[v2,1/3] ACPI: RISC-V: Add support for RIMT

diff --git a/MAINTAINERS b/MAINTAINERS
index a92290fffa16..9d36ad744af5 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -345,6 +345,7 @@  L:	linux-acpi@vger.kernel.org
 L:	linux-riscv@lists.infradead.org
 S:	Maintained
 F:	drivers/acpi/riscv/
+F:	include/linux/acpi_rimt.h
 
 ACPI PCC(Platform Communication Channel) MAILBOX DRIVER
 M:	Sudeep Holla <sudeep.holla@arm.com>
diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 36061f4732b7..96d64e0a7b97 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -16,6 +16,7 @@  config RISCV
 	select ACPI_MCFG if (ACPI && PCI)
 	select ACPI_PPTT if ACPI
 	select ACPI_REDUCED_HARDWARE_ONLY if ACPI
+        select ACPI_RIMT if ACPI
 	select ACPI_SPCR_TABLE if ACPI
 	select ARCH_DMA_DEFAULT_COHERENT
 	select ARCH_ENABLE_HUGEPAGE_MIGRATION if HUGETLB_PAGE && MIGRATION
diff --git a/drivers/acpi/Kconfig b/drivers/acpi/Kconfig
index 7bc40c2735ac..4381803c308c 100644
--- a/drivers/acpi/Kconfig
+++ b/drivers/acpi/Kconfig
@@ -546,6 +546,10 @@  if ARM64
 source "drivers/acpi/arm64/Kconfig"
 endif
 
+if RISCV
+source "drivers/acpi/riscv/Kconfig"
+endif
+
 config ACPI_PPTT
 	bool
 
diff --git a/drivers/acpi/riscv/Kconfig b/drivers/acpi/riscv/Kconfig
new file mode 100644
index 000000000000..046296a18d00
--- /dev/null
+++ b/drivers/acpi/riscv/Kconfig
@@ -0,0 +1,7 @@ 
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# ACPI Configuration for RISC-V
+#
+
+config ACPI_RIMT
+	bool
diff --git a/drivers/acpi/riscv/Makefile b/drivers/acpi/riscv/Makefile
index a96fdf1e2cb8..1284a076fa88 100644
--- a/drivers/acpi/riscv/Makefile
+++ b/drivers/acpi/riscv/Makefile
@@ -2,3 +2,4 @@ 
 obj-y					+= rhct.o init.o irq.o
 obj-$(CONFIG_ACPI_PROCESSOR_IDLE)	+= cpuidle.o
 obj-$(CONFIG_ACPI_CPPC_LIB)		+= cppc.o
+obj-$(CONFIG_ACPI_RIMT)			+= rimt.o
diff --git a/drivers/acpi/riscv/init.c b/drivers/acpi/riscv/init.c
index 673e4d5dd752..7c00f7995e86 100644
--- a/drivers/acpi/riscv/init.c
+++ b/drivers/acpi/riscv/init.c
@@ -10,4 +10,6 @@ 
 void __init acpi_arch_init(void)
 {
 	riscv_acpi_init_gsi_mapping();
+	if (IS_ENABLED(CONFIG_ACPI_RIMT))
+		riscv_acpi_rimt_init();
 }
diff --git a/drivers/acpi/riscv/init.h b/drivers/acpi/riscv/init.h
index 0b9a07e4031f..1680aa2aaf23 100644
--- a/drivers/acpi/riscv/init.h
+++ b/drivers/acpi/riscv/init.h
@@ -2,3 +2,4 @@ 
 #include <linux/init.h>
 
 void __init riscv_acpi_init_gsi_mapping(void);
+void __init riscv_acpi_rimt_init(void);
diff --git a/drivers/acpi/riscv/rimt.c b/drivers/acpi/riscv/rimt.c
new file mode 100644
index 000000000000..8cb6f5cf39e2
--- /dev/null
+++ b/drivers/acpi/riscv/rimt.c
@@ -0,0 +1,523 @@ 
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2024-2025, Ventana Micro Systems Inc
+ *	Author: Sunil V L <sunilvl@ventanamicro.com>
+ *
+ */
+
+#include <linux/acpi.h>
+#include <linux/acpi_rimt.h>
+#include <linux/iommu.h>
+#include <linux/list.h>
+#include <linux/pci.h>
+#include <linux/platform_device.h>
