irqchip/gic-v5: Add GICv5 ITS support

The GICv5 architecture implements Interrupt Translation Service
(ITS) components in order to translate events coming from peripherals
into interrupt events delivered to the connected IRSes.

Events (ie MSI memory writes to ITS translate frame), are translated
by the ITS using tables kept in memory.

ITS translation tables for peripherals is kept in memory storage
(device table [DT] and Interrupt Translation Table [ITT]) that
is allocated by the driver on boot.

Both tables can be 1- or 2-level; the structure is chosen by the
driver after probing the ITS HW parameters and checking the
allowed table splits and supported {device/event}_IDbits.

DT table entries are allocated on demand (ie when a device is
probed); the DT table is sized using the number of supported
deviceID bits in that that's a system design decision (ie the
number of deviceID bits implemented should reflect the number
of devices expected in a system) therefore it makes sense to
allocate a DT table that can cater for the maximum number of
devices.

DT and ITT tables are allocated using the kmalloc interface;
the allocation size may be smaller than a page or larger,
and must provide contiguous memory pages.

LPIs INTIDs backing the device events are allocated one-by-one
and only upon Linux IRQ allocation; this to avoid preallocating
a large number of LPIs to cover the HW device MSI vector
size whereas few MSI entries are actually enabled by a device.

ITS cacheability/shareability attributes are programmed
according to the provided firmware ITS description.

The GICv5 partially reuses the GICv3 ITS MSI parent infrastructure
and adds functions required to retrieve the ITS translate frame
addresses out of msi-map and msi-parent properties to implement
the GICv5 ITS MSI parent callbacks.

Co-developed-by: Sascha Bischoff <[e-mail]>
Signed-off-by: Sascha Bischoff <[e-mail]>
Co-developed-by: Timothy Hayes <[e-mail]>
Signed-off-by: Timothy Hayes <[e-mail]>
Signed-off-by: Lorenzo Pieralisi <[e-mail]>
Reviewed-by: Marc Zyngier <[e-mail]>
Cc: Thomas Gleixner <[e-mail]>
Cc: Marc Zyngier <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Marc Zyngier <[e-mail]>

MAINTAINERS

···
 L:	[e-mail] (moderated for non-subscribers)
 S:	Maintained
 F:	Documentation/devicetree/bindings/interrupt-controller/arm,gic-v5*.yaml
+F:	drivers/irqchip/irq-gic-its-msi-parent.[ch]
 F:	drivers/irqchip/irq-gic-v5*.[ch]
 F:	include/linux/irqchip/arm-gic-v5.h
 

drivers/irqchip/Kconfig

···
 	bool
 	select IRQ_DOMAIN_HIERARCHY
 	select GENERIC_IRQ_EFFECTIVE_AFF_MASK
+	select GENERIC_MSI_IRQ
+	select IRQ_MSI_LIB
+	select ARM_GIC_ITS_PARENT
 
 config ARM_NVIC
 	bool

drivers/irqchip/Makefile

···
 obj-$(CONFIG_ARM_GIC_V3_ITS)		+= irq-gic-v3-its.o irq-gic-v4.o
 obj-$(CONFIG_ARM_GIC_V3_ITS_FSL_MC)	+= irq-gic-v3-its-fsl-mc-msi.o
 obj-$(CONFIG_PARTITION_PERCPU)		+= irq-partition-percpu.o
-obj-$(CONFIG_ARM_GIC_V5)		+= irq-gic-v5.o irq-gic-v5-irs.o
+obj-$(CONFIG_ARM_GIC_V5)		+= irq-gic-v5.o irq-gic-v5-irs.o irq-gic-v5-its.o
 obj-$(CONFIG_HISILICON_IRQ_MBIGEN)	+= irq-mbigen.o
 obj-$(CONFIG_ARM_NVIC)			+= irq-nvic.o
 obj-$(CONFIG_ARM_VIC)			+= irq-vic.o

drivers/irqchip/irq-gic-its-msi-parent.c

···
 // Copyright (C) 2022 Intel
 
 #include <linux/acpi_iort.h>
+#include <linux/of_address.h>
 #include <linux/pci.h>
 
 #include "irq-gic-its-msi-parent.h"
···
 #define ITS_MSI_FLAGS_SUPPORTED (MSI_GENERIC_FLAGS_MASK |	\
 				 MSI_FLAG_PCI_MSIX      |	\
 				 MSI_FLAG_MULTI_PCI_MSI)
+
+static int its_translate_frame_address(struct device_node *msi_node, phys_addr_t *pa)
+{
+	struct resource res;
+	int ret;
+
+	ret = of_property_match_string(msi_node, "reg-names", "ns-translate");
+	if (ret < 0)
+		return ret;
+
+	ret = of_address_to_resource(msi_node, ret, &res);
+	if (ret)
+		return ret;
+
+	*pa = res.start;
+	return 0;
+}
 
