[PATCH 4/7] ARM: EXYNOS4: Support early wakeup while entering sleep mode

[linux@arm.linux.org.uk (Russell King - ARM Linux)]

On Fri, Jun 24, 2011 at 10:37:50AM +0100, Russell King - ARM Linux wrote:
> On Fri, Jun 24, 2011 at 04:42:26PM +0900, Kukjin Kim wrote:
> > Russell King - ARM Linux wrote:
> > 
> > > Stop bodging stuff (like you have for the SCU stuff.) and start _talking_
> > > to people if the code doesn't do what you need it to do.
> > 
> > Hi Russell and all,
> > 
> > I'd like to share requirement of EXYNOS4210 PM.
> > 
> > Now if there is wakeup source which is pending before entering suspend mode,
> > PMU(Power Management Unit) handles WFI instruction as NOP on EXYNOS4210. But
> > it seems that current cpu_suspend() cannot support this. So how can/should
> > we handle this case?
> 
> See patch from June 13th posted to the hibernate thread.  This allows
> the finisher function to return, though it should only return if it is
> certain that the system will not enter suspend.
> 
> Is this true of the current exynos4 code?  It seems that the current
> code will panic() if the WFI is executed as a NOP.

Here's an updated patch for it against the v3 set of patches.

 arch/arm/include/asm/suspend.h |    9 +++++----
 arch/arm/kernel/sleep.S        |   11 +++++++++--
 2 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/arch/arm/include/asm/suspend.h b/arch/arm/include/asm/suspend.h
index f8db9d0..54821b5 100644
--- a/arch/arm/include/asm/suspend.h
+++ b/arch/arm/include/asm/suspend.h
@@ -10,12 +10,13 @@ extern void cpu_resume(void);
  * Hide the first two arguments to __cpu_suspend - these are an implementation
  * detail which platform code shouldn't have to know about.
  */
-static inline void cpu_suspend(unsigned long arg, void (*fn)(unsigned long))
+static inline int cpu_suspend(unsigned long arg, void (*fn)(unsigned long))
 {
-	extern void __cpu_suspend(int, long, unsigned long,
-				  void (*)(unsigned long));
-	__cpu_suspend(0, PHYS_OFFSET - PAGE_OFFSET, arg, fn);
+	extern int __cpu_suspend(int, long, unsigned long,
+				 void (*)(unsigned long));
+	int ret = __cpu_suspend(0, PHYS_OFFSET - PAGE_OFFSET, arg, fn);
 	flush_tlb_all();
+	return ret;
 }
 
 #endif
diff --git a/arch/arm/kernel/sleep.S b/arch/arm/kernel/sleep.S
index c156d0e..dc902f2 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)