+#include "init.h"
+
+struct rimt_fwnode {
+	struct list_head list;
+	struct acpi_rimt_node *rimt_node;
+	struct fwnode_handle *fwnode;
+};
+
+static LIST_HEAD(rimt_fwnode_list);
+static DEFINE_SPINLOCK(rimt_fwnode_lock);
+
+#define RIMT_TYPE_MASK(type)	(1 << (type))
+#define RIMT_IOMMU_TYPE		BIT(0)
+
+/* Root pointer to the mapped RIMT table */
+static struct acpi_table_header *rimt_table;
+
+/**
+ * rimt_set_fwnode() - Create rimt_fwnode and use it to register
+ *		       iommu data in the rimt_fwnode_list
+ *
+ * @rimt_node: RIMT table node associated with the IOMMU
+ * @fwnode: fwnode associated with the RIMT node
+ *
+ * Returns: 0 on success
+ *          <0 on failure
+ */
+static inline int rimt_set_fwnode(struct acpi_rimt_node *rimt_node,
+				  struct fwnode_handle *fwnode)
+{
+	struct rimt_fwnode *np;
+
+	np = kzalloc(sizeof(*np), GFP_ATOMIC);
+
+	if (WARN_ON(!np))
+		return -ENOMEM;
+
+	INIT_LIST_HEAD(&np->list);
+	np->rimt_node = rimt_node;
+	np->fwnode = fwnode;
+
+	spin_lock(&rimt_fwnode_lock);
+	list_add_tail(&np->list, &rimt_fwnode_list);
+	spin_unlock(&rimt_fwnode_lock);
+
+	return 0;
+}
+
+/**
+ * rimt_get_fwnode() - Retrieve fwnode associated with an RIMT node
+ *
+ * @node: RIMT table node to be looked-up
+ *
+ * Returns: fwnode_handle pointer on success, NULL on failure
+ */
+static inline struct fwnode_handle *rimt_get_fwnode(struct acpi_rimt_node *node)
+{
+	struct rimt_fwnode *curr;
+	struct fwnode_handle *fwnode = NULL;
+
+	spin_lock(&rimt_fwnode_lock);
+	list_for_each_entry(curr, &rimt_fwnode_list, list) {
+		if (curr->rimt_node == node) {
+			fwnode = curr->fwnode;
+			break;
+		}
+	}
+	spin_unlock(&rimt_fwnode_lock);
+
+	return fwnode;
+}
+
+static acpi_status rimt_match_node_callback(struct acpi_rimt_node *node,
+					    void *context)
+{
+	struct device *dev = context;
+	acpi_status status = AE_NOT_FOUND;
+
+	if (node->type == ACPI_RIMT_NODE_TYPE_IOMMU) {
+		struct acpi_rimt_iommu *iommu_node = (struct acpi_rimt_iommu *)&node->node_data;
+
+		if (dev_is_pci(dev)) {
+			struct pci_dev *pdev;
+			u16 bdf;
+
+			pdev = to_pci_dev(dev);
+			bdf = PCI_DEVID(pdev->bus->number, pdev->devfn);
+			if ((pci_domain_nr(pdev->bus) == iommu_node->pcie_segment_number) &&
+			    bdf == iommu_node->pcie_bdf) {
+				status = AE_OK;
+			} else {
+				status = AE_NOT_FOUND;
+			}
+		} else {
+			struct platform_device *pdev = to_platform_device(dev);
+			struct resource *res;
+
+			res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+			if (res && res->start == iommu_node->base_address)
+				status = AE_OK;
+			else
+				status = AE_NOT_FOUND;
+		}
+	} else if (node->type == ACPI_RIMT_NODE_TYPE_PCIE_ROOT_COMPLEX) {
+		struct acpi_rimt_pcie_rc *pci_rc;
+		struct pci_bus *bus;
+
+		bus = to_pci_bus(dev);
+		pci_rc = (struct acpi_rimt_pcie_rc *)node->node_data;
+
+		/*
+		 * It is assumed that PCI segment numbers maps one-to-one
+		 * with root complexes. Each segment number can represent only
+		 * one root complex.
