AT91: pm: make sure that r0 is 0 when dealing with cache operations

When using CP15 cache operations (c7), we make sure that Rd (r0)
is actually 0 as ARM 926 TRM is saying.
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>

arch/arm/mach-at91/pm.c

@@ -261,8 +261,13 @@ static int at91_pm_enter(suspend_state_t state)
 			 * For ARM 926 based chips, this requirement is weaker
 			 * as at91sam9 can access a RAM in self-refresh mode.
 			 */
-			asm("b 1f; .align 5; 1:");
-			asm("mcr p15, 0, r0, c7, c10, 4");	/* drain write buffer */
+			asm volatile (	"mov r0, #0\n\t"
+					"b 1f\n\t"
+					".align 5\n\t"
+					"1: mcr p15, 0, r0, c7, c10, 4\n\t"
+					: /* no output */
+					: /* no input */
+					: "r0");
 			saved_lpr = sdram_selfrefresh_enable();
 			wait_for_interrupt_enable();
 			sdram_selfrefresh_disable(saved_lpr);

arch/arm/mach-at91/pm.h

@@ -21,7 +21,8 @@ static inline u32 sdram_selfrefresh_enable(void)
 }
 
 #define sdram_selfrefresh_disable(saved_lpr)	at91_sys_write(AT91_SDRAMC_LPR, saved_lpr)
-#define wait_for_interrupt_enable()		asm("mcr p15, 0, r0, c7, c0, 4")
+#define wait_for_interrupt_enable()		asm volatile ("mcr p15, 0, %0, c7, c0, 4" \
+								: : "r" (0))
 
 #elif defined(CONFIG_ARCH_AT91CAP9)
 #include <mach/at91cap9_ddrsdr.h>

arch/arm/mach-at91/pm_slowclock.S

@@ -124,6 +124,7 @@ ENTRY(at91_slow_clock)
 	ldr	r5, .at91_va_base_ramc1
 
 	/* Drain write buffer */
+	mov	r0, #0
 	mcr	p15, 0, r0, c7, c10, 4
 
 #ifdef CONFIG_ARCH_AT91RM9200