ARM: mvebu: add a coherency_available() call

This commit extends the coherency fabric code to provide a
coherency_available()function that the SoC code can call to be told
whether coherency support is available or not. On Armada 370/XP,
coherency support is available as soon as the relevant DT node is
present. On some upcoming SoCs, the DT node needs to be present *and*
the system running with CONFIG_SMP enabled.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Link: https://lkml.kernel.org/r/1397483228-25625-3-git-send-email-thomas.petazzoni@free-electrons.com
Signed-off-by: Jason Cooper <jason@lakedaemon.net>

arch/arm/mach-mvebu/coherency.c

@@ -39,6 +39,7 @@ static void __iomem *coherency_cpu_base;
 #define IO_SYNC_BARRIER_CTL_OFFSET		   0x0
 
 enum {
+	COHERENCY_FABRIC_TYPE_NONE,
 	COHERENCY_FABRIC_TYPE_ARMADA_370_XP,
 };
 
@@ -144,7 +145,7 @@ static void __init armada_370_coherency_init(struct device_node *np)
 	set_cpu_coherent(cpu_logical_map(smp_processor_id()), 0);
 }
 
-int __init coherency_init(void)
+static int coherency_type(void)
 {
 	struct device_node *np;
 
@@ -155,27 +156,40 @@ int __init coherency_init(void)
 		int type;
 
 		type = (int) match->data;
-		pr_info("Initializing Coherency fabric\n");
 
+		/* Armada 370/XP coherency works in both UP and SMP */
 		if (type == COHERENCY_FABRIC_TYPE_ARMADA_370_XP)
-			armada_370_coherency_init(np);
+			return type;
 
 		of_node_put(np);
 	}
 
-	return 0;
+	return COHERENCY_FABRIC_TYPE_NONE;
 }
 
-static int __init coherency_late_init(void)
+int coherency_available(void)
 {
+	return coherency_type() != COHERENCY_FABRIC_TYPE_NONE;
+}
+
+int __init coherency_init(void)
+{
+	int type = coherency_type();
 	struct device_node *np;
 
 	np = of_find_matching_node(NULL, of_coherency_table);
-	if (np) {
+
+	if (type == COHERENCY_FABRIC_TYPE_ARMADA_370_XP)
+		armada_370_coherency_init(np);
+
+	return 0;
+}
+
+static int __init coherency_late_init(void)
+{
+	if (coherency_available())
 		bus_register_notifier(&platform_bus_type,
 				      &mvebu_hwcc_platform_nb);
-		of_node_put(np);
-	}
 	return 0;
 }
 

arch/arm/mach-mvebu/coherency.h

@@ -18,5 +18,6 @@ extern unsigned long coherency_phys_base;
 
 int set_cpu_coherent(unsigned int cpu_id, int smp_group_id);
 int coherency_init(void);
+int coherency_available(void);
 
 #endif	/* __MACH_370_XP_COHERENCY_H */