sparc: Use generic idle loop

Add generic cpu_idle support

sparc32:
- replace call to cpu_idle() with cpu_startup_entry()
- add arch_cpu_idle()

sparc64:
- smp_callin() now include cpu_startup_entry() call so we can
  skip calling cpu_idle from assembler
- add arch_cpu_idle() and arch_cpu_idle_dead()

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Reviewed-by: "Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com>
Cc: torvalds@linux-foundation.org
Cc: rusty@rustcorp.com.au
Cc: paulmck@linux.vnet.ibm.com
Cc: peterz@infradead.org
Cc: magnus.damm@gmail.com
Acked-by: David Miller <davem@davemloft.net>
Link: http://lkml.kernel.org/r/20130411193850.GA2330@merkur.ravnborg.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

arch/sparc/Kconfig

@@ -37,6 +37,7 @@ config SPARC
 	select GENERIC_SMP_IDLE_THREAD
 	select GENERIC_CMOS_UPDATE
 	select GENERIC_CLOCKEVENTS
+	select GENERIC_IDLE_LOOP
 	select GENERIC_STRNCPY_FROM_USER
 	select GENERIC_STRNLEN_USER
 	select MODULES_USE_ELF_RELA

arch/sparc/kernel/hvtramp.S

@@ -128,8 +128,7 @@ hv_cpu_startup:
 
 	call		smp_callin
 	 nop
-	call		cpu_idle
-	 mov		0, %o0
+
 	call		cpu_panic
 	 nop
 

arch/sparc/kernel/process_32.c

@@ -64,23 +64,12 @@ extern void fpsave(unsigned long *, unsigned long *, void *, unsigned long *);
 struct task_struct *last_task_used_math = NULL;
 struct thread_info *current_set[NR_CPUS];
 
-/*
- * the idle loop on a Sparc... ;)
- */
-void cpu_idle(void)
+/* Idle loop support. */
+void arch_cpu_idle(void)
 {
-	set_thread_flag(TIF_POLLING_NRFLAG);
-
-	/* endless idle loop with no priority at all */
-	for (;;) {
-		while (!need_resched()) {
-			if (sparc_idle)
-				(*sparc_idle)();
-			else
-				cpu_relax();
-		}
-		schedule_preempt_disabled();
-	}
+	if (sparc_idle)
+		(*sparc_idle)();
+	local_irq_enable();
 }
 
 /* XXX cli/sti -> local_irq_xxx here, check this works once SMP is fixed. */

arch/sparc/kernel/process_64.c

@@ -52,28 +52,25 @@
 
 #include "kstack.h"
 
-static void sparc64_yield(int cpu)
+/* Idle loop support on sparc64. */
+void arch_cpu_idle(void)
 {
 	if (tlb_type != hypervisor) {
 		touch_nmi_watchdog();
-		return;
-	}
-
-	clear_thread_flag(TIF_POLLING_NRFLAG);
-	smp_mb__after_clear_bit();
-
-	while (!need_resched() && !cpu_is_offline(cpu)) {
+	} else {
 		unsigned long pstate;
 
-		/* Disable interrupts. */
+                /* The sun4v sleeping code requires that we have PSTATE.IE cleared over
+                 * the cpu sleep hypervisor call.
+                 */
 		__asm__ __volatile__(
 			"rdpr %%pstate, %0\n\t"
 			"andn %0, %1, %0\n\t"
 			"wrpr %0, %%g0, %%pstate"
 			: "=&r" (pstate)
 			: "i" (PSTATE_IE));
 
-		if (!need_resched() && !cpu_is_offline(cpu))
+		if (!need_resched() && !cpu_is_offline(smp_processor_id()))
 			sun4v_cpu_yield();
 
 		/* Re-enable interrupts. */
@@ -84,36 +81,16 @@ static void sparc64_yield(int cpu)
 			: "=&r" (pstate)
 			: "i" (PSTATE_IE));
 	}
-
-	set_thread_flag(TIF_POLLING_NRFLAG);
+	local_irq_enable();
 }
 
-/* The idle loop on sparc64. */
-void cpu_idle(void)
-{
-	int cpu = smp_processor_id();
-
-	set_thread_flag(TIF_POLLING_NRFLAG);
-
-	while(1) {
-		tick_nohz_idle_enter();
-		rcu_idle_enter();
-
-		while (!need_resched() && !cpu_is_offline(cpu))
-			sparc64_yield(cpu);
-
-		rcu_idle_exit();
-		tick_nohz_idle_exit();
-
 #ifdef CONFIG_HOTPLUG_CPU
-		if (cpu_is_offline(cpu)) {
-			sched_preempt_enable_no_resched();
-			cpu_play_dead();
-		}
-#endif
-		schedule_preempt_disabled();
-	}
+void arch_cpu_idle_dead()
+{
+	sched_preempt_enable_no_resched();
+	cpu_play_dead();
 }
+#endif
 
 #ifdef CONFIG_COMPAT
 static void show_regwindow32(struct pt_regs *regs)

arch/sparc/kernel/smp_32.c

@@ -369,7 +369,7 @@ void __cpuinit sparc_start_secondary(void *arg)
 	local_irq_enable();
 
 	wmb();
-	cpu_idle();
+	cpu_startup_entry(CPUHP_ONLINE);
 
 	/* We should never reach here! */
 	BUG();

arch/sparc/kernel/smp_64.c

@@ -127,6 +127,8 @@ void __cpuinit smp_callin(void)
 
 	/* idle thread is expected to have preempt disabled */
 	preempt_disable();
+
+	cpu_startup_entry(CPUHP_ONLINE);
 }
 
 void cpu_panic(void)

arch/sparc/kernel/trampoline_64.S

@@ -407,8 +407,7 @@ after_lock_tlb:
 
 	call		smp_callin
 	 nop
-	call		cpu_idle
-	 mov		0, %o0
+
 	call		cpu_panic
 	 nop
 1:	b,a,pt		%xcc, 1b