iommmu/of: Do not return struct iommu_ops from of_iommu_configure()

Nothing needs this pointer. Return a normal error code with the usual
IOMMU semantic that ENODEV means 'there is no IOMMU driver'.

Reviewed-by: Jerry Snitselaar <jsnitsel@redhat.com>
Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
Acked-by: Rob Herring <robh@kernel.org>
Tested-by: Hector Martin <marcan@marcan.st>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/2-v2-16e4def25ebb+820-iommu_fwspec_p1_jgg@nvidia.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>

Author: jgunthorpe

drivers/iommu/of_iommu.c

@@ -107,24 +107,30 @@ static int of_iommu_configure_device(struct device_node *master_np,
 		      of_iommu_configure_dev(master_np, dev);
 }
 
-const struct iommu_ops *of_iommu_configure(struct device *dev,
-					   struct device_node *master_np,
-					   const u32 *id)
+/*
+ * Returns:
+ *  0 on success, an iommu was configured
+ *  -ENODEV if the device does not have any IOMMU
+ *  -EPROBEDEFER if probing should be tried again
+ *  -errno fatal errors
+ */
+int of_iommu_configure(struct device *dev, struct device_node *master_np,
+		       const u32 *id)
 {
 	const struct iommu_ops *ops = NULL;
 	struct iommu_fwspec *fwspec;
 	int err = NO_IOMMU;
 
 	if (!master_np)
-		return NULL;
+		return -ENODEV;
 
 	/* Serialise to make dev->iommu stable under our potential fwspec */
 	mutex_lock(&iommu_probe_device_lock);
 	fwspec = dev_iommu_fwspec_get(dev);
 	if (fwspec) {
 		if (fwspec->ops) {
 			mutex_unlock(&iommu_probe_device_lock);
-			return fwspec->ops;
+			return 0;
 		}
 		/* In the deferred case, start again from scratch */
 		iommu_fwspec_free(dev);
@@ -169,14 +175,15 @@ const struct iommu_ops *of_iommu_configure(struct device *dev,
 		err = iommu_probe_device(dev);
 
 	/* Ignore all other errors apart from EPROBE_DEFER */
-	if (err == -EPROBE_DEFER) {
-		ops = ERR_PTR(err);
-	} else if (err < 0) {
-		dev_dbg(dev, "Adding to IOMMU failed: %d\n", err);
-		ops = NULL;
+	if (err < 0) {
+		if (err == -EPROBE_DEFER)
+			return err;
+		dev_dbg(dev, "Adding to IOMMU failed: %pe\n", ERR_PTR(err));
+		return err;
 	}
-
-	return ops;
+	if (!ops)
+		return -ENODEV;
+	return 0;
 }
 
 static enum iommu_resv_type __maybe_unused

drivers/of/device.c

@@ -93,12 +93,12 @@ of_dma_set_restricted_buffer(struct device *dev, struct device_node *np)
 int of_dma_configure_id(struct device *dev, struct device_node *np,
 			bool force_dma, const u32 *id)
 {
-	const struct iommu_ops *iommu;
 	const struct bus_dma_region *map = NULL;
 	struct device_node *bus_np;
 	u64 dma_start = 0;
 	u64 mask, end, size = 0;
 	bool coherent;
+	int iommu_ret;
 	int ret;
 
 	if (np == dev->of_node)
@@ -181,21 +181,29 @@ int of_dma_configure_id(struct device *dev, struct device_node *np,
 	dev_dbg(dev, "device is%sdma coherent\n",
 		coherent ? " " : " not ");
 
-	iommu = of_iommu_configure(dev, np, id);
-	if (PTR_ERR(iommu) == -EPROBE_DEFER) {
+	iommu_ret = of_iommu_configure(dev, np, id);
+	if (iommu_ret == -EPROBE_DEFER) {
 		/* Don't touch range map if it wasn't set from a valid dma-ranges */
 		if (!ret)
 			dev->dma_range_map = NULL;
 		kfree(map);
 		return -EPROBE_DEFER;
-	}
+	} else if (iommu_ret == -ENODEV) {
+		dev_dbg(dev, "device is not behind an iommu\n");
+	} else if (iommu_ret) {
+		dev_err(dev, "iommu configuration for device failed with %pe\n",
+			ERR_PTR(iommu_ret));
 
-	dev_dbg(dev, "device is%sbehind an iommu\n",
-		iommu ? " " : " not ");
+		/*
+		 * Historically this routine doesn't fail driver probing
+		 * due to errors in of_iommu_configure()
+		 */
+	} else
+		dev_dbg(dev, "device is behind an iommu\n");
 
 	arch_setup_dma_ops(dev, dma_start, size, coherent);
 
-	if (!iommu)
+	if (iommu_ret)
 		of_dma_set_restricted_buffer(dev, np);
 
 	return 0;

include/linux/of_iommu.h

@@ -8,20 +8,19 @@ struct iommu_ops;
 
 #ifdef CONFIG_OF_IOMMU
 
-extern const struct iommu_ops *of_iommu_configure(struct device *dev,
-					struct device_node *master_np,
-					const u32 *id);
+extern int of_iommu_configure(struct device *dev, struct device_node *master_np,
+			      const u32 *id);
 
 extern void of_iommu_get_resv_regions(struct device *dev,
 				      struct list_head *list);
 
 #else
 
-static inline const struct iommu_ops *of_iommu_configure(struct device *dev,
-					 struct device_node *master_np,
-					 const u32 *id)
+static inline int of_iommu_configure(struct device *dev,
+				     struct device_node *master_np,
+				     const u32 *id)
 {
-	return NULL;
+	return -ENODEV;
 }
 
 static inline void of_iommu_get_resv_regions(struct device *dev,