 #ifdef CONFIG_PCI_MSI
 static int its_pci_msi_vec_count(struct pci_dev *pdev, void *data)
···
 	msi_info = msi_get_domain_info(domain->parent);
 	return msi_info->ops->msi_prepare(domain->parent, dev, nvec, info);
 }
+
+static int its_v5_pci_msi_prepare(struct irq_domain *domain, struct device *dev,
+				  int nvec, msi_alloc_info_t *info)
+{
+	struct device_node *msi_node = NULL;
+	struct msi_domain_info *msi_info;
+	struct pci_dev *pdev;
+	phys_addr_t pa;
+	u32 rid;
+	int ret;
+
+	if (!dev_is_pci(dev))
+		return -EINVAL;
+
+	pdev = to_pci_dev(dev);
+
+	rid = pci_msi_map_rid_ctlr_node(pdev, &msi_node);
+	if (!msi_node)
+		return -ENODEV;
+
+	ret = its_translate_frame_address(msi_node, &pa);
+	if (ret)
+		return -ENODEV;
+
+	of_node_put(msi_node);
+
+	/* ITS specific DeviceID */
+	info->scratchpad[0].ul = rid;
+	/* ITS translate frame physical address */
+	info->scratchpad[1].ul = pa;
+
+	/* Always allocate power of two vectors */
+	nvec = roundup_pow_of_two(nvec);
+
+	msi_info = msi_get_domain_info(domain->parent);
+	return msi_info->ops->msi_prepare(domain->parent, dev, nvec, info);
+}
 #else /* CONFIG_PCI_MSI */
 #define its_pci_msi_prepare	NULL
+#define its_v5_pci_msi_prepare	NULL
 #endif /* !CONFIG_PCI_MSI */
 
 static int of_pmsi_get_dev_id(struct irq_domain *domain, struct device *dev,
···
 	return ret;
 }
 
+static int of_v5_pmsi_get_msi_info(struct irq_domain *domain, struct device *dev,
+				   u32 *dev_id, phys_addr_t *pa)
+{
+	int ret, index = 0;
+	/*
+	 * Retrieve the DeviceID and the ITS translate frame node pointer
+	 * out of the msi-parent property.
+	 */
+	do {
+		struct of_phandle_args args;
+
+		ret = of_parse_phandle_with_args(dev->of_node,
+						 "msi-parent", "#msi-cells",
+						 index, &args);
+		if (ret)
+			break;
+		/*
+		 * The IRQ domain fwnode is the msi controller parent
+		 * in GICv5 (where the msi controller nodes are the
+		 * ITS translate frames).
+		 */
+		if (args.np->parent == irq_domain_get_of_node(domain)) {
+			if (WARN_ON(args.args_count != 1))
+				return -EINVAL;
+			*dev_id = args.args[0];
+
+			ret = its_translate_frame_address(args.np, pa);
+			if (ret)
+				return -ENODEV;
+			break;
+		}
+		index++;
+	} while (!ret);
+
+	if (ret) {
+		struct device_node *np = NULL;
+
+		ret = of_map_id(dev->of_node, dev->id, "msi-map", "msi-map-mask", &np, dev_id);
+		if (np) {
+			ret = its_translate_frame_address(np, pa);
+			of_node_put(np);
+		}
+	}
+
+	return ret;
+}
+
 int __weak iort_pmsi_get_dev_id(struct device *dev, u32 *dev_id)
 {
 	return -1;
···
 	msi_info = msi_get_domain_info(domain->parent);
 	return msi_info->ops->msi_prepare(domain->parent,
 					  dev, nvec, info);
+}
+
+static int its_v5_pmsi_prepare(struct irq_domain *domain, struct device *dev,
+			       int nvec, msi_alloc_info_t *info)
+{
+	struct msi_domain_info *msi_info;
+	phys_addr_t pa;
+	u32 dev_id;
+	int ret;
+
+	if (!dev->of_node)
+		return -ENODEV;
+
+	ret = of_v5_pmsi_get_msi_info(domain->parent, dev, &dev_id, &pa);
+	if (ret)
+		return ret;
+
+	/* ITS specific DeviceID */
+	info->scratchpad[0].ul = dev_id;
+	/* ITS translate frame physical address */
+	info->scratchpad[1].ul = pa;
+
+	/* Allocate always as a power of 2 */
+	nvec = roundup_pow_of_two(nvec);
+
+	msi_info = msi_get_domain_info(domain->parent);
+	return msi_info->ops->msi_prepare(domain->parent, dev, nvec, info);
 }
 
 static void its_msi_teardown(struct irq_domain *domain, msi_alloc_info_t *info)
···
 	return true;
 }
 
+static bool its_v5_init_dev_msi_info(struct device *dev, struct irq_domain *domain,
+				     struct irq_domain *real_parent, struct msi_domain_info *info)
+{
+	if (!msi_lib_init_dev_msi_info(dev, domain, real_parent, info))
+		return false;
+
+	switch (info->bus_token) {
+	case DOMAIN_BUS_PCI_DEVICE_MSI:
+	case DOMAIN_BUS_PCI_DEVICE_MSIX:
+		info->ops->msi_prepare = its_v5_pci_msi_prepare;
+		info->ops->msi_teardown = its_msi_teardown;
+		break;
+	case DOMAIN_BUS_DEVICE_MSI:
+	case DOMAIN_BUS_WIRED_TO_MSI:
+		info->ops->msi_prepare = its_v5_pmsi_prepare;
+		info->ops->msi_teardown = its_msi_teardown;
+		break;
+	default:
+		/* Confused. How did the lib return true? */
+		WARN_ON_ONCE(1);
+		return false;
+	}
+
+	return true;
+}
+
 const struct msi_parent_ops gic_v3_its_msi_parent_ops = {
 	.supported_flags	= ITS_MSI_FLAGS_SUPPORTED,
 	.required_flags		= ITS_MSI_FLAGS_REQUIRED,
···
 	.bus_select_mask	= MATCH_PCI_MSI | MATCH_PLATFORM_MSI,
 	.prefix			= "ITS-",
 	.init_dev_msi_info	= its_init_dev_msi_info,
+};
+
+const struct msi_parent_ops gic_v5_its_msi_parent_ops = {
+	.supported_flags	= ITS_MSI_FLAGS_SUPPORTED,
+	.required_flags		= ITS_MSI_FLAGS_REQUIRED,
+	.chip_flags		= MSI_CHIP_FLAG_SET_EOI,
+	.bus_select_token	= DOMAIN_BUS_NEXUS,
+	.bus_select_mask	= MATCH_PCI_MSI | MATCH_PLATFORM_MSI,
+	.prefix			= "ITS-v5-",
+	.init_dev_msi_info	= its_v5_init_dev_msi_info,
 };

drivers/irqchip/irq-gic-its-msi-parent.h

···
 #define _IRQ_GIC_ITS_MSI_PARENT_H
 
 extern const struct msi_parent_ops gic_v3_its_msi_parent_ops;
+extern const struct msi_parent_ops gic_v5_its_msi_parent_ops;
 
