ARM: pm: allow suspend finisher to return error codes

There are SoCs where attempting to enter a low power state is ignored,
and the CPU continues executing instructions with all state preserved.
It is over-complex at that point to disable the MMU just to call the
resume path.

Instead, allow the suspend finisher to return error codes to abort
suspend in this circumstance, where the cpu_suspend internals will then
unwind the saved state on the stack.  Also omit the tlb flush as no
changes to the page tables will have happened.

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

1 files changed, 9 insertions, 2 deletions

diff --git a/arch/arm/kernel/sleep.S b/arch/arm/kernel/sleep.S
index c156d0e5f455..dc902f2c6845 100644
--- a/arch/arm/kernel/sleep.S
+++ b/arch/arm/kernel/sleep.S
@@ -12,7 +12,6 @@
  *  r1 = v:p offset
  *  r2 = suspend function arg0
  *  r3 = suspend function
- * Note: does not return until system resumes
  */
 ENTRY(__cpu_suspend)
         stmfd   sp!, {r4 - r11, lr}
@@ -26,7 +25,7 @@ ENTRY(__cpu_suspend)
 #endif
         mov     r6, sp                  @ current virtual SP
         sub     sp, sp, r5              @ allocate CPU state on stack
-        mov     r0, sp                  @ save pointer
+        mov     r0, sp                  @ save pointer to CPU save block
         add     ip, ip, r1              @ convert resume fn to phys
         stmfd   sp!, {r1, r6, ip}       @ save v:p, virt SP, phys resume fn
         ldr     r5, =sleep_save_sp
@@ -55,10 +54,17 @@ ENTRY(__cpu_suspend)
 #else
         bl      __cpuc_flush_kern_all
 #endif
+        adr     lr, BSYM(cpu_suspend_abort)
         ldmfd   sp!, {r0, pc}           @ call suspend fn
 ENDPROC(__cpu_suspend)
         .ltorg
 
+cpu_suspend_abort:
+        ldmia   sp!, {r1 - r3}          @ pop v:p, virt SP, phys resume fn
+        mov     sp, r2
+        ldmfd   sp!, {r4 - r11, pc}
+ENDPROC(cpu_suspend_abort)
+
 /*
  * r0 = control register value
  * r1 = v:p offset (preserved by cpu_do_resume)
@@ -89,6 +95,7 @@ cpu_resume_after_mmu:
         str     r5, [r2, r4, lsl #2]    @ restore old mapping
         mcr     p15, 0, r0, c1, c0, 0   @ turn on D-cache
         bl      cpu_init                @ restore the und/abt/irq banked regs
+        mov     r0, #0                  @ return zero on success
         ldmfd   sp!, {r4 - r11, pc}
 ENDPROC(cpu_resume_after_mmu)