iommu/arm-smmu-v3: Add support for PCI PASID

Enable PASID for PCI devices that support it. Initialize PASID early in
add_device() because it must be enabled before ATS.
Tested-by: Zhangfei Gao <zhangfei.gao@linaro.org>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Signed-off-by: Will Deacon <will@kernel.org>

drivers/iommu/arm-smmu-v3.c

@@ -2628,6 +2628,53 @@ static void arm_smmu_disable_ats(struct arm_smmu_master *master)
 	atomic_dec(&smmu_domain->nr_ats_masters);
 }
 
+static int arm_smmu_enable_pasid(struct arm_smmu_master *master)
+{
+	int ret;
+	int features;
+	int num_pasids;
+	struct pci_dev *pdev;
+
+	if (!dev_is_pci(master->dev))
+		return -ENODEV;
+
+	pdev = to_pci_dev(master->dev);
+
+	features = pci_pasid_features(pdev);
+	if (features < 0)
+		return features;
+
+	num_pasids = pci_max_pasids(pdev);
+	if (num_pasids <= 0)
+		return num_pasids;
+
+	ret = pci_enable_pasid(pdev, features);
+	if (ret) {
+		dev_err(&pdev->dev, "Failed to enable PASID\n");
+		return ret;
+	}
+
+	master->ssid_bits = min_t(u8, ilog2(num_pasids),
+				  master->smmu->ssid_bits);
+	return 0;
+}
+
+static void arm_smmu_disable_pasid(struct arm_smmu_master *master)
+{
+	struct pci_dev *pdev;
+
+	if (!dev_is_pci(master->dev))
+		return;
+
+	pdev = to_pci_dev(master->dev);
+
+	if (!pdev->pasid_enabled)
+		return;
+
+	master->ssid_bits = 0;
+	pci_disable_pasid(pdev);
+}
+
 static void arm_smmu_detach_dev(struct arm_smmu_master *master)
 {
 	unsigned long flags;
@@ -2831,13 +2878,23 @@ static int arm_smmu_add_device(struct device *dev)
 
 	master->ssid_bits = min(smmu->ssid_bits, fwspec->num_pasid_bits);
 
+	/*
+	 * Note that PASID must be enabled before, and disabled after ATS:
+	 * PCI Express Base 4.0r1.0 - 10.5.1.3 ATS Control Register
+	 *
+	 *   Behavior is undefined if this bit is Set and the value of the PASID
+	 *   Enable, Execute Requested Enable, or Privileged Mode Requested bits
+	 *   are changed.
+	 */
+	arm_smmu_enable_pasid(master);
+
 	if (!(smmu->features & ARM_SMMU_FEAT_2_LVL_CDTAB))
 		master->ssid_bits = min_t(u8, master->ssid_bits,
 					  CTXDESC_LINEAR_CDMAX);
 
 	ret = iommu_device_link(&smmu->iommu, dev);
 	if (ret)
-		goto err_free_master;
+		goto err_disable_pasid;
 
 	group = iommu_group_get_for_dev(dev);
 	if (IS_ERR(group)) {
@@ -2850,6 +2907,8 @@ static int arm_smmu_add_device(struct device *dev)
 
 err_unlink:
 	iommu_device_unlink(&smmu->iommu, dev);
+err_disable_pasid:
+	arm_smmu_disable_pasid(master);
 err_free_master:
 	kfree(master);
 	fwspec->iommu_priv = NULL;
@@ -2870,6 +2929,7 @@ static void arm_smmu_remove_device(struct device *dev)
 	arm_smmu_detach_dev(master);
 	iommu_group_remove_device(dev);
 	iommu_device_unlink(&smmu->iommu, dev);
+	arm_smmu_disable_pasid(master);
 	kfree(master);
 	iommu_fwspec_free(dev);
 }