 #endif /* _IRQ_GIC_ITS_MSI_PARENT_H */

drivers/irqchip/irq-gic-v5-irs.c

···
 					GICV5_IRS_CR0_IDLE, NULL);
 }
 
+void gicv5_irs_syncr(void)
+{
+	struct gicv5_irs_chip_data *irs_data;
+	u32 syncr;
+
+	irs_data = list_first_entry_or_null(&irs_nodes, struct gicv5_irs_chip_data, entry);
+	if (WARN_ON_ONCE(!irs_data))
+		return;
+
+	syncr = FIELD_PREP(GICV5_IRS_SYNCR_SYNC, 1);
+	irs_writel_relaxed(irs_data, syncr, GICV5_IRS_SYNCR);
+
+	gicv5_wait_for_op(irs_data->irs_base, GICV5_IRS_SYNC_STATUSR,
+			  GICV5_IRS_SYNC_STATUSR_IDLE);
+}
+
 int gicv5_irs_register_cpu(int cpuid)
 {
 	struct gicv5_irs_chip_data *irs_data;
···
 	}
 
 	return 0;
+}
+
+void __init gicv5_irs_its_probe(void)
+{
+	struct gicv5_irs_chip_data *irs_data;
+
+	list_for_each_entry(irs_data, &irs_nodes, entry)
+		gicv5_its_of_probe(to_of_node(irs_data->fwnode));
 }
 
 int __init gicv5_irs_of_probe(struct device_node *parent)

