ARM: 8389/1: Add cpu_resume_arm() for firmwares that resume in ARM state

Some platforms always enter the kernel in the ARM state even if
the kernel is compiled for THUMB2. Add a small wrapper on top of
cpu_resume() that switches into THUMB2 state.

This provides the functionality to fix a problem reported by Kevin
Hilman on next-20150601 where the ifc6410 fails to boot a THUMB2
kernel because the platform's firmware always enters the kernel in
ARM mode from deep idle states.

(rmk: tweaked to work without BSYM->badr changes.)

Reported-by: Kevin Hilman <khilman@linaro.org>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Lina Iyer <lina.iyer@linaro.org>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/include/asm/suspend.h

@@ -7,6 +7,7 @@ struct sleep_save_sp {
 };
 
 extern void cpu_resume(void);
+extern void cpu_resume_arm(void);
 extern int cpu_suspend(unsigned long, int (*)(unsigned long));
 
 #endif

arch/arm/kernel/sleep.S

@@ -118,6 +118,12 @@ ENDPROC(cpu_resume_after_mmu)
 
 	.text
 	.align
+	.arm
+ENTRY(cpu_resume_arm)
+ THUMB(	adr	r9, BSYM(1f)	)	@ Kernel is entered in ARM.
+ THUMB(	bx	r9		)	@ If this is a Thumb-2 kernel,
+ THUMB(	.thumb			)	@ switch to Thumb now.
+ THUMB(1:			)
 ENTRY(cpu_resume)
 ARM_BE8(setend be)			@ ensure we are in BE mode
 #ifdef CONFIG_ARM_VIRT_EXT
@@ -149,6 +155,7 @@ THUMB(	ldmia	r0!, {r1, r2, r3}	)
 THUMB(	mov	sp, r2			)
 THUMB(	bx	r3			)
 ENDPROC(cpu_resume)
+ENDPROC(cpu_resume_arm)
 
 	.align 2
 _sleep_save_sp: