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, 62 insertions, 62 deletions

diff --git a/arch/powerpc/kernel/head_40x.S b/arch/powerpc/kernel/head_40x.S
index 0c96911d4299..a90625f9b485 100644
--- a/arch/powerpc/kernel/head_40x.S
+++ b/arch/powerpc/kernel/head_40x.S
@@ -103,21 +103,21 @@ _ENTRY(saved_ksp_limit)
 
 /*
  * Exception vector entry code. This code runs with address translation
- * turned off (i.e. using physical addresses). We assume SPRG3 has the
- * physical address of the current task thread_struct.
+ * turned off (i.e. using physical addresses). We assume SPRG_THREAD has
+ * the physical address of the current task thread_struct.
  * Note that we have to have decremented r1 before we write to any fields
  * of the exception frame, since a critical interrupt could occur at any
  * time, and it will write to the area immediately below the current r1.
  */
 #define NORMAL_EXCEPTION_PROLOG                                              \
-        mtspr   SPRN_SPRG0,r10;         /* save two registers to work with */\
-        mtspr   SPRN_SPRG1,r11;                                              \
-        mtspr   SPRN_SPRG2,r1;                                               \
+        mtspr   SPRN_SPRG_SCRATCH0,r10; /* save two registers to work with */\
+        mtspr   SPRN_SPRG_SCRATCH1,r11;                                      \
+        mtspr   SPRN_SPRG_SCRATCH2,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   */\
         addi    r1,r1,THREAD_SIZE;                                           \
 1:      subi    r1,r1,INT_FRAME_SIZE;   /* Allocate an exception frame     */\
@@ -125,13 +125,13 @@ _ENTRY(saved_ksp_limit)
         stw     r10,_CCR(r11);          /* save various 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);                                              \
-        mfspr   r10,SPRN_SPRG2;                                              \
+        mfspr   r10,SPRN_SPRG_SCRATCH2;                                      \
         mfspr   r12,SPRN_SRR0;                                               \
         stw     r10,GPR1(r11);                                               \
         mfspr   r9,SPRN_SRR1;                                                \
@@ -160,7 +160,7 @@ _ENTRY(saved_ksp_limit)
         lwz     r11,critirq_ctx@l(r11);                                      \
         beq     1f;                                                          \
         /* COMING FROM USER MODE */                                          \
-        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 */\
 1:      addi    r11,r11,THREAD_SIZE-INT_FRAME_SIZE; /* Alloc an excpt frm  */\
         tophys(r11,r11);                                                     \
@@ -265,8 +265,8 @@ label:
  * and exit.  Otherwise, we call heavywight functions to do the work.
  */
         START_EXCEPTION(0x0300, DataStorage)
-        mtspr   SPRN_SPRG0, r10         /* Save some working registers */
-        mtspr   SPRN_SPRG1, r11
+        mtspr   SPRN_SPRG_SCRATCH0, r10 /* Save some working registers */
+        mtspr   SPRN_SPRG_SCRATCH1, r11
 #ifdef CONFIG_403GCX
         stw     r12, 0(r0)
         stw     r9, 4(r0)
@@ -275,12 +275,12 @@ label:
         stw     r11, 8(r0)
         stw     r12, 12(r0)
 #else
-        mtspr   SPRN_SPRG4, r12
-        mtspr   SPRN_SPRG5, r9
+        mtspr   SPRN_SPRG_SCRATCH3, r12
+        mtspr   SPRN_SPRG_SCRATCH4, r9
         mfcr    r11
         mfspr   r12, SPRN_PID
-        mtspr   SPRN_SPRG7, r11
-        mtspr   SPRN_SPRG6, r12
+        mtspr   SPRN_SPRG_SCRATCH6, r11
+        mtspr   SPRN_SPRG_SCRATCH5, r12
 #endif
 
