ARM: SMP: use more sane register allocation for __fixup_smp_on_up

Use r0,r3-r6 rather than r0,r3,r4,r6,r7, which makes it easier to
understand which registers can be modified.  Also document which
registers hold values which must be preserved.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 22 insertions, 17 deletions

diff --git a/arch/arm/kernel/head.S b/arch/arm/kernel/head.S
index dd6b369ac69..fd94e4e82fc 100644
--- a/arch/arm/kernel/head.S
+++ b/arch/arm/kernel/head.S
@@ -89,6 +89,11 @@ ENTRY(stext)
         bl      __lookup_machine_type           @ r5=machinfo
         movs    r8, r5                          @ invalid machine (r5=0)?
         beq     __error_a                       @ yes, error 'a'
+
+        /*
+         * r1 = machine no, r2 = atags,
+         * r8 = machinfo, r9 = cpuid, r10 = procinfo
+         */
         bl      __vet_atags
 #ifdef CONFIG_SMP_ON_UP
         bl      __fixup_smp
@@ -381,19 +386,19 @@ ENDPROC(__turn_mmu_on)
 
 #ifdef CONFIG_SMP_ON_UP
 __fixup_smp:
-        mov     r7, #0x00070000
-        orr     r6, r7, #0xff000000     @ mask 0xff070000
-        orr     r7, r7, #0x41000000     @ val 0x41070000
-        and     r0, r9, r6
-        teq     r0, r7                  @ ARM CPU and ARMv6/v7?
+        mov     r4, #0x00070000
+        orr     r3, r4, #0xff000000     @ mask 0xff070000
+        orr     r4, r4, #0x41000000     @ val 0x41070000
+        and     r0, r9, r3
+        teq     r0, r4                  @ ARM CPU and ARMv6/v7?
         bne     __fixup_smp_on_up       @ no, assume UP
 
-        orr     r6, r6, #0x0000ff00
-        orr     r6, r6, #0x000000f0     @ mask 0xff07fff0
-        orr     r7, r7, #0x0000b000
-        orr     r7, r7, #0x00000020     @ val 0x4107b020
-        and     r0, r9, r6
-        teq     r0, r7                  @ ARM 11MPCore?
+        orr     r3, r3, #0x0000ff00
+        orr     r3, r3, #0x000000f0     @ mask 0xff07fff0
+        orr     r4, r4, #0x0000b000
+        orr     r4, r4, #0x00000020     @ val 0x4107b020
+        and     r0, r9, r3
+        teq     r0, r4                  @ ARM 11MPCore?
         moveq   pc, lr                  @ yes, assume SMP
 
         mrc     p15, 0, r0, c0, c0, 5   @ read MPIDR
@@ -402,13 +407,13 @@ __fixup_smp:
 
 __fixup_smp_on_up:
         adr     r0, 1f
-        ldmia   r0, {r3, r6, r7}
+        ldmia   r0, {r3 - r5}
         sub     r3, r0, r3
-        add     r6, r6, r3
-        add     r7, r7, r3
-2:      cmp     r6, r7
-        ldmia   r6!, {r0, r4}
-        strlo   r4, [r0, r3]
+        add     r4, r4, r3
+        add     r5, r5, r3
+2:      cmp     r4, r5
+        ldmia   r4!, {r0, r6}
+        strlo   r6, [r0, r3]
         blo     2b
         mov     pc, lr
 ENDPROC(__fixup_smp)