[ARM] pxa: skip registers saving/restoring if entering standby mode

registers are retained during standby mode, thus it's not necessary
to save/restore and checksum
Signed-off-by: eric miao <eric.miao@marvell.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/mach-pxa/pm.c

@@ -38,19 +38,22 @@ int pxa_pm_enter(suspend_state_t state)
 		iwmmxt_task_disable(NULL);
 #endif
 
+	/* skip registers saving for standby */
+	if (state != PM_SUSPEND_STANDBY) {
 		pxa_cpu_pm_fns->save(sleep_save);
-
-	/* Clear sleep reset status */
-	RCSR = RCSR_SMR;
-
 		/* before sleeping, calculate and save a checksum */
 		for (i = 0; i < pxa_cpu_pm_fns->save_size - 1; i++)
 			sleep_save_checksum += sleep_save[i];
+	}
+
+	/* Clear sleep reset status */
+	RCSR = RCSR_SMR;
 
 	/* *** go zzz *** */
 	pxa_cpu_pm_fns->enter(state);
 	cpu_init();
 
+	if (state != PM_SUSPEND_STANDBY) {
 		/* after sleeping, validate the checksum */
 		for (i = 0; i < pxa_cpu_pm_fns->save_size - 1; i++)
 			checksum += sleep_save[i];
@@ -63,8 +66,8 @@ int pxa_pm_enter(suspend_state_t state)
 			while (1)
 				pxa_cpu_pm_fns->enter(state);
 		}
-
 		pxa_cpu_pm_fns->restore(sleep_save);
+	}
 
 	pr_debug("*** made it back from resume\n");