         /* First, check if it was a zone fault (which means a user
@@ -308,7 +308,7 @@ label:
         /* Get the PGD for the current thread.
          */
 3:
-        mfspr   r11,SPRN_SPRG3
+        mfspr   r11,SPRN_SPRG_THREAD
         lwz     r11,PGDIR(r11)
 4:
         tophys(r11, r11)
@@ -355,15 +355,15 @@ label:
         lwz     r9, 4(r0)
         lwz     r12, 0(r0)
 #else
-        mfspr   r12, SPRN_SPRG6
-        mfspr   r11, SPRN_SPRG7
+        mfspr   r12, SPRN_SPRG_SCRATCH5
+        mfspr   r11, SPRN_SPRG_SCRATCH6
         mtspr   SPRN_PID, r12
         mtcr    r11
-        mfspr   r9, SPRN_SPRG5
-        mfspr   r12, SPRN_SPRG4
+        mfspr   r9, SPRN_SPRG_SCRATCH4
+        mfspr   r12, SPRN_SPRG_SCRATCH3
 #endif
-        mfspr   r11, SPRN_SPRG1
-        mfspr   r10, SPRN_SPRG0
+        mfspr   r11, SPRN_SPRG_SCRATCH1
+        mfspr   r10, SPRN_SPRG_SCRATCH0
         PPC405_ERR77_SYNC
         rfi                     /* Should sync shadow TLBs */
         b       .               /* prevent prefetch past rfi */
@@ -380,15 +380,15 @@ label:
         lwz     r9, 4(r0)
         lwz     r12, 0(r0)
 #else
-        mfspr   r12, SPRN_SPRG6
-        mfspr   r11, SPRN_SPRG7
+        mfspr   r12, SPRN_SPRG_SCRATCH5
+        mfspr   r11, SPRN_SPRG_SCRATCH6
         mtspr   SPRN_PID, r12
         mtcr    r11
-        mfspr   r9, SPRN_SPRG5
-        mfspr   r12, SPRN_SPRG4
+        mfspr   r9, SPRN_SPRG_SCRATCH4
+        mfspr   r12, SPRN_SPRG_SCRATCH3
 #endif
-        mfspr   r11, SPRN_SPRG1
-        mfspr   r10, SPRN_SPRG0
+        mfspr   r11, SPRN_SPRG_SCRATCH1
+        mfspr   r10, SPRN_SPRG_SCRATCH0
         b       DataAccess
 
 /*
@@ -466,8 +466,8 @@ label:
  * load TLB entries from the page table if they exist.
  */
         START_EXCEPTION(0x1100, DTLBMiss)
-        mtspr   SPRN_SPRG0, r10         /* Save some working registers */
-        mtspr   SPRN_SPRG1, r11
+        mtspr   SPRN_SPRG_SCRATCH0, r10 /* Save some working registers */
+        mtspr   SPRN_SPRG_SCRATCH1, r11
 #ifdef CONFIG_403GCX
         stw     r12, 0(r0)
         stw     r9, 4(r0)
@@ -476,12 +476,12 @@ label:
         stw     r11, 8(r0)
         stw     r12, 12(r0)
 #else
-        mtspr   SPRN_SPRG4, r12
-        mtspr   SPRN_SPRG5, r9
+        mtspr   SPRN_SPRG_SCRATCH3, r12
+        mtspr   SPRN_SPRG_SCRATCH4, r9
         mfcr    r11
         mfspr   r12, SPRN_PID
-        mtspr   SPRN_SPRG7, r11
-        mtspr   SPRN_SPRG6, r12
+        mtspr   SPRN_SPRG_SCRATCH6, r11
+        mtspr   SPRN_SPRG_SCRATCH5, r12
 #endif
         mfspr   r10, SPRN_DEAR          /* Get faulting address */
 
@@ -500,7 +500,7 @@ label:
         /* Get the PGD for the current thread.
          */
 3:
-        mfspr   r11,SPRN_SPRG3
+        mfspr   r11,SPRN_SPRG_THREAD
         lwz     r11,PGDIR(r11)
 4:
         tophys(r11, r11)
@@ -550,15 +550,15 @@ label:
         lwz     r9, 4(r0)
         lwz     r12, 0(r0)
 #else
-        mfspr   r12, SPRN_SPRG6
-        mfspr   r11, SPRN_SPRG7
+        mfspr   r12, SPRN_SPRG_SCRATCH5
+        mfspr   r11, SPRN_SPRG_SCRATCH6
         mtspr   SPRN_PID, r12
         mtcr    r11
-        mfspr   r9, SPRN_SPRG5
-        mfspr   r12, SPRN_SPRG4
+        mfspr   r9, SPRN_SPRG_SCRATCH4
+        mfspr   r12, SPRN_SPRG_SCRATCH3
 #endif
-        mfspr   r11, SPRN_SPRG1
-        mfspr   r10, SPRN_SPRG0
+        mfspr   r11, SPRN_SPRG_SCRATCH1
+        mfspr   r10, SPRN_SPRG_SCRATCH0
         b       DataAccess
 
