AT91: pm: use plain cpu_do_idle() for "wait for interrupt"

For power management at91_pm_enter() routine, use the cpu_do_idle() for a
rock solid "wait for interrupt" implementation.
For AT91SAM9 ARM 926 based chips, we can exceed the cache line length as
we can access RAM even while in self-refresh mode.
We keep plain access to CP15 for at91rm9200 as this feature is not
available: instructions have to be in a single cache line.

Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>

2 files changed, 8 insertions, 2 deletions

diff --git a/arch/arm/mach-at91/pm.c b/arch/arm/mach-at91/pm.c
index 615668986480..87a31baf1cb3 100644
--- a/arch/arm/mach-at91/pm.c
+++ b/arch/arm/mach-at91/pm.c
@@ -258,16 +258,18 @@ static int at91_pm_enter(suspend_state_t state)
                          * NOTE: the Wait-for-Interrupt instruction needs to be
                          * in icache so no SDRAM accesses are needed until the
                          * wakeup IRQ occurs and self-refresh is terminated.
+                         * 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 */
                         saved_lpr = sdram_selfrefresh_enable();
-                        asm("mcr p15, 0, r0, c7, c0, 4");       /* wait for interrupt */
+                        wait_for_interrupt_enable();
                         sdram_selfrefresh_disable(saved_lpr);
                         break;
 
                 case PM_SUSPEND_ON:
-                        asm("mcr p15, 0, r0, c7, c0, 4");       /* wait for interrupt */
+                        cpu_do_idle();
                         break;
 
                 default:
diff --git a/arch/arm/mach-at91/pm.h b/arch/arm/mach-at91/pm.h
index 8c87d0c1b8f8..2c4424bfa6c4 100644
--- a/arch/arm/mach-at91/pm.h
+++ b/arch/arm/mach-at91/pm.h
@@ -21,6 +21,7 @@ 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")
 
 #elif defined(CONFIG_ARCH_AT91CAP9)
 #include <mach/at91cap9_ddrsdr.h>
@@ -38,6 +39,7 @@ static inline u32 sdram_selfrefresh_enable(void)
 }
 
 #define sdram_selfrefresh_disable(saved_lpr)    at91_ramc_write(0, AT91_DDRSDRC_LPR, saved_lpr)
+#define wait_for_interrupt_enable()             cpu_do_idle()
 
 #elif defined(CONFIG_ARCH_AT91SAM9G45)
 #include <mach/at91sam9_ddrsdr.h>
@@ -74,6 +76,7 @@ static inline u32 sdram_selfrefresh_enable(void)
                 at91_ramc_write(0, AT91_DDRSDRC_LPR, saved_lpr0); \
                 at91_ramc_write(1, AT91_DDRSDRC_LPR, saved_lpr1); \
         } while (0)
+#define wait_for_interrupt_enable()             cpu_do_idle()
 
 #else
 #include <mach/at91sam9_sdramc.h>
@@ -98,5 +101,6 @@ static inline u32 sdram_selfrefresh_enable(void)
 }
 
 #define sdram_selfrefresh_disable(saved_lpr)    at91_ramc_write(0, AT91_SDRAMC_LPR, saved_lpr)
+#define wait_for_interrupt_enable()             cpu_do_idle()
 
 #endif