+		 */
+		status = pci_rc->pcie_segment_number == pci_domain_nr(bus) ?
+							AE_OK : AE_NOT_FOUND;
+	} else if (node->type == ACPI_RIMT_NODE_TYPE_PLAT_DEVICE) {
+		struct acpi_buffer buf = { ACPI_ALLOCATE_BUFFER, NULL };
+		struct acpi_device *adev;
+		struct acpi_rimt_platform_device *ncomp;
+		struct device *plat_dev = dev;
+
+		/*
+		 * Walk the device tree to find a device with an
+		 * ACPI companion; there is no point in scanning
+		 * RIMT for a device matching a platform device if
+		 * the device does not have an ACPI companion to
+		 * start with.
+		 */
+		do {
+			adev = ACPI_COMPANION(plat_dev);
+			if (adev)
+				break;
+
+			plat_dev = plat_dev->parent;
+		} while (plat_dev);
+
+		if (!adev)
+			return status;
+
+		status = acpi_get_name(adev->handle, ACPI_FULL_PATHNAME, &buf);
+		if (ACPI_FAILURE(status)) {
+			dev_warn(plat_dev, "Can't get device full path name\n");
+			return status;
+		}
+
+		ncomp = (struct acpi_rimt_platform_device *)node->node_data;
+		status = !strcmp(ncomp->device_name, buf.pointer) ?
+							AE_OK : AE_NOT_FOUND;
+		acpi_os_free(buf.pointer);
+	}
+
+	return status;
+}
+
+static struct acpi_rimt_node *rimt_scan_node(enum acpi_rimt_node_type type,
+					     void *context)
+{
+	struct acpi_rimt_node *rimt_node, *rimt_end;
+	struct acpi_table_rimt *rimt;
+	int i;
+
+	if (!rimt_table)
+		return NULL;
+
+	/* Get the first RIMT node */
+	rimt = (struct acpi_table_rimt *)rimt_table;
+	rimt_node = ACPI_ADD_PTR(struct acpi_rimt_node, rimt,
+				 rimt->node_offset);
+	rimt_end = ACPI_ADD_PTR(struct acpi_rimt_node, rimt_table,
+				rimt_table->length);
+
+	for (i = 0; i < rimt->num_nodes; i++) {
+		if (WARN_TAINT(rimt_node >= rimt_end, TAINT_FIRMWARE_WORKAROUND,
+			       "RIMT node pointer overflows, bad table!\n"))
+			return NULL;
+
+		if (rimt_node->type == type &&
+		    ACPI_SUCCESS(rimt_match_node_callback(rimt_node, context)))
+			return rimt_node;
+
+		rimt_node = ACPI_ADD_PTR(struct acpi_rimt_node, rimt_node,
+					 rimt_node->length);
+	}
+
+	return NULL;
+}
+
+static bool rimt_pcie_rc_supports_ats(struct acpi_rimt_node *node)
+{
+	struct acpi_rimt_pcie_rc *pci_rc;
+
+	pci_rc = (struct acpi_rimt_pcie_rc *)node->node_data;
+	return pci_rc->flags & ACPI_RIMT_PCIE_ATS_SUPPORTED;
+}
+
+static int rimt_iommu_xlate(struct device *dev, struct acpi_rimt_node *node, u32 deviceid)
+{
+	struct fwnode_handle *rimt_fwnode;
+
+	if (!node)
+		return -ENODEV;
+
+	rimt_fwnode = rimt_get_fwnode(node);
+
+	/*
+	 * The IOMMU drivers may not be probed yet.
