[RFC PATCH v2 04/18] iommu/riscv: Add IRQ domain for interrupt remapping

[Andrew Jones <ajones@ventanamicro.com>]

This is just a skeleton. Until irq-set-affinity functions are
implemented the IRQ domain doesn't serve any purpose.

Signed-off-by: Andrew Jones <ajones@ventanamicro.com>
---
 drivers/iommu/riscv/Makefile   |   2 +-
 drivers/iommu/riscv/iommu-ir.c | 114 +++++++++++++++++++++++++++++++++
 drivers/iommu/riscv/iommu.c    |  36 +++++++++++
 drivers/iommu/riscv/iommu.h    |  12 ++++
 4 files changed, 163 insertions(+), 1 deletion(-)
 create mode 100644 drivers/iommu/riscv/iommu-ir.c

diff --git a/drivers/iommu/riscv/Makefile b/drivers/iommu/riscv/Makefile
index b5929f9f23e6..9c83f877d50f 100644
--- a/drivers/iommu/riscv/Makefile
+++ b/drivers/iommu/riscv/Makefile
@@ -1,3 +1,3 @@
 # SPDX-License-Identifier: GPL-2.0-only
-obj-y += iommu.o iommu-platform.o
+obj-y += iommu.o iommu-ir.o iommu-platform.o
 obj-$(CONFIG_RISCV_IOMMU_PCI) += iommu-pci.o
diff --git a/drivers/iommu/riscv/iommu-ir.c b/drivers/iommu/riscv/iommu-ir.c
new file mode 100644
index 000000000000..08cf159b587d
--- /dev/null
+++ b/drivers/iommu/riscv/iommu-ir.c
@@ -0,0 +1,114 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * IOMMU Interrupt Remapping
+ *
+ * Copyright © 2025 Ventana Micro Systems Inc.
+ */
+#include <linux/irqdomain.h>
+#include <linux/msi.h>
+
+#include "iommu.h"
+
+static struct irq_chip riscv_iommu_ir_irq_chip = {
+	.name			= "IOMMU-IR",
+	.irq_ack		= irq_chip_ack_parent,
+	.irq_mask		= irq_chip_mask_parent,
+	.irq_unmask		= irq_chip_unmask_parent,
+	.irq_set_affinity	= irq_chip_set_affinity_parent,
+};
+
+static int riscv_iommu_ir_irq_domain_alloc_irqs(struct irq_domain *irqdomain,
+						unsigned int irq_base, unsigned int nr_irqs,
+						void *arg)
+{
+	struct irq_data *data;
+	int i, ret;
+
+	ret = irq_domain_alloc_irqs_parent(irqdomain, irq_base, nr_irqs, arg);
+	if (ret)
+		return ret;
+
+	for (i = 0; i < nr_irqs; i++) {
+		data = irq_domain_get_irq_data(irqdomain, irq_base + i);
+		data->chip = &riscv_iommu_ir_irq_chip;
+	}
+
+	return 0;
+}
+
+static const struct irq_domain_ops riscv_iommu_ir_irq_domain_ops = {
+	.alloc = riscv_iommu_ir_irq_domain_alloc_irqs,
+	.free = irq_domain_free_irqs_parent,
+};
+
+static const struct msi_parent_ops riscv_iommu_ir_msi_parent_ops = {
+	.prefix			= "IR-",
+	.supported_flags	= MSI_GENERIC_FLAGS_MASK |
+				  MSI_FLAG_PCI_MSIX,
+	.required_flags		= MSI_FLAG_USE_DEF_DOM_OPS |
+				  MSI_FLAG_USE_DEF_CHIP_OPS |
+				  MSI_FLAG_PCI_MSI_MASK_PARENT,
+	.chip_flags		= MSI_CHIP_FLAG_SET_ACK,
+	.init_dev_msi_info	= msi_parent_init_dev_msi_info,
+};
+
+struct irq_domain *riscv_iommu_ir_irq_domain_create(struct riscv_iommu_device *iommu,
+						    struct device *dev,
+						    struct riscv_iommu_info *info)
+{
+	struct irq_domain *irqparent = dev_get_msi_domain(dev);
+	struct irq_domain *irqdomain;
+	struct fwnode_handle *fn;
+	char *fwname;
+
+	fwname = kasprintf(GFP_KERNEL, "IOMMU-IR-%s", dev_name(dev));
+	if (!fwname)
+		return NULL;
+
+	fn = irq_domain_alloc_named_fwnode(fwname);
+	kfree(fwname);
+	if (!fn) {
+		dev_err(iommu->dev, "Couldn't allocate fwnode\n");
+		return NULL;
+	}
+
+	irqdomain = irq_domain_create_hierarchy(irqparent, 0, 0, fn,
+						&riscv_iommu_ir_irq_domain_ops,
+						info);
+	if (!irqdomain) {
+		dev_err(iommu->dev, "Failed to create IOMMU irq domain\n");
+		irq_domain_free_fwnode(fn);
+		return NULL;
+	}
+
+	irqdomain->flags |= IRQ_DOMAIN_FLAG_MSI_PARENT;
+	irqdomain->msi_parent_ops = &riscv_iommu_ir_msi_parent_ops;
+	irq_domain_update_bus_token(irqdomain, DOMAIN_BUS_MSI_REMAP);
+
+	dev_set_msi_domain(dev, irqdomain);
+
+	return irqdomain;
+}
+
+void riscv_iommu_ir_irq_domain_remove(struct riscv_iommu_info *info)
+{
+	struct fwnode_handle *fn;
+
+	if (!info->irqdomain)
+		return;
+
+	fn = info->irqdomain->fwnode;
+	irq_domain_remove(info->irqdomain);
+	info->irqdomain = NULL;
+	irq_domain_free_fwnode(fn);
+}
+
+int riscv_iommu_ir_attach_paging_domain(struct riscv_iommu_domain *domain,
+					struct device *dev)
+{
+	return 0;
+}
+
+void riscv_iommu_ir_free_paging_domain(struct riscv_iommu_domain *domain)
+{
+}
diff --git a/drivers/iommu/riscv/iommu.c b/drivers/iommu/riscv/iommu.c
index a44c67a848fa..db2acd9dc64b 100644
--- a/drivers/iommu/riscv/iommu.c
+++ b/drivers/iommu/riscv/iommu.c
@@ -17,6 +17,8 @@
 #include <linux/init.h>
 #include <linux/iommu.h>
 #include <linux/iopoll.h>
+#include <linux/irqchip/riscv-imsic.h>
+#include <linux/irqdomain.h>
 #include <linux/kernel.h>
 #include <linux/pci.h>
 