drivers/irqchip/irq-gic-v5-its.c

···
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2024-2025 ARM Limited, All Rights Reserved.
+ */
+
+#define pr_fmt(fmt)	"GICv5 ITS: " fmt
+
+#include <linux/bitmap.h>
+#include <linux/iommu.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/msi.h>
+#include <linux/of.h>
+#include <linux/of_address.h>
+#include <linux/of_irq.h>
+#include <linux/slab.h>
+
+#include <linux/irqchip.h>
+#include <linux/irqchip/arm-gic-v5.h>
+#include <linux/irqchip/irq-msi-lib.h>
+
+#include "irq-gic-its-msi-parent.h"
+
+#define ITS_FLAGS_NON_COHERENT		BIT(0)
+
+struct gicv5_its_chip_data {
+	struct	xarray			its_devices;
+	struct	mutex			dev_alloc_lock;
+	struct	fwnode_handle		*fwnode;
+	struct gicv5_its_devtab_cfg	devtab_cfgr;
+	void	__iomem			*its_base;
+	u32				flags;
+	unsigned int			msi_domain_flags;
+};
+
+struct gicv5_its_dev {
+	struct gicv5_its_chip_data	*its_node;
+	struct gicv5_its_itt_cfg	itt_cfg;
+	unsigned long			*event_map;
+	u32				device_id;
+	u32				num_events;
+	phys_addr_t			its_trans_phys_base;
+};
+
+static u32 its_readl_relaxed(struct gicv5_its_chip_data *its_node, const u32 reg_offset)
+{
+	return readl_relaxed(its_node->its_base + reg_offset);
+}
+
+static void its_writel_relaxed(struct gicv5_its_chip_data *its_node, const u32 val,
+			       const u32 reg_offset)
+{
+	writel_relaxed(val, its_node->its_base + reg_offset);
+}
+
+static void its_writeq_relaxed(struct gicv5_its_chip_data *its_node, const u64 val,
+			       const u32 reg_offset)
+{
+	writeq_relaxed(val, its_node->its_base + reg_offset);
+}
+
+static void gicv5_its_dcache_clean(struct gicv5_its_chip_data *its, void *start,
+				   size_t sz)
+{
+	void *end = start + sz;
+
+	if (its->flags & ITS_FLAGS_NON_COHERENT)
+		dcache_clean_inval_poc((unsigned long)start, (unsigned long)end);
+	else
+		dsb(ishst);
+}
+
+static void its_write_table_entry(struct gicv5_its_chip_data *its, __le64 *entry,
+				  u64 val)
+{
+	WRITE_ONCE(*entry, cpu_to_le64(val));
+	gicv5_its_dcache_clean(its, entry, sizeof(*entry));
+}
+
+#define devtab_cfgr_field(its, f)	\
+	FIELD_GET(GICV5_ITS_DT_CFGR_##f, (its)->devtab_cfgr.cfgr)
+
+static int gicv5_its_cache_sync(struct gicv5_its_chip_data *its)
+{
+	return gicv5_wait_for_op_atomic(its->its_base, GICV5_ITS_STATUSR,
+					GICV5_ITS_STATUSR_IDLE, NULL);
+}
+
+static void gicv5_its_syncr(struct gicv5_its_chip_data *its,
+			    struct gicv5_its_dev *its_dev)
+{
+	u64 syncr;
+
+	syncr = FIELD_PREP(GICV5_ITS_SYNCR_SYNC, 1) |
+		FIELD_PREP(GICV5_ITS_SYNCR_DEVICEID, its_dev->device_id);
+
+	its_writeq_relaxed(its, syncr, GICV5_ITS_SYNCR);
+
+	gicv5_wait_for_op(its->its_base, GICV5_ITS_SYNC_STATUSR, GICV5_ITS_SYNC_STATUSR_IDLE);
+}
+
+/* Number of bits required for each L2 {device/interrupt translation} table size */
+#define ITS_L2SZ_64K_L2_BITS	13
+#define ITS_L2SZ_16K_L2_BITS	11
+#define ITS_L2SZ_4K_L2_BITS	9
+
+static unsigned int gicv5_its_l2sz_to_l2_bits(unsigned int sz)
+{
+	switch (sz) {
+	case GICV5_ITS_DT_ITT_CFGR_L2SZ_64k:
+		return ITS_L2SZ_64K_L2_BITS;
+	case GICV5_ITS_DT_ITT_CFGR_L2SZ_16k:
+		return ITS_L2SZ_16K_L2_BITS;
+	case GICV5_ITS_DT_ITT_CFGR_L2SZ_4k:
+	default:
+		return ITS_L2SZ_4K_L2_BITS;
+	}
+}
+
+static int gicv5_its_itt_cache_inv(struct gicv5_its_chip_data *its, u32 device_id,
+				   u16 event_id)
+{
+	u32 eventr, eidr;
+	u64 didr;
+
+	didr = FIELD_PREP(GICV5_ITS_DIDR_DEVICEID, device_id);
+	eidr = FIELD_PREP(GICV5_ITS_EIDR_EVENTID, event_id);
+	eventr = FIELD_PREP(GICV5_ITS_INV_EVENTR_I, 0x1);
+
+	its_writeq_relaxed(its, didr, GICV5_ITS_DIDR);
+	its_writel_relaxed(its, eidr, GICV5_ITS_EIDR);
+	its_writel_relaxed(its, eventr, GICV5_ITS_INV_EVENTR);
+
+	return gicv5_its_cache_sync(its);
+}
+
+static void gicv5_its_free_itt_linear(struct gicv5_its_dev *its_dev)
+{
+	kfree(its_dev->itt_cfg.linear.itt);
+}
+
+static void gicv5_its_free_itt_two_level(struct gicv5_its_dev *its_dev)
+{
+	unsigned int i, num_ents = its_dev->itt_cfg.l2.num_l1_ents;
+
+	for (i = 0; i < num_ents; i++)
+		kfree(its_dev->itt_cfg.l2.l2ptrs[i]);
+
+	kfree(its_dev->itt_cfg.l2.l2ptrs);
+	kfree(its_dev->itt_cfg.l2.l1itt);
+}
+
+static void gicv5_its_free_itt(struct gicv5_its_dev *its_dev)
+{
+	if (!its_dev->itt_cfg.l2itt)
+		gicv5_its_free_itt_linear(its_dev);
