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>

3 files changed, 14 insertions, 4 deletions

diff --git a/arch/arm/common/bL_switcher.c b/arch/arm/common/bL_switcher.c
index 5774b6ea7ad5..f01c0ee0c87e 100644
--- a/arch/arm/common/bL_switcher.c
+++ b/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);
 
diff --git a/arch/arm/common/mcpm_entry.c b/arch/arm/common/mcpm_entry.c
index 1e361abc29eb..86fd60fefbc9 100644
--- a/arch/arm/common/mcpm_entry.c
+++ b/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)
diff --git a/arch/arm/include/asm/mcpm.h b/arch/arm/include/asm/mcpm.h
index 608516ebabfe..a5ff410dcdb6 100644
--- a/arch/arm/include/asm/mcpm.h
+++ b/arch/arm/include/asm/mcpm.h
@@ -54,6 +54,13 @@ void mcpm_set_early_poke(unsigned cpu, unsigned cluster,
  */
 
 /**
+ * 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
  *
  * @cpu: CPU number within given cluster