+	 * Defer the IOMMU configuration
+	 */
+	if (!rimt_fwnode)
+		return -EPROBE_DEFER;
+
+	return acpi_iommu_fwspec_init(dev, deviceid, rimt_fwnode);
+}
+
+struct rimt_pci_alias_info {
+	struct device *dev;
+	struct acpi_rimt_node *node;
+	const struct iommu_ops *ops;
+};
+
+static int rimt_id_map(struct acpi_rimt_id_mapping *map, u8 type, u32 rid_in, u32 *rid_out)
+{
+	if (rid_in < map->source_id_base ||
+	    (rid_in > map->source_id_base + map->num_ids))
+		return -ENXIO;
+
+	*rid_out = map->dest_id_base + (rid_in - map->source_id_base);
+	return 0;
+}
+
+static struct acpi_rimt_node *rimt_node_get_id(struct acpi_rimt_node *node,
+					       u32 *id_out, int index)
+{
+	struct acpi_rimt_platform_device *plat_node;
+	struct acpi_rimt_pcie_rc *pci_node;
+	u32 id_mapping_offset, num_id_mapping;
+	struct acpi_rimt_id_mapping *map;
+	struct acpi_rimt_node *parent;
+
+	if (node->type == ACPI_RIMT_NODE_TYPE_PCIE_ROOT_COMPLEX) {
+		pci_node = (struct acpi_rimt_pcie_rc *)&node->node_data;
+		id_mapping_offset = pci_node->id_mapping_offset;
+		num_id_mapping = pci_node->num_id_mappings;
+	} else if (node->type == ACPI_RIMT_NODE_TYPE_PLAT_DEVICE) {
+		plat_node = (struct acpi_rimt_platform_device *)&node->node_data;
+		id_mapping_offset = plat_node->id_mapping_offset;
+		num_id_mapping = plat_node->num_id_mappings;
+	} else {
+		return NULL;
+	}
+
+	if (!id_mapping_offset || !num_id_mapping || index >= num_id_mapping)
+		return NULL;
+
+	map = ACPI_ADD_PTR(struct acpi_rimt_id_mapping, node,
+			   id_mapping_offset + index * sizeof(*map));
+
+	/* Firmware bug! */
+	if (!map->dest_offset) {
+		pr_err(FW_BUG "[node %p type %d] ID map has NULL parent reference\n",
+		       node, node->type);
+		return NULL;
+	}
+
+	parent = ACPI_ADD_PTR(struct acpi_rimt_node, rimt_table, map->dest_offset);
+
+	if (node->type == ACPI_RIMT_NODE_TYPE_PLAT_DEVICE ||
+	    node->type == ACPI_RIMT_NODE_TYPE_PCIE_ROOT_COMPLEX) {
+		*id_out = map->dest_offset;
+		return parent;
+	}
+
+	return NULL;
+}
+
+static struct acpi_rimt_node *rimt_node_map_id(struct acpi_rimt_node *node,
+					       u32 id_in, u32 *id_out,
+					       u8 type_mask)
+{
+	struct acpi_rimt_pcie_rc *pci_node;
+	struct acpi_rimt_platform_device *plat_node;
+	u32 id = id_in;
+	u32 id_mapping_offset, num_id_mapping;
+
+	/* Parse the ID mapping tree to find specified node type */
+	while (node) {
+		struct acpi_rimt_id_mapping *map;
+		int i, rc = 0;
+		u32 map_id = id;
+
+		if (RIMT_TYPE_MASK(node->type) & type_mask) {
+			if (id_out)
+				*id_out = id;
+			return node;
+		}
+
+		if (node->type == ACPI_RIMT_NODE_TYPE_PCIE_ROOT_COMPLEX) {
+			pci_node = (struct acpi_rimt_pcie_rc *)&node->node_data;
+			id_mapping_offset = pci_node->id_mapping_offset;
+			num_id_mapping = pci_node->num_id_mappings;
+		} else if (node->type == ACPI_RIMT_NODE_TYPE_PLAT_DEVICE) {
+			plat_node = (struct acpi_rimt_platform_device *)&node->node_data;
+			id_mapping_offset = plat_node->id_mapping_offset;
+			num_id_mapping = plat_node->num_id_mappings;
+		} else {
+			goto fail_map;
+		}
+
+		if (!id_mapping_offset || !num_id_mapping)
+			goto fail_map;
+
+		map = ACPI_ADD_PTR(struct acpi_rimt_id_mapping, node,