+	else
+		gicv5_its_free_itt_two_level(its_dev);
+}
+
+static int gicv5_its_create_itt_linear(struct gicv5_its_chip_data *its,
+				       struct gicv5_its_dev *its_dev,
+				       unsigned int event_id_bits)
+{
+	unsigned int num_ents = BIT(event_id_bits);
+	__le64 *itt;
+
+	itt = kcalloc(num_ents, sizeof(*itt), GFP_KERNEL);
+	if (!itt)
+		return -ENOMEM;
+
+	its_dev->itt_cfg.linear.itt = itt;
+	its_dev->itt_cfg.linear.num_ents = num_ents;
+	its_dev->itt_cfg.l2itt = false;
+	its_dev->itt_cfg.event_id_bits = event_id_bits;
+
+	gicv5_its_dcache_clean(its, itt, num_ents * sizeof(*itt));
+
+	return 0;
+}
+
+/*
+ * Allocate a two-level ITT. All ITT entries are allocated in one go, unlike
+ * with the device table. Span may be used to limit the second level table
+ * size, where possible.
+ */
+static int gicv5_its_create_itt_two_level(struct gicv5_its_chip_data *its,
+					  struct gicv5_its_dev *its_dev,
+					  unsigned int event_id_bits,
+					  unsigned int itt_l2sz,
+					  unsigned int num_events)
+{
+	unsigned int l1_bits, l2_bits, span, events_per_l2_table;
+	unsigned int i, complete_tables, final_span, num_ents;
+	__le64 *itt_l1, *itt_l2, **l2ptrs;
+	int ret;
+	u64 val;
+
+	ret = gicv5_its_l2sz_to_l2_bits(itt_l2sz);
+	if (ret >= event_id_bits) {
+		pr_debug("Incorrect l2sz (0x%x) for %u EventID bits. Cannot allocate ITT\n",
+			 itt_l2sz, event_id_bits);
+		return -EINVAL;
+	}
+
+	l2_bits = ret;
+
+	l1_bits = event_id_bits - l2_bits;
+
+	num_ents = BIT(l1_bits);
+
+	itt_l1 = kcalloc(num_ents, sizeof(*itt_l1), GFP_KERNEL);
+	if (!itt_l1)
+		return -ENOMEM;
+
+	l2ptrs = kcalloc(num_ents, sizeof(*l2ptrs), GFP_KERNEL);
+	if (!l2ptrs) {
+		kfree(itt_l1);
+		return -ENOMEM;
+	}
+
+	its_dev->itt_cfg.l2.l2ptrs = l2ptrs;
+
+	its_dev->itt_cfg.l2.l2sz = itt_l2sz;
+	its_dev->itt_cfg.l2.l1itt = itt_l1;
+	its_dev->itt_cfg.l2.num_l1_ents = num_ents;
+	its_dev->itt_cfg.l2itt = true;
+	its_dev->itt_cfg.event_id_bits = event_id_bits;
+
+	/*
+	 * Need to determine how many entries there are per L2 - this is based
+	 * on the number of bits in the table.
+	 */
+	events_per_l2_table = BIT(l2_bits);
+	complete_tables = num_events / events_per_l2_table;
+	final_span = order_base_2(num_events % events_per_l2_table);
+
+	for (i = 0; i < num_ents; i++) {
+		size_t l2sz;
+
+		span = i == complete_tables ? final_span : l2_bits;
+
+		itt_l2 = kcalloc(BIT(span), sizeof(*itt_l2), GFP_KERNEL);
+		if (!itt_l2) {
+			ret = -ENOMEM;
+			goto out_free;
+		}
+
+		its_dev->itt_cfg.l2.l2ptrs[i] = itt_l2;
+
+		l2sz = BIT(span) * sizeof(*itt_l2);
+
+		gicv5_its_dcache_clean(its, itt_l2, l2sz);
+
+		val = (virt_to_phys(itt_l2) & GICV5_ITTL1E_L2_ADDR_MASK) |
+		       FIELD_PREP(GICV5_ITTL1E_SPAN, span)		 |
+		       FIELD_PREP(GICV5_ITTL1E_VALID, 0x1);
+
+		WRITE_ONCE(itt_l1[i], cpu_to_le64(val));
+	}
+
+	gicv5_its_dcache_clean(its, itt_l1, num_ents * sizeof(*itt_l1));
+
+	return 0;
+
+out_free:
+	for (i = i - 1; i >= 0; i--)
+		kfree(its_dev->itt_cfg.l2.l2ptrs[i]);
+
+	kfree(its_dev->itt_cfg.l2.l2ptrs);
+	kfree(itt_l1);
+	return ret;
+}
+
+/*
+ * Function to check whether the device table or ITT table support
+ * a two-level table and if so depending on the number of id_bits
+ * requested, determine whether a two-level table is required.
+ *
+ * Return the 2-level size value if a two level table is deemed
+ * necessary.
+ */
+static bool gicv5_its_l2sz_two_level(bool devtab, u32 its_idr1, u8 id_bits, u8 *sz)
+{
+	unsigned int l2_bits, l2_sz;
+
+	if (devtab && !FIELD_GET(GICV5_ITS_IDR1_DT_LEVELS, its_idr1))
+		return false;
+
+	if (!devtab && !FIELD_GET(GICV5_ITS_IDR1_ITT_LEVELS, its_idr1))
+		return false;
+
+	/*
+	 * Pick an L2 size that matches the pagesize; if a match
+	 * is not found, go for the smallest supported l2 size granule.
+	 *
+	 * This ensures that we will always be able to allocate
+	 * contiguous memory at L2.
+	 */
+	switch (PAGE_SIZE) {
+	case SZ_64K:
+		if (GICV5_ITS_IDR1_L2SZ_SUPPORT_64KB(its_idr1)) {
+			l2_sz = GICV5_ITS_DT_ITT_CFGR_L2SZ_64k;
+			break;
+		}
+		fallthrough;
+	case SZ_4K:
+		if (GICV5_ITS_IDR1_L2SZ_SUPPORT_4KB(its_idr1)) {
+			l2_sz = GICV5_ITS_DT_ITT_CFGR_L2SZ_4k;
+			break;
+		}
+		fallthrough;
+	case SZ_16K:
+		if (GICV5_ITS_IDR1_L2SZ_SUPPORT_16KB(its_idr1)) {
