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>
diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
index dbf0e31..1cb0f3d 100644
--- a/arch/powerpc/kernel/entry_64.S
+++ b/arch/powerpc/kernel/entry_64.S
@@ -823,30 +823,17 @@
* 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 @@
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 @@
/* Restore the MSR (back to 64 bits) */
ld r0,_MSR(r1)
- mtmsrd r0
+ MTMSRD(r0)
isync
/* Restore other registers */
@@ -881,18 +867,6 @@
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)
