powerpc/powermac: Convert to hotplug state machine

Install the callbacks via the state machine.
I assume here that the powermac has two CPUs and so only one can go up
or down at a time. The variable smp_core99_host_open is here to ensure
that we do not try to open or close the i2c host twice if something goes
wrong and we invoke the prepare or online callback twice due to
rollback.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: rt@linutronix.de
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: linuxppc-dev@lists.ozlabs.org
Link: http://lkml.kernel.org/r/20160818125731.27256-16-bigeasy@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

arch/powerpc/platforms/powermac/smp.c

@@ -852,37 +852,33 @@ static void smp_core99_setup_cpu(int cpu_nr)
 
 #ifdef CONFIG_PPC64
 #ifdef CONFIG_HOTPLUG_CPU
-static int smp_core99_cpu_notify(struct notifier_block *self,
-				 unsigned long action, void *hcpu)
+static unsigned int smp_core99_host_open;
+
+static int smp_core99_cpu_prepare(unsigned int cpu)
 {
 	int rc;
 
-	switch(action & ~CPU_TASKS_FROZEN) {
-	case CPU_UP_PREPARE:
-		/* Open i2c bus if it was used for tb sync */
-		if (pmac_tb_clock_chip_host) {
-			rc = pmac_i2c_open(pmac_tb_clock_chip_host, 1);
-			if (rc) {
-				pr_err("Failed to open i2c bus for time sync\n");
-				return notifier_from_errno(rc);
-			}
+	/* Open i2c bus if it was used for tb sync */
+	if (pmac_tb_clock_chip_host && !smp_core99_host_open) {
+		rc = pmac_i2c_open(pmac_tb_clock_chip_host, 1);
+		if (rc) {
+			pr_err("Failed to open i2c bus for time sync\n");
+			return notifier_from_errno(rc);
 		}
-		break;
-	case CPU_ONLINE:
-	case CPU_UP_CANCELED:
-		/* Close i2c bus if it was used for tb sync */
-		if (pmac_tb_clock_chip_host)
-			pmac_i2c_close(pmac_tb_clock_chip_host);
-		break;
-	default:
-		break;
+		smp_core99_host_open = 1;
 	}
-	return NOTIFY_OK;
+	return 0;
 }
 
-static struct notifier_block smp_core99_cpu_nb = {
-	.notifier_call	= smp_core99_cpu_notify,
-};
+static int smp_core99_cpu_online(unsigned int cpu)
+{
+	/* Close i2c bus if it was used for tb sync */
+	if (pmac_tb_clock_chip_host && smp_core99_host_open) {
+		pmac_i2c_close(pmac_tb_clock_chip_host);
+		smp_core99_host_open = 0;
+	}
+	return 0;
+}
 #endif /* CONFIG_HOTPLUG_CPU */
 
 static void __init smp_core99_bringup_done(void)
@@ -902,7 +898,11 @@ static void __init smp_core99_bringup_done(void)
 		g5_phy_disable_cpu1();
 	}
 #ifdef CONFIG_HOTPLUG_CPU
-	register_cpu_notifier(&smp_core99_cpu_nb);
+	cpuhp_setup_state_nocalls(CPUHP_POWERPC_PMAC_PREPARE,
+				  "powerpc/pmac:prepare", smp_core99_cpu_prepare,
+				  NULL);
+	cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN, "powerpc/pmac:online",
+				  smp_core99_cpu_online, NULL);
 #endif
 
 	if (ppc_md.progress)

include/linux/cpuhotplug.h

@@ -31,6 +31,7 @@ enum cpuhp_state {
 	CPUHP_MD_RAID5_PREPARE,
 	CPUHP_RCUTREE_PREP,
 	CPUHP_CPUIDLE_COUPLED_PREPARE,
+	CPUHP_POWERPC_PMAC_PREPARE,
 	CPUHP_NOTIFY_PREPARE,
 	CPUHP_TIMERS_DEAD,
 	CPUHP_BRINGUP_CPU,