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>

diff --git a/arch/arm/kernel/head.S b/arch/arm/kernel/head.S
index dd6b369..fd94e4e 100644 (file)
--- 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)