+				   id_mapping_offset);
+
+		/* Firmware bug! */
+		if (!map->dest_offset) {
+			pr_err(FW_BUG "[node %p type %d] ID map has NULL parent reference\n",
+			       node, node->type);
+			goto fail_map;
+		}
+
+		/* Do the ID translation */
+		for (i = 0; i < num_id_mapping; i++, map++) {
+			rc = rimt_id_map(map, node->type, map_id, &id);
+			if (!rc)
+				break;
+		}
+
+		if (i == num_id_mapping)
+			goto fail_map;
+
+		node = ACPI_ADD_PTR(struct acpi_rimt_node, rimt_table,
+				    rc ? 0 : map->dest_offset);
+	}
+
+fail_map:
+	/* Map input ID to output ID unchanged on mapping failure */
+	if (id_out)
+		*id_out = id_in;
+
+	return NULL;
+}
+
+static struct acpi_rimt_node *rimt_node_map_platform_id(struct acpi_rimt_node *node, u32 *id_out,
+							u8 type_mask, int index)
+{
+	struct acpi_rimt_node *parent;
+	u32 id;
+
+	parent = rimt_node_get_id(node, &id, index);
+	if (!parent)
+		return NULL;
+
+	if (!(RIMT_TYPE_MASK(parent->type) & type_mask))
+		parent = rimt_node_map_id(parent, id, id_out, type_mask);
+	else
+		if (id_out)
+			*id_out = id;
+
+	return parent;
+}
+
+static int rimt_pci_iommu_init(struct pci_dev *pdev, u16 alias, void *data)
+{
+	struct rimt_pci_alias_info *info = data;
+	struct acpi_rimt_node *parent;
+	u32 deviceid;
+
+	parent = rimt_node_map_id(info->node, alias, &deviceid, RIMT_IOMMU_TYPE);
+	return rimt_iommu_xlate(info->dev, parent, deviceid);
+}
+
+/*
+ * RISC-V supports IOMMU as a PCI device or a platform device.
+ * When it is a platform device, there should be a namespace device as
+ * well along with RIMT. To create the link between RIMT information and
+ * the platform device, the IOMMU driver should register itself with the
+ * RIMT module. This is true for PCI based IOMMU as well.
+ */
+int rimt_iommu_register(struct device *dev)
+{
+	struct fwnode_handle *rimt_fwnode;
+	struct acpi_rimt_node *node;
+
+	node = rimt_scan_node(ACPI_RIMT_NODE_TYPE_IOMMU, dev);
+	if (!node) {
+		pr_err("Could not find IOMMU node in RIMT\n");
+		return -ENODEV;
+	}
+
+	if (dev_is_pci(dev)) {
+		rimt_fwnode = acpi_alloc_fwnode_static();
+		if (!rimt_fwnode)
+			return -ENOMEM;
+
+		rimt_fwnode->dev = dev;
+		if (!dev->fwnode)
+			dev->fwnode = rimt_fwnode;
+
+		rimt_set_fwnode(node, rimt_fwnode);
+	} else {
+		rimt_set_fwnode(node, dev->fwnode);
+	}
+
+	return 0;
+}
+
+#ifdef CONFIG_IOMMU_API
+
+static int rimt_plat_iommu_map(struct device *dev, struct acpi_rimt_node *node)
+{
+	struct acpi_rimt_node *parent;
+	int err = -ENODEV, i = 0;
+	u32 deviceid = 0;
+
+	do {
+		parent = rimt_node_map_platform_id(node, &deviceid,
+						   RIMT_IOMMU_TYPE,
+						   i++);
+
+		if (parent)
+			err = rimt_iommu_xlate(dev, parent, deviceid);
+	} while (parent && !err);
+
+	return err;
+}
+
+static int rimt_plat_iommu_map_id(struct device *dev,
+				  struct acpi_rimt_node *node,
+				  const u32 *in_id)
+{
+	struct acpi_rimt_node *parent;
+	u32 deviceid;
+
+	parent = rimt_node_map_id(node, *in_id, &deviceid, RIMT_IOMMU_TYPE);
+	if (parent)
+		return rimt_iommu_xlate(dev, parent, deviceid);
+
+	return -ENODEV;
+}
+
+/**
+ * rimt_iommu_configure_id - Set-up IOMMU configuration for a device.