+			l2_sz = GICV5_ITS_DT_ITT_CFGR_L2SZ_16k;
+			break;
+		}
+		if (GICV5_ITS_IDR1_L2SZ_SUPPORT_4KB(its_idr1)) {
+			l2_sz = GICV5_ITS_DT_ITT_CFGR_L2SZ_4k;
+			break;
+		}
+		if (GICV5_ITS_IDR1_L2SZ_SUPPORT_64KB(its_idr1)) {
+			l2_sz = GICV5_ITS_DT_ITT_CFGR_L2SZ_64k;
+			break;
+		}
+
+		l2_sz = GICV5_ITS_DT_ITT_CFGR_L2SZ_4k;
+		break;
+	}
+
+	l2_bits = gicv5_its_l2sz_to_l2_bits(l2_sz);
+
+	if (l2_bits > id_bits)
+		return false;
+
+	*sz = l2_sz;
+
+	return true;
+}
+
+static __le64 *gicv5_its_device_get_itte_ref(struct gicv5_its_dev *its_dev,
+					     u16 event_id)
+{
+	unsigned int l1_idx, l2_idx, l2_bits;
+	__le64 *l2_itt;
+
+	if (!its_dev->itt_cfg.l2itt) {
+		__le64 *itt = its_dev->itt_cfg.linear.itt;
+
+		return &itt[event_id];
+	}
+
+	l2_bits = gicv5_its_l2sz_to_l2_bits(its_dev->itt_cfg.l2.l2sz);
+	l1_idx = event_id >> l2_bits;
+	l2_idx = event_id & GENMASK(l2_bits - 1, 0);
+	l2_itt = its_dev->itt_cfg.l2.l2ptrs[l1_idx];
+
+	return &l2_itt[l2_idx];
+}
+
+static int gicv5_its_device_cache_inv(struct gicv5_its_chip_data *its,
+				      struct gicv5_its_dev *its_dev)
+{
+	u32 devicer;
+	u64 didr;
+
+	didr = FIELD_PREP(GICV5_ITS_DIDR_DEVICEID, its_dev->device_id);
+	devicer = FIELD_PREP(GICV5_ITS_INV_DEVICER_I, 0x1)	|
+		  FIELD_PREP(GICV5_ITS_INV_DEVICER_EVENTID_BITS,
+			     its_dev->itt_cfg.event_id_bits)	|
+		  FIELD_PREP(GICV5_ITS_INV_DEVICER_L1, 0x0);
+	its_writeq_relaxed(its, didr, GICV5_ITS_DIDR);
+	its_writel_relaxed(its, devicer, GICV5_ITS_INV_DEVICER);
+
+	return gicv5_its_cache_sync(its);
+}
+
+/*
+ * Allocate a level 2 device table entry, update L1 parent to reference it.
+ * Only used for 2-level device tables, and it is called on demand.
+ */
+static int gicv5_its_alloc_l2_devtab(struct gicv5_its_chip_data *its,
+				     unsigned int l1_index)
+{
+	__le64 *l2devtab, *l1devtab = its->devtab_cfgr.l2.l1devtab;
+	u8 span, l2sz, l2_bits;
+	u64 l1dte;
+
+	if (FIELD_GET(GICV5_DTL1E_VALID, le64_to_cpu(l1devtab[l1_index])))
+		return 0;
+
+	span = FIELD_GET(GICV5_DTL1E_SPAN, le64_to_cpu(l1devtab[l1_index]));
+	l2sz = devtab_cfgr_field(its, L2SZ);
+
+	l2_bits = gicv5_its_l2sz_to_l2_bits(l2sz);
+
+	/*
+	 * Span allows us to create a smaller L2 device table.
+	 * If it is too large, use the number of allowed L2 bits.
+	 */
+	if (span > l2_bits)
+		span = l2_bits;
+
+	l2devtab = kcalloc(BIT(span), sizeof(*l2devtab), GFP_KERNEL);
+	if (!l2devtab)
+		return -ENOMEM;
+
+	its->devtab_cfgr.l2.l2ptrs[l1_index] = l2devtab;
+
+	l1dte = FIELD_PREP(GICV5_DTL1E_SPAN, span)			|
+		(virt_to_phys(l2devtab) & GICV5_DTL1E_L2_ADDR_MASK)	|
+		FIELD_PREP(GICV5_DTL1E_VALID, 0x1);
+	its_write_table_entry(its, &l1devtab[l1_index], l1dte);
+
+	return 0;
+}
+
+static __le64 *gicv5_its_devtab_get_dte_ref(struct gicv5_its_chip_data *its,
+					    u32 device_id, bool alloc)
+{
+	u8 str = devtab_cfgr_field(its, STRUCTURE);
+	unsigned int l2sz, l2_bits, l1_idx, l2_idx;
+	__le64 *l2devtab;
+	int ret;
+
+	if (str == GICV5_ITS_DT_ITT_CFGR_STRUCTURE_LINEAR) {
+		l2devtab = its->devtab_cfgr.linear.devtab;
+		return &l2devtab[device_id];
+	}
+
+	l2sz = devtab_cfgr_field(its, L2SZ);
+	l2_bits = gicv5_its_l2sz_to_l2_bits(l2sz);
+	l1_idx = device_id >> l2_bits;
+	l2_idx = device_id & GENMASK(l2_bits - 1, 0);
+
+	if (alloc) {
+		/*
+		 * Allocate a new L2 device table here before
+		 * continuing. We make the assumption that the span in
+		 * the L1 table has been set correctly, and blindly use
+		 * that value.
+		 */
+		ret = gicv5_its_alloc_l2_devtab(its, l1_idx);
+		if (ret)
+			return NULL;
+	}
+
+	l2devtab = its->devtab_cfgr.l2.l2ptrs[l1_idx];
+	return &l2devtab[l2_idx];
+}
+
+/*
+ * Register a new device in the device table. Allocate an ITT and
+ * program the L2DTE entry according to the ITT structure that
+ * was chosen.
+ */
+static int gicv5_its_device_register(struct gicv5_its_chip_data *its,
+				     struct gicv5_its_dev *its_dev)
+{
+	u8 event_id_bits, device_id_bits, itt_struct, itt_l2sz;
+	phys_addr_t itt_phys_base;
+	bool two_level_itt;
+	u32 idr1, idr2;
+	__le64 *dte;
+	u64 val;
+	int ret;
+
+	device_id_bits = devtab_cfgr_field(its, DEVICEID_BITS);
+
+	if (its_dev->device_id >= BIT(device_id_bits)) {
+		pr_err("Supplied DeviceID (%u) outside of Device Table range (%u)!",
