_RSCRATCH2
-	mfspr	r11, SPRN_SPRG_RSCRATCH1
+	lwz	r13, THREAD_NORMSAVE(2)(r10)
+	lwz	r12, THREAD_NORMSAVE(1)(r10)
+	lwz	r11, THREAD_NORMSAVE(0)(r10)
 	mfspr	r10, SPRN_SPRG_RSCRATCH0
 	b	InstructionStorage
 
@@ -621,11 +625,12 @@ END_MMU_FTR_SECTION_IFSET(MMU_FTR_BIG_PHYS)
 	tlbwe
 
 	/* Done...restore registers and get out of here.  */
-	mfspr	r11, SPRN_SPRG_RSCRATCH4
+	mfspr	r10, SPRN_SPRG_THREAD
+	lwz	r11, THREAD_NORMSAVE(3)(r10)
 	mtcr	r11
-	mfspr	r13, SPRN_SPRG_RSCRATCH3
-	mfspr	r12, SPRN_SPRG_RSCRATCH2
-	mfspr	r11, SPRN_SPRG_RSCRATCH1
+	lwz	r13, THREAD_NORMSAVE(2)(r10)
+	lwz	r12, THREAD_NORMSAVE(1)(r10)
+	lwz	r11, THREAD_NORMSAVE(0)(r10)
 	mfspr	r10, SPRN_SPRG_RSCRATCH0
 	rfi					/* Force context change */