irqchip/gic-v4.1: Don't use the VPE proxy if RVPEID is set

The infamous VPE proxy device isn't used with GICv4.1 because:
- we can invalidate any LPI from the DirectLPI MMIO interface
- the ITS and redistributors understand the life cycle of
  the doorbell, so we don't need to enable/disable it all
  the time

So let's escape early from the proxy related functions.
Signed-off-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Zenghui Yu <yuzenghui@huawei.com>
Link: https://lore.kernel.org/r/20191224111055.11836-8-maz@kernel.org

drivers/irqchip/irq-gic-v3-its.c

@@ -3212,7 +3212,7 @@ static const struct irq_domain_ops its_domain_ops = {
 /*
  * This is insane.
  *
- * If a GICv4 doesn't implement Direct LPIs (which is extremely
+ * If a GICv4.0 doesn't implement Direct LPIs (which is extremely
  * likely), the only way to perform an invalidate is to use a fake
  * device to issue an INV command, implying that the LPI has first
  * been mapped to some event on that device. Since this is not exactly
@@ -3220,9 +3220,20 @@ static const struct irq_domain_ops its_domain_ops = {
  * only issue an UNMAP if we're short on available slots.
  *
  * Broken by design(tm).
+ *
+ * GICv4.1, on the other hand, mandates that we're able to invalidate
+ * by writing to a MMIO register. It doesn't implement the whole of
+ * DirectLPI, but that's good enough. And most of the time, we don't
+ * even have to invalidate anything, as the redistributor can be told
+ * whether to generate a doorbell or not (we thus leave it enabled,
+ * always).
  */
 static void its_vpe_db_proxy_unmap_locked(struct its_vpe *vpe)
 {
+	/* GICv4.1 doesn't use a proxy, so nothing to do here */
+	if (gic_rdists->has_rvpeid)
+		return;
+
 	/* Already unmapped? */
 	if (vpe->vpe_proxy_event == -1)
 		return;
@@ -3245,6 +3256,10 @@ static void its_vpe_db_proxy_unmap_locked(struct its_vpe *vpe)
 
 static void its_vpe_db_proxy_unmap(struct its_vpe *vpe)
 {
+	/* GICv4.1 doesn't use a proxy, so nothing to do here */
+	if (gic_rdists->has_rvpeid)
+		return;
+
 	if (!gic_rdists->has_direct_lpi) {
 		unsigned long flags;
 
@@ -3256,6 +3271,10 @@ static void its_vpe_db_proxy_unmap(struct its_vpe *vpe)
 
 static void its_vpe_db_proxy_map_locked(struct its_vpe *vpe)
 {
+	/* GICv4.1 doesn't use a proxy, so nothing to do here */
+	if (gic_rdists->has_rvpeid)
+		return;
+
 	/* Already mapped? */
 	if (vpe->vpe_proxy_event != -1)
 		return;
@@ -3278,6 +3297,10 @@ static void its_vpe_db_proxy_move(struct its_vpe *vpe, int from, int to)
 	unsigned long flags;
 	struct its_collection *target_col;
 
+	/* GICv4.1 doesn't use a proxy, so nothing to do here */
+	if (gic_rdists->has_rvpeid)
+		return;
+
 	if (gic_rdists->has_direct_lpi) {
 		void __iomem *rdbase;