[PATCH v2 1/7] iommu: Add IOMMU uclass

[Mark Kettenis]

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 at openbsd.org>
---
 drivers/Kconfig              |  2 ++
 drivers/Makefile             |  1 +
 drivers/core/device.c        |  8 +++++++
 drivers/iommu/Kconfig        | 13 +++++++++++
 drivers/iommu/Makefile       |  3 +++
 drivers/iommu/iommu-uclass.c | 45 ++++++++++++++++++++++++++++++++++++
 include/dm/uclass-id.h       |  1 +
 include/iommu.h              | 16 +++++++++++++
 8 files changed, 89 insertions(+)
 create mode 100644 drivers/iommu/Kconfig
 create mode 100644 drivers/iommu/Makefile
 create mode 100644 drivers/iommu/iommu-uclass.c
 create mode 100644 include/iommu.h

diff --git a/drivers/Kconfig b/drivers/Kconfig
index 417d6f88c2..b26ca8cf70 100644
--- a/drivers/Kconfig
+++ b/drivers/Kconfig
@@ -50,6 +50,8 @@ source "drivers/i2c/Kconfig"
 
 source "drivers/input/Kconfig"
 
+source "drivers/iommu/Kconfig"
+
 source "drivers/led/Kconfig"
 
 source "drivers/mailbox/Kconfig"
diff --git a/drivers/Makefile b/drivers/Makefile
index fd218c9056..166aeb9817 100644
--- a/drivers/Makefile
+++ b/drivers/Makefile
@@ -109,6 +109,7 @@ obj-y += mtd/
 obj-y += pwm/
 obj-y += reset/
 obj-y += input/
+obj-y += iommu/
 # SOC specific infrastructure drivers.
 obj-y += smem/
 obj-y += thermal/
diff --git a/drivers/core/device.c b/drivers/core/device.c
index 29668f6fb3..5f480ad443 100644
--- a/drivers/core/device.c
+++ b/drivers/core/device.c
@@ -28,6 +28,7 @@
 #include <dm/uclass.h>
 #include <dm/uclass-internal.h>
 #include <dm/util.h>
+#include <iommu.h>
 #include <linux/err.h>
 #include <linux/list.h>
 #include <power-domain.h>
@@ -543,6 +544,13 @@ int device_probe(struct udevice *dev)
 			goto fail;
 	}
 
+	if (CONFIG_IS_ENABLED(IOMMU) && dev->parent &&
+	    (device_get_uclass_id(dev) != UCLASS_IOMMU)) {
+		ret = dev_iommu_probe(dev);
+		if (ret)
+			goto fail;
+	}
+
 	ret = device_get_dma_constraints(dev);
 	if (ret)
 		goto fail;
diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
new file mode 100644
index 0000000000..8cb377560e
--- /dev/null
+++ b/drivers/iommu/Kconfig
@@ -0,0 +1,13 @@
+#
+# IOMMU devices
+#
+
+menu "IOMMU device drivers"
+
+config IOMMU
+	bool "Enable Driver Model for IOMMU drivers"
+	depends on DM
+	help
+	  Enable driver model for IOMMU devices.
+
+endmenu
diff --git a/drivers/iommu/Makefile b/drivers/iommu/Makefile
new file mode 100644
index 0000000000..f1ceb10150
--- /dev/null
+++ b/drivers/iommu/Makefile
@@ -0,0 +1,3 @@
+# SPDX-License-Identifier: GPL-2.0+
+
+obj-$(CONFIG_IOMMU) += iommu-uclass.o
diff --git a/drivers/iommu/iommu-uclass.c b/drivers/iommu/iommu-uclass.c
new file mode 100644
index 0000000000..5c55df3066
--- /dev/null
+++ b/drivers/iommu/iommu-uclass.c
@@ -0,0 +1,45 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2021 Mark Kettenis <kettenis at 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_probe(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",
+};
diff --git a/include/dm/uclass-id.h b/include/dm/uclass-id.h
index e7edd409f3..56aa981613 100644
--- a/include/dm/uclass-id.h
+++ b/include/dm/uclass-id.h
@@ -61,6 +61,7 @@ enum uclass_id {
 	UCLASS_I2C_MUX,		/* I2C multiplexer */
 	UCLASS_I2S,		/* I2S bus */
 	UCLASS_IDE,		/* IDE device */
+	UCLASS_IOMMU,		/* IOMMU */
 	UCLASS_IRQ,		/* Interrupt controller */
 	UCLASS_KEYBOARD,	/* Keyboard input device */
 	UCLASS_LED,		/* Light-emitting diode (LED) */
diff --git a/include/iommu.h b/include/iommu.h
new file mode 100644
index 0000000000..d17a06a6f3
--- /dev/null
+++ b/include/iommu.h
@@ -0,0 +1,16 @@
+#ifndef _IOMMU_H
+#define _IOMMU_H
+
+struct udevice;
+
+#if (CONFIG_IS_ENABLED(OF_CONTROL) && !CONFIG_IS_ENABLED(OF_PLATDATA)) && \
+	CONFIG_IS_ENABLED(IOMMU)
+int dev_iommu_probe(struct udevice *dev);
+#else
+static inline int dev_iommu_probe(struct udevice *dev)
+{
+	return 0;
+}
+#endif
+
+#endif
-- 
2.33.0