ARM: 8032/1: bL_switcher: fix validation check before its activation

The switcher should not depend on MAX_CLUSTER to determine ifit should
be activated or not. In a multiplatform kernel binary it is possible to
have dual-cluster and quad-cluster platforms configured in. In that case
MAX_CLUSTER which is a build time limit should be 4 and that shouldn't
prevent the switcher from working if the kernel is booted on a b.L
dual-cluster system.

In bL_switcher_halve_cpus() we already have a runtime validation check
to make sure we're dealing with only two clusters, so booting on a quad
cluster system will be caught and switcher activation aborted.

However, the b.L switcher must ensure the MCPM layer is initialized on
the booted hardware before doing anything.  The mcpm_is_available()
function is added to that effect.
Signed-off-by: Nicolas Pitre <nico@linaro.org>
Tested-by: Abhilash Kesavan <kesavan.abhilash@gmail.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/common/bL_switcher.c

@@ -797,10 +797,8 @@ static int __init bL_switcher_init(void)
 {
 	int ret;
 
-	if (MAX_NR_CLUSTERS != 2) {
-		pr_err("%s: only dual cluster systems are supported\n", __func__);
-		return -EINVAL;
-	}
+	if (!mcpm_is_available())
+		return -ENODEV;
 
 	cpu_notifier(bL_switcher_hotplug_callback, 0);
 

arch/arm/common/mcpm_entry.c

@@ -48,6 +48,11 @@ int __init mcpm_platform_register(const struct mcpm_platform_ops *ops)
 	return 0;
 }
 
+bool mcpm_is_available(void)
+{
+	return (platform_ops) ? true : false;
+}
+
 int mcpm_cpu_power_up(unsigned int cpu, unsigned int cluster)
 {
 	if (!platform_ops)

arch/arm/include/asm/mcpm.h

@@ -53,6 +53,13 @@ void mcpm_set_early_poke(unsigned cpu, unsigned cluster,
  * CPU/cluster power operations API for higher subsystems to use.
  */
 
+/**
+ * mcpm_is_available - returns whether MCPM is initialized and available
+ *
+ * This returns true or false accordingly.
+ */
+bool mcpm_is_available(void);
+
 /**
  * mcpm_cpu_power_up - make given CPU in given cluster runable
  *