@@ -1026,6 +1028,9 @@ static void riscv_iommu_iodir_update(struct riscv_iommu_device *iommu,
 
 		WRITE_ONCE(dc->fsc, new_dc->fsc);
 		WRITE_ONCE(dc->ta, new_dc->ta & RISCV_IOMMU_PC_TA_PSCID);
+		WRITE_ONCE(dc->msiptp, new_dc->msiptp);
+		WRITE_ONCE(dc->msi_addr_mask, new_dc->msi_addr_mask);
+		WRITE_ONCE(dc->msi_addr_pattern, new_dc->msi_addr_pattern);
 		/* Update device context, write TC.V as the last step. */
 		dma_wmb();
 		WRITE_ONCE(dc->tc, tc);
@@ -1276,6 +1281,8 @@ static void riscv_iommu_free_paging_domain(struct iommu_domain *iommu_domain)
 
 	WARN_ON(!list_empty(&domain->bonds));
 
+	riscv_iommu_ir_free_paging_domain(domain);
+
 	if ((int)domain->pscid > 0)
 		ida_free(&riscv_iommu_pscids, domain->pscid);
 
@@ -1305,15 +1312,28 @@ static int riscv_iommu_attach_paging_domain(struct iommu_domain *iommu_domain,
 	struct riscv_iommu_device *iommu = dev_to_iommu(dev);
 	struct riscv_iommu_info *info = dev_iommu_priv_get(dev);
 	struct riscv_iommu_dc dc = {0};
+	int ret;
 
 	if (!riscv_iommu_pt_supported(iommu, domain->pgd_mode))
 		return -ENODEV;
 
+	ret = riscv_iommu_ir_attach_paging_domain(domain, dev);
+	if (ret)
+		return ret;
+
 	dc.fsc = FIELD_PREP(RISCV_IOMMU_PC_FSC_MODE, domain->pgd_mode) |
 		 FIELD_PREP(RISCV_IOMMU_PC_FSC_PPN, virt_to_pfn(domain->pgd_root));
 	dc.ta = FIELD_PREP(RISCV_IOMMU_PC_TA_PSCID, domain->pscid) |
 			   RISCV_IOMMU_PC_TA_V;
 