 /* 0x1200 - Instruction TLB Miss Exception
@@ -566,8 +566,8 @@ label:
  * registers and bailout to a different point.
  */
         START_EXCEPTION(0x1200, ITLBMiss)
-        mtspr   SPRN_SPRG0, r10         /* Save some working registers */
-        mtspr   SPRN_SPRG1, r11
+        mtspr   SPRN_SPRG_SCRATCH0, r10  /* Save some working registers */
+        mtspr   SPRN_SPRG_SCRATCH1, r11
 #ifdef CONFIG_403GCX
         stw     r12, 0(r0)
         stw     r9, 4(r0)
@@ -576,12 +576,12 @@ label:
         stw     r11, 8(r0)
         stw     r12, 12(r0)
 #else
-        mtspr   SPRN_SPRG4, r12
-        mtspr   SPRN_SPRG5, r9
+        mtspr   SPRN_SPRG_SCRATCH3, r12
+        mtspr   SPRN_SPRG_SCRATCH4, r9
         mfcr    r11
         mfspr   r12, SPRN_PID
-        mtspr   SPRN_SPRG7, r11
-        mtspr   SPRN_SPRG6, r12
+        mtspr   SPRN_SPRG_SCRATCH6, r11
+        mtspr   SPRN_SPRG_SCRATCH5, r12
 #endif
         mfspr   r10, SPRN_SRR0          /* Get faulting address */
 
@@ -600,7 +600,7 @@ label:
         /* Get the PGD for the current thread.
          */
 3:
-        mfspr   r11,SPRN_SPRG3
+        mfspr   r11,SPRN_SPRG_THREAD
         lwz     r11,PGDIR(r11)
 4:
         tophys(r11, r11)
@@ -650,15 +650,15 @@ label:
         lwz     r9, 4(r0)
         lwz     r12, 0(r0)
 #else
-        mfspr   r12, SPRN_SPRG6
-        mfspr   r11, SPRN_SPRG7
+        mfspr   r12, SPRN_SPRG_SCRATCH5
+        mfspr   r11, SPRN_SPRG_SCRATCH6
         mtspr   SPRN_PID, r12
         mtcr    r11
-        mfspr   r9, SPRN_SPRG5
-        mfspr   r12, SPRN_SPRG4
+        mfspr   r9, SPRN_SPRG_SCRATCH4
+        mfspr   r12, SPRN_SPRG_SCRATCH3
 #endif
-        mfspr   r11, SPRN_SPRG1
-        mfspr   r10, SPRN_SPRG0
+        mfspr   r11, SPRN_SPRG_SCRATCH1
+        mfspr   r10, SPRN_SPRG_SCRATCH0
         b       InstructionAccess
 
         EXCEPTION(0x1300, Trap_13, unknown_exception, EXC_XFER_EE)
@@ -803,15 +803,15 @@ finish_tlb_load:
         lwz     r9, 4(r0)
         lwz     r12, 0(r0)
 #else
-        mfspr   r12, SPRN_SPRG6
-        mfspr   r11, SPRN_SPRG7
+        mfspr   r12, SPRN_SPRG_SCRATCH5
+        mfspr   r11, SPRN_SPRG_SCRATCH6
         mtspr   SPRN_PID, r12
         mtcr    r11
-        mfspr   r9, SPRN_SPRG5
-        mfspr   r12, SPRN_SPRG4
+        mfspr   r9, SPRN_SPRG_SCRATCH4
+        mfspr   r12, SPRN_SPRG_SCRATCH3
 #endif
-        mfspr   r11, SPRN_SPRG1
-        mfspr   r10, SPRN_SPRG0
+        mfspr   r11, SPRN_SPRG_SCRATCH1
+        mfspr   r10, SPRN_SPRG_SCRATCH0
         PPC405_ERR77_SYNC
         rfi                     /* Should sync shadow TLBs */
         b       .               /* prevent prefetch past rfi */
@@ -835,7 +835,7 @@ start_here:
         /* 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
 
         /* stack */
         lis     r1,init_thread_union@ha