+ *
+ * @dev: device to configure
+ * @id_in: optional input id const value pointer
+ *
+ * Returns: 0 on success, <0 on failure
+ */
+int rimt_iommu_configure_id(struct device *dev, const u32 *id_in)
+{
+	struct acpi_rimt_node *node;
+	int err = -ENODEV;
+
+	if (dev_is_pci(dev)) {
+		struct iommu_fwspec *fwspec;
+		struct pci_bus *bus = to_pci_dev(dev)->bus;
+		struct rimt_pci_alias_info info = { .dev = dev };
+
+		node = rimt_scan_node(ACPI_RIMT_NODE_TYPE_PCIE_ROOT_COMPLEX, &bus->dev);
+		if (!node)
+			return -ENODEV;
+
+		info.node = node;
+		err = pci_for_each_dma_alias(to_pci_dev(dev),
+					     rimt_pci_iommu_init, &info);
+
+		fwspec = dev_iommu_fwspec_get(dev);
+		if (fwspec && rimt_pcie_rc_supports_ats(node))
+			fwspec->flags |= IOMMU_FWSPEC_PCI_RC_ATS;
+	} else {
+		node = rimt_scan_node(ACPI_RIMT_NODE_TYPE_PLAT_DEVICE, dev);
+		if (!node)
+			return -ENODEV;
+
+		err = id_in ? rimt_plat_iommu_map_id(dev, node, id_in) :
+			      rimt_plat_iommu_map(dev, node);
+	}
+
+	return err;
+}
+
+#else
+int rimt_iommu_configure_id(struct device *dev, const u32 *id_in)
+{
+	return -ENODEV;
+}
+#endif
+
+void __init riscv_acpi_rimt_init(void)
+{
+	acpi_status status;
+
+	/* rimt_table will be used at runtime after the rimt init,
+	 * so we don't need to call acpi_put_table() to release
+	 * the RIMT table mapping.
+	 */
+	status = acpi_get_table(ACPI_SIG_RIMT, 0, &rimt_table);
+	if (ACPI_FAILURE(status)) {
+		if (status != AE_NOT_FOUND) {
+			const char *msg = acpi_format_exception(status);
+
+			pr_err("Failed to get table, %s\n", msg);
+		}
+
+		return;
+	}
+}
diff --git a/include/linux/acpi_rimt.h b/include/linux/acpi_rimt.h
new file mode 100644
index 000000000000..ce4d136d4f81
--- /dev/null
+++ b/include/linux/acpi_rimt.h
@@ -0,0 +1,26 @@ 
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ *  Copyright (C) 2024-2025, Ventana Micro Systems Inc.
+ *	Author: Sunil V L <sunilvl@ventanamicro.com>
+ */
+
+#ifndef _ACPI_RIMT_H
+#define _ACPI_RIMT_H
+
+#ifdef CONFIG_ACPI_RIMT
+int rimt_iommu_configure_id(struct device *dev, const u32 *id_in);
+
+int rimt_iommu_register(struct device *dev);
+#else
+static inline int rimt_iommu_register(struct device *dev)
+{
+	return -ENODEV;
+}
+
+static inline int rimt_iommu_configure_id(struct device *dev, const u32 *id_in)
+{
+	return -ENODEV;
+}
+#endif
+
+#endif /* _ACPI_RIMT_H */