iommu/vt-d: Populate debugfs if IOMMUs are detected

Currently, the intel iommu debugfs directory(/sys/kernel/debug/iommu/intel)
gets populated only when DMA remapping is enabled (dmar_disabled = 0)
irrespective of whether interrupt remapping is enabled or not.

Instead, populate the intel iommu debugfs directory if any IOMMUs are
detected.

Cc: Dan Carpenter <[e-mail]>
Fixes: ee2636b8670b1 ("iommu/vt-d: Enable base Intel IOMMU debugfs support")
Signed-off-by: Megha Dey <[e-mail]>
Signed-off-by: Lu Baolu <[e-mail]>
Signed-off-by: Joerg Roedel <[e-mail]>

drivers/iommu/intel-iommu-debugfs.c

···
 {
 	struct dmar_drhd_unit *drhd;
 	struct intel_iommu *iommu;
+	u32 sts;
 
 	rcu_read_lock();
 	for_each_active_iommu(iommu, drhd) {
+		sts = dmar_readl(iommu->reg + DMAR_GSTS_REG);
+		if (!(sts & DMA_GSTS_TES)) {
+			seq_printf(m, "DMA Remapping is not enabled on %s\n",
+				   iommu->name);
+			continue;
+		}
 		root_tbl_walk(m, iommu);
 		seq_putc(m, '\n');
 	}
···
 	struct dmar_drhd_unit *drhd;
 	struct intel_iommu *iommu;
 	u64 irta;
+	u32 sts;
 
 	rcu_read_lock();
 	for_each_active_iommu(iommu, drhd) {
···
 		seq_printf(m, "Remapped Interrupt supported on IOMMU: %s\n",
 			   iommu->name);
 
-		if (iommu->ir_table) {
+		sts = dmar_readl(iommu->reg + DMAR_GSTS_REG);
+		if (iommu->ir_table && (sts & DMA_GSTS_IRES)) {
 			irta = virt_to_phys(iommu->ir_table->base);
 			seq_printf(m, " IR table address:%llx\n", irta);
 			ir_tbl_remap_entry_show(m, iommu);

drivers/iommu/intel-iommu.c

···
 
 	down_write(&dmar_global_lock);
 
+	if (!no_iommu)
+		intel_iommu_debugfs_init();
+
 	if (no_iommu || dmar_disabled) {
 		/*
 		 * We exit the function here to ensure IOMMU's remapping and
···
 	pr_info("Intel(R) Virtualization Technology for Directed I/O\n");
 
 	intel_iommu_enabled = 1;
-	intel_iommu_debugfs_init();
 
 	return 0;