+		       its_dev->device_id, (u32)GENMASK(device_id_bits - 1, 0));
+		return -EINVAL;
+	}
+
+	dte = gicv5_its_devtab_get_dte_ref(its, its_dev->device_id, true);
+	if (!dte)
+		return -ENOMEM;
+
+	if (FIELD_GET(GICV5_DTL2E_VALID, le64_to_cpu(*dte)))
+		return -EBUSY;
+
+	/*
+	 * Determine how many bits we need, validate those against the max.
+	 * Based on these, determine if we should go for a 1- or 2-level ITT.
+	 */
+	event_id_bits = order_base_2(its_dev->num_events);
+
+	idr2 = its_readl_relaxed(its, GICV5_ITS_IDR2);
+
+	if (event_id_bits > FIELD_GET(GICV5_ITS_IDR2_EVENTID_BITS, idr2)) {
+		pr_err("Required EventID bits (%u) larger than supported bits (%u)!",
+		       event_id_bits,
+		       (u8)FIELD_GET(GICV5_ITS_IDR2_EVENTID_BITS, idr2));
+		return -EINVAL;
+	}
+
+	idr1 = its_readl_relaxed(its, GICV5_ITS_IDR1);
+
+	/*
+	 * L2 ITT size is programmed into the L2DTE regardless of
+	 * whether a two-level or linear ITT is built, init it.
+	 */
+	itt_l2sz = 0;
+
+	two_level_itt = gicv5_its_l2sz_two_level(false, idr1, event_id_bits,
+						  &itt_l2sz);
+	if (two_level_itt)
+		ret = gicv5_its_create_itt_two_level(its, its_dev, event_id_bits,
+						     itt_l2sz,
+						     its_dev->num_events);
+	else
+		ret = gicv5_its_create_itt_linear(its, its_dev, event_id_bits);
+	if (ret)
+		return ret;
+
+	itt_phys_base = two_level_itt ? virt_to_phys(its_dev->itt_cfg.l2.l1itt) :
+					virt_to_phys(its_dev->itt_cfg.linear.itt);
+
+	itt_struct = two_level_itt ? GICV5_ITS_DT_ITT_CFGR_STRUCTURE_TWO_LEVEL :
+				     GICV5_ITS_DT_ITT_CFGR_STRUCTURE_LINEAR;
+
+	val = FIELD_PREP(GICV5_DTL2E_EVENT_ID_BITS, event_id_bits)	|
+	      FIELD_PREP(GICV5_DTL2E_ITT_STRUCTURE, itt_struct)		|
+	      (itt_phys_base & GICV5_DTL2E_ITT_ADDR_MASK)		|
+	      FIELD_PREP(GICV5_DTL2E_ITT_L2SZ, itt_l2sz)		|
+	      FIELD_PREP(GICV5_DTL2E_VALID, 0x1);
+
+	its_write_table_entry(its, dte, val);
+
+	ret = gicv5_its_device_cache_inv(its, its_dev);
+	if (ret) {
+		its_write_table_entry(its, dte, 0);
+		gicv5_its_free_itt(its_dev);
+		return ret;
+	}
+
+	return 0;
+}
+
+/*
+ * Unregister a device in the device table. Lookup the device by ID, free the
+ * corresponding ITT, mark the device as invalid in the device table.
+ */
+static int gicv5_its_device_unregister(struct gicv5_its_chip_data *its,
+				       struct gicv5_its_dev *its_dev)
+{
+	__le64 *dte;
+
+	dte = gicv5_its_devtab_get_dte_ref(its, its_dev->device_id, false);
+
+	if (!FIELD_GET(GICV5_DTL2E_VALID, le64_to_cpu(*dte))) {
+		pr_debug("Device table entry for DeviceID 0x%x is not valid. Nothing to clean up!",
+			 its_dev->device_id);
+		return -EINVAL;
+	}
+
+	/* Zero everything - make it clear that this is an invalid entry */
+	its_write_table_entry(its, dte, 0);
+
+	gicv5_its_free_itt(its_dev);
+
+	return gicv5_its_device_cache_inv(its, its_dev);
+}
+
+/*
+ * Allocate a 1-level device table. All entries are allocated, but marked
+ * invalid.
+ */
+static int gicv5_its_alloc_devtab_linear(struct gicv5_its_chip_data *its,
+					u8 device_id_bits)
+{
+	__le64 *devtab;
+	size_t sz;
+	u64 baser;
+	u32 cfgr;
+
+	/*
+	 * We expect a GICv5 implementation requiring a large number of
+	 * deviceID bits to support a 2-level device table. If that's not
+	 * the case, cap the number of deviceIDs supported according to the
+	 * kmalloc limits so that the system can chug along with a linear
+	 * device table.
+	 */
+	sz = BIT_ULL(device_id_bits) * sizeof(*devtab);
+	if (sz > KMALLOC_MAX_SIZE) {
+		u8 device_id_cap = ilog2(KMALLOC_MAX_SIZE/sizeof(*devtab));
+
+		pr_warn("Limiting device ID bits from %u to %u\n",
+			device_id_bits, device_id_cap);
+		device_id_bits = device_id_cap;
+	}
+
+	devtab = kcalloc(BIT(device_id_bits), sizeof(*devtab), GFP_KERNEL);
+	if (!devtab)
+		return -ENOMEM;
+
+	gicv5_its_dcache_clean(its, devtab, sz);
+
+	cfgr = FIELD_PREP(GICV5_ITS_DT_CFGR_STRUCTURE,
+			  GICV5_ITS_DT_ITT_CFGR_STRUCTURE_LINEAR)	|
+	       FIELD_PREP(GICV5_ITS_DT_CFGR_L2SZ, 0)			|
+	       FIELD_PREP(GICV5_ITS_DT_CFGR_DEVICEID_BITS, device_id_bits);
+	its_writel_relaxed(its, cfgr, GICV5_ITS_DT_CFGR);
+
+	baser = virt_to_phys(devtab) & GICV5_ITS_DT_BASER_ADDR_MASK;
+	its_writeq_relaxed(its, baser, GICV5_ITS_DT_BASER);
+
+	its->devtab_cfgr.cfgr = cfgr;
+	its->devtab_cfgr.linear.devtab = devtab;
+