+	if (domain->msi_root) {
+		dc.msiptp = virt_to_pfn(domain->msi_root) |
+			    FIELD_PREP(RISCV_IOMMU_DC_MSIPTP_MODE,
+				       RISCV_IOMMU_DC_MSIPTP_MODE_FLAT);
+		dc.msi_addr_mask = domain->msi_addr_mask;
+		dc.msi_addr_pattern = domain->msi_addr_pattern;
+	}
+
 	if (riscv_iommu_bond_link(domain, dev))
 		return -ENOMEM;
 
@@ -1466,6 +1486,8 @@ static int riscv_iommu_of_xlate(struct device *dev, const struct of_phandle_args
 static struct iommu_device *riscv_iommu_probe_device(struct device *dev)
 {
 	struct iommu_fwspec *fwspec = dev_iommu_fwspec_get(dev);
+	const struct imsic_global_config *imsic_global;
+	struct irq_domain *irqdomain = NULL;
 	struct riscv_iommu_device *iommu;
 	struct riscv_iommu_info *info;
 	struct riscv_iommu_dc *dc;
@@ -1489,6 +1511,18 @@ static struct iommu_device *riscv_iommu_probe_device(struct device *dev)
 	info = kzalloc(sizeof(*info), GFP_KERNEL);
 	if (!info)
 		return ERR_PTR(-ENOMEM);
+
+	imsic_global = imsic_get_global_config();
+	if (imsic_global && imsic_global->nr_ids) {
+		irqdomain = riscv_iommu_ir_irq_domain_create(iommu, dev, info);
+		if (!irqdomain) {
+			kfree(info);
+			return ERR_PTR(-ENOMEM);
+		}
+	}
+
+	info->irqdomain = irqdomain;
+
 	/*
 	 * Allocate and pre-configure device context entries in
 	 * the device directory. Do not mark the context valid yet.
@@ -1499,6 +1533,7 @@ static struct iommu_device *riscv_iommu_probe_device(struct device *dev)
 	for (i = 0; i < fwspec->num_ids; i++) {
 		dc = riscv_iommu_get_dc(iommu, fwspec->ids[i]);
 		if (!dc) {
+			riscv_iommu_ir_irq_domain_remove(info);
 			kfree(info);
 			return ERR_PTR(-ENODEV);
 		}
@@ -1516,6 +1551,7 @@ static void riscv_iommu_release_device(struct device *dev)
 {
 	struct riscv_iommu_info *info = dev_iommu_priv_get(dev);
 
+	riscv_iommu_ir_irq_domain_remove(info);
 	kfree_rcu_mightsleep(info);
 }
 
diff --git a/drivers/iommu/riscv/iommu.h b/drivers/iommu/riscv/iommu.h
index 1d163cbd9e4d..640d825f11b9 100644
--- a/drivers/iommu/riscv/iommu.h
+++ b/drivers/iommu/riscv/iommu.h
@@ -27,11 +27,15 @@ struct riscv_iommu_domain {
 	int numa_node;
 	unsigned int pgd_mode;
 	unsigned long *pgd_root;
+	struct riscv_iommu_msipte *msi_root;
+	u64 msi_addr_mask;
+	u64 msi_addr_pattern;
 };
 
 /* Private IOMMU data for managed devices, dev_iommu_priv_* */
 struct riscv_iommu_info {
 	struct riscv_iommu_domain *domain;
+	struct irq_domain *irqdomain;
 };
 
 struct riscv_iommu_device;
@@ -86,6 +90,14 @@ int riscv_iommu_init(struct riscv_iommu_device *iommu);
 void riscv_iommu_remove(struct riscv_iommu_device *iommu);
 void riscv_iommu_disable(struct riscv_iommu_device *iommu);
 
+struct irq_domain *riscv_iommu_ir_irq_domain_create(struct riscv_iommu_device *iommu,
+						    struct device *dev,
+						    struct riscv_iommu_info *info);
+void riscv_iommu_ir_irq_domain_remove(struct riscv_iommu_info *info);
+int riscv_iommu_ir_attach_paging_domain(struct riscv_iommu_domain *domain,
+					struct device *dev);
+void riscv_iommu_ir_free_paging_domain(struct riscv_iommu_domain *domain);
+
 #define riscv_iommu_readl(iommu, addr) \
 	readl_relaxed((iommu)->reg + (addr))
 
-- 
2.49.0