.notifier_call = mvebu_hwcc_platform_notifier,
};
+/*
+ * Keep track of whether we have IO hardware coherency enabled or not.
+ * On Armada 370's we will not be using it for example. We need to make
+ * that available [through coherency_available()] so the mbus controller
+ * doesn't enable the IO coherency bit in the attribute bits of the
+ * chip selects.
+ */
+static int coherency_enabled;
+
+int coherency_available(void)
+{
+ return coherency_enabled;
+}
+
int __init coherency_init(void)
{
struct device_node *np;
+ /*
+ * The coherency fabric is needed:
+ * - For coherency between processors on Armada XP, so only
+ * when SMP is enabled.
+ * - For coherency between the processor and I/O devices, but
+ * this coherency requires many pre-requisites (write
+ * allocate cache policy, shareable pages, SMP bit set) that
+ * are only meant in SMP situations.
+ *
+ * Note that this means that on Armada 370, there is currently
+ * no way to use hardware I/O coherency, because even when
+ * CONFIG_SMP is enabled, is_smp() returns false due to the
+ * Armada 370 being a single-core processor. To lift this
+ * limitation, we would have to find a way to make the cache
+ * policy set to write-allocate (on all Armada SoCs), and to
+ * set the shareable attribute in page tables (on all Armada
+ * SoCs except the Armada 370). Unfortunately, such decisions
+ * are taken very early in the kernel boot process, at a point
+ * where we don't know yet on which SoC we are running.
+ */
+ if (!is_smp())
+ return 0;
+
np = of_find_matching_node(NULL, of_coherency_table);
if (np) {
pr_info("Initializing Coherency fabric\n");
coherency_base = of_iomap(np, 0);
coherency_cpu_base = of_iomap(np, 1);
set_cpu_coherent(cpu_logical_map(smp_processor_id()), 0);
+ coherency_enabled = 1;
bus_register_notifier(&platform_bus_type,
&mvebu_hwcc_platform_nb);
}