+	return 0;
+}
+
+/*
+ * Allocate a 2-level device table. L2 entries are not allocated,
+ * they are allocated on-demand.
+ */
+static int gicv5_its_alloc_devtab_two_level(struct gicv5_its_chip_data *its,
+					    u8 device_id_bits,
+					    u8 devtab_l2sz)
+{
+	unsigned int l1_bits, l2_bits, i;
+	__le64 *l1devtab, **l2ptrs;
+	size_t l1_sz;
+	u64 baser;
+	u32 cfgr;
+
+	l2_bits = gicv5_its_l2sz_to_l2_bits(devtab_l2sz);
+
+	l1_bits = device_id_bits - l2_bits;
+	l1_sz = BIT(l1_bits) * sizeof(*l1devtab);
+	/*
+	 * With 2-level device table support it is highly unlikely
+	 * that we are not able to allocate the required amount of
+	 * device table memory to cover deviceID space; cap the
+	 * deviceID space if we encounter such set-up.
+	 * If this ever becomes a problem we could revisit the policy
+	 * behind level 2 size selection to reduce level-1 deviceID bits.
+	 */
+	if (l1_sz > KMALLOC_MAX_SIZE) {
+		l1_bits = ilog2(KMALLOC_MAX_SIZE/sizeof(*l1devtab));
+
+		pr_warn("Limiting device ID bits from %u to %u\n",
+			device_id_bits, l1_bits + l2_bits);
+		device_id_bits = l1_bits + l2_bits;
+		l1_sz = KMALLOC_MAX_SIZE;
+	}
+
+	l1devtab = kcalloc(BIT(l1_bits), sizeof(*l1devtab), GFP_KERNEL);
+	if (!l1devtab)
+		return -ENOMEM;
+
+	l2ptrs = kcalloc(BIT(l1_bits), sizeof(*l2ptrs), GFP_KERNEL);
+	if (!l2ptrs) {
+		kfree(l1devtab);
+		return -ENOMEM;
+	}
+
+	for (i = 0; i < BIT(l1_bits); i++)
+		l1devtab[i] = cpu_to_le64(FIELD_PREP(GICV5_DTL1E_SPAN, l2_bits));
+
+	gicv5_its_dcache_clean(its, l1devtab, l1_sz);
+
+	cfgr = FIELD_PREP(GICV5_ITS_DT_CFGR_STRUCTURE,
+			  GICV5_ITS_DT_ITT_CFGR_STRUCTURE_TWO_LEVEL)	|
+	       FIELD_PREP(GICV5_ITS_DT_CFGR_L2SZ, devtab_l2sz)		|
+	       FIELD_PREP(GICV5_ITS_DT_CFGR_DEVICEID_BITS, device_id_bits);
+	its_writel_relaxed(its, cfgr, GICV5_ITS_DT_CFGR);
+
+	baser = virt_to_phys(l1devtab) & GICV5_ITS_DT_BASER_ADDR_MASK;
+	its_writeq_relaxed(its, baser, GICV5_ITS_DT_BASER);
+
+	its->devtab_cfgr.cfgr = cfgr;
+	its->devtab_cfgr.l2.l1devtab = l1devtab;
+	its->devtab_cfgr.l2.l2ptrs = l2ptrs;
+
+	return 0;
+}
+
+/*
+ * Initialise the device table as either 1- or 2-level depending on what is
+ * supported by the hardware.
+ */
+static int gicv5_its_init_devtab(struct gicv5_its_chip_data *its)
+{
+	u8 device_id_bits, devtab_l2sz;
+	bool two_level_devtab;
+	u32 idr1;
+
+	idr1 = its_readl_relaxed(its, GICV5_ITS_IDR1);
+
+	device_id_bits = FIELD_GET(GICV5_ITS_IDR1_DEVICEID_BITS, idr1);
+	two_level_devtab = gicv5_its_l2sz_two_level(true, idr1, device_id_bits,
+						    &devtab_l2sz);
+	if (two_level_devtab)
+		return gicv5_its_alloc_devtab_two_level(its, device_id_bits,
+						       devtab_l2sz);
+	else
+		return gicv5_its_alloc_devtab_linear(its, device_id_bits);
+}
+
+static void gicv5_its_deinit_devtab(struct gicv5_its_chip_data *its)
+{
+	u8 str = devtab_cfgr_field(its, STRUCTURE);
+
+	if (str == GICV5_ITS_DT_ITT_CFGR_STRUCTURE_LINEAR) {
+		kfree(its->devtab_cfgr.linear.devtab);
+	} else {
+		kfree(its->devtab_cfgr.l2.l1devtab);
+		kfree(its->devtab_cfgr.l2.l2ptrs);
+	}
+}
+
+static void gicv5_its_compose_msi_msg(struct irq_data *d, struct msi_msg *msg)
+{
+	struct gicv5_its_dev *its_dev = irq_data_get_irq_chip_data(d);
+	u64 addr = its_dev->its_trans_phys_base;
+
+	msg->data = FIELD_GET(GICV5_ITS_HWIRQ_EVENT_ID, d->hwirq);
+	msi_msg_set_addr(irq_data_get_msi_desc(d), msg, addr);
+}
+
+static const struct irq_chip gicv5_its_irq_chip = {
+	.name			= "GICv5-ITS-MSI",
+	.irq_mask		= irq_chip_mask_parent,
+	.irq_unmask		= irq_chip_unmask_parent,
+	.irq_eoi		= irq_chip_eoi_parent,
+	.irq_set_affinity	= irq_chip_set_affinity_parent,
+	.irq_get_irqchip_state	= irq_chip_get_parent_state,
+	.irq_set_irqchip_state	= irq_chip_set_parent_state,
+	.irq_compose_msi_msg	= gicv5_its_compose_msi_msg,
+};
+
+static struct gicv5_its_dev *gicv5_its_find_device(struct gicv5_its_chip_data *its,
+						   u32 device_id)
+{
+	struct gicv5_its_dev *dev = xa_load(&its->its_devices, device_id);
+
+	return dev ? dev : ERR_PTR(-ENODEV);
+}
+
+static struct gicv5_its_dev *gicv5_its_alloc_device(struct gicv5_its_chip_data *its, int nvec,
+						    u32 dev_id)
+{
+	struct gicv5_its_dev *its_dev;
+	void *entry;
+	int ret;
+
+	its_dev = gicv5_its_find_device(its, dev_id);
+	if (!IS_ERR(its_dev)