powerpc/of: Remove useless register save/restore when calling OF back

enter_prom() used to save and restore registers such as CTR, XER etc..
which are volatile, or SRR0,1... which we don't care about. This
removes a bunch of useless code and while at it turns an mtmsrd into
an MTMSRD macro which will be useful to Book3E.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

1 files changed, 6 insertions, 32 deletions

diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
index dbf0e3115611..1cb0f3d1714b 100644
--- a/arch/powerpc/kernel/entry_64.S
+++ b/arch/powerpc/kernel/entry_64.S
@@ -823,30 +823,17 @@ _GLOBAL(enter_prom)
          * of all registers that it saves.  We therefore save those registers
          * PROM might touch to the stack.  (r0, r3-r13 are caller saved)
          */
-        SAVE_8GPRS(2, r1)
+        SAVE_GPR(2, r1)
         SAVE_GPR(13, r1)
         SAVE_8GPRS(14, r1)
         SAVE_10GPRS(22, r1)
-        mfcr    r4
-        std     r4,_CCR(r1)
-        mfctr   r5
-        std     r5,_CTR(r1)
-        mfspr   r6,SPRN_XER
-        std     r6,_XER(r1)
-        mfdar   r7
-        std     r7,_DAR(r1)
-        mfdsisr r8
-        std     r8,_DSISR(r1)
-        mfsrr0  r9
-        std     r9,_SRR0(r1)
-        mfsrr1  r10
-        std     r10,_SRR1(r1)
+        mfcr    r10
         mfmsr   r11
+        std     r10,_CCR(r1)
         std     r11,_MSR(r1)
 
         /* Get the PROM entrypoint */
-        ld      r0,GPR4(r1)
-        mtlr    r0
+        mtlr    r4
 
         /* Switch MSR to 32 bits mode
          */
@@ -860,8 +847,7 @@ _GLOBAL(enter_prom)
         mtmsrd  r11
         isync
 
-        /* Restore arguments & enter PROM here... */
-        ld      r3,GPR3(r1)
+        /* Enter PROM here... */
         blrl
 
         /* Just make sure that r1 top 32 bits didn't get
@@ -871,7 +857,7 @@ _GLOBAL(enter_prom)
 
         /* Restore the MSR (back to 64 bits) */
         ld      r0,_MSR(r1)
-        mtmsrd  r0
+        MTMSRD(r0)
         isync
 
         /* Restore other registers */
@@ -881,18 +867,6 @@ _GLOBAL(enter_prom)
         REST_10GPRS(22, r1)
         ld      r4,_CCR(r1)
         mtcr    r4
-        ld      r5,_CTR(r1)
-        mtctr   r5
-        ld      r6,_XER(r1)
-        mtspr   SPRN_XER,r6
-        ld      r7,_DAR(r1)
-        mtdar   r7
-        ld      r8,_DSISR(r1)
-        mtdsisr r8
-        ld      r9,_SRR0(r1)
-        mtsrr0  r9
-        ld      r10,_SRR1(r1)
-        mtsrr1  r10
         
         addi    r1,r1,PROM_FRAME_SIZE
         ld      r0,16(r1)