iommu/omap: add support for late attachment of iommu devices

Current implementation of OMAP IOMMU enforces strict ordering of device
probe, initiated by iommu and followed by remoteproc later. This doesn't
work too well with the new setup done with ti-sysc changes which may
have the devices probed at pretty much any order. To overcome this limitation,
if iommu has not been probed yet when a consumer tries to attach to it,
add the device to orphan device list which will be parsed during iommu
probe to see if any orphan devices should be attached.

Signed-off-by: Tero Kristo <[e-mail]>
Signed-off-by: Joerg Roedel <[e-mail]>

drivers/iommu/omap-iommu.c

···
 
 static const struct iommu_ops omap_iommu_ops;
 
+struct orphan_dev {
+	struct device *dev;
+	struct list_head node;
+};
+
+static LIST_HEAD(orphan_dev_list);
+
+static DEFINE_SPINLOCK(orphan_lock);
+
 #define to_iommu(dev)	((struct omap_iommu *)dev_get_drvdata(dev))
 
 /* bitmap of the page sizes currently supported */
···
 
 static struct platform_driver omap_iommu_driver;
 static struct kmem_cache *iopte_cachep;
+
+static int _omap_iommu_add_device(struct device *dev);
 
 /**
  * to_omap_domain - Get struct omap_iommu_domain from generic iommu_domain
···
 	struct omap_iommu *obj;
 	struct resource *res;
 	struct device_node *of = pdev->dev.of_node;
+	struct orphan_dev *orphan_dev, *tmp;
 
 	if (!of) {
 		pr_err("%s: only DT-based devices are supported\n", __func__);
···
 	omap_iommu_debugfs_add(obj);
 
 	dev_info(&pdev->dev, "%s registered\n", obj->name);
+
+	list_for_each_entry_safe(orphan_dev, tmp, &orphan_dev_list, node) {
+		err = _omap_iommu_add_device(orphan_dev->dev);
+		if (!err) {
+			list_del(&orphan_dev->node);
+			kfree(orphan_dev);
+		}
+	}
 
 	return 0;
 
···
 	return ret;
 }
 
-static int omap_iommu_add_device(struct device *dev)
+static int _omap_iommu_add_device(struct device *dev)
 {
 	struct omap_iommu_arch_data *arch_data, *tmp;
 	struct omap_iommu *oiommu;
···
 	struct platform_device *pdev;
 	int num_iommus, i;
 	int ret;
+	struct orphan_dev *orphan_dev;
+	unsigned long flags;
 
 	/*
 	 * Allocate the archdata iommu structure for DT-based devices.
···
 		}
 
 		pdev = of_find_device_by_node(np);
-		if (WARN_ON(!pdev)) {
+		if (!pdev) {
 			of_node_put(np);
 			kfree(arch_data);
-			return -EINVAL;
+			spin_lock_irqsave(&orphan_lock, flags);
+			list_for_each_entry(orphan_dev, &orphan_dev_list,
+					    node) {
+				if (orphan_dev->dev == dev)
+					break;
+			}
+			spin_unlock_irqrestore(&orphan_lock, flags);
+
+			if (orphan_dev && orphan_dev->dev == dev)
+				return -EPROBE_DEFER;
+
+			orphan_dev = kzalloc(sizeof(*orphan_dev), GFP_KERNEL);
+			orphan_dev->dev = dev;
+			spin_lock_irqsave(&orphan_lock, flags);
+			list_add(&orphan_dev->node, &orphan_dev_list);
+			spin_unlock_irqrestore(&orphan_lock, flags);
+			return -EPROBE_DEFER;
 		}
 
 		oiommu = platform_get_drvdata(pdev);
···
 		}
 
 		tmp->iommu_dev = oiommu;
+		tmp->dev = &pdev->dev;
 
 		of_node_put(np);
 	}
···
 	iommu_group_put(group);
 
 	return 0;
+}
+
+static int omap_iommu_add_device(struct device *dev)
+{
+	int ret;
+
+	ret = _omap_iommu_add_device(dev);
+	if (ret == -EPROBE_DEFER)
+		return 0;
+
+	return ret;
 }
 
 static void omap_iommu_remove_device(struct device *dev)

drivers/iommu/omap-iommu.h

···
 
 /**
  * struct omap_iommu_arch_data - omap iommu private data
- * @iommu_dev: handle of the iommu device
+ * @iommu_dev: handle of the OMAP iommu device
+ * @dev: handle of the iommu device
  *
  * This is an omap iommu private data object, which binds an iommu user
  * to its iommu device. This object should be placed at the iommu user's
···
  */
 struct omap_iommu_arch_data {
 	struct omap_iommu *iommu_dev;
+	struct device *dev;
 };
 
 struct cr_regs {