iommu: Add IOMMU uclass

This uclass is intended to manage IOMMUs on systems where the
IOMMUs are not in bypass mode by default.  In that case U-Boot
cannot ignore the IOMMUs if it wants to use devices that need
to do DMA and sit behind such an IOMMU.

This initial IOMMU uclass implementation does not implement and
device ops and is intended for IOMMUs that have a bypass mode
that does not require address translation.  Support for IOMMUs
that do require address translation is planned and device ops
will be defined when support for such IOMMUs will be added.

Signed-off-by: Mark Kettenis <kettenis@openbsd.org>
Reviewed-by: Simon Glass <sjg@chromium.org>

1 files changed, 45 insertions, 0 deletions

diff --git a/drivers/iommu/iommu-uclass.c b/drivers/iommu/iommu-uclass.c
new file mode 100644
index 00000000000..ed917b3c3e8
--- /dev/null
+++ b/drivers/iommu/iommu-uclass.c
@@ -0,0 +1,45 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2021 Mark Kettenis <kettenis@openbsd.org>
+ */
+
+#define LOG_CATEGORY UCLASS_IOMMU
+
+#include <common.h>
+#include <dm.h>
+
+#if (CONFIG_IS_ENABLED(OF_CONTROL) && !CONFIG_IS_ENABLED(OF_PLATDATA))
+int dev_iommu_enable(struct udevice *dev)
+{
+	struct ofnode_phandle_args args;
+	struct udevice *dev_iommu;
+	int i, count, ret = 0;
+
+	count = dev_count_phandle_with_args(dev, "iommus",
+					    "#iommu-cells", 0);
+	for (i = 0; i < count; i++) {
+		ret = dev_read_phandle_with_args(dev, "iommus",
+						 "#iommu-cells", 0, i, &args);
+		if (ret) {
+			debug("%s: dev_read_phandle_with_args failed: %d\n",
+			      __func__, ret);
+			return ret;
+		}
+
+		ret = uclass_get_device_by_ofnode(UCLASS_IOMMU, args.node,
+						  &dev_iommu);
+		if (ret) {
+			debug("%s: uclass_get_device_by_ofnode failed: %d\n",
+			      __func__, ret);
+			return ret;
+		}
+	}
+
+	return 0;
+}
+#endif
+
+UCLASS_DRIVER(iommu) = {
+	.id		= UCLASS_IOMMU,
+	.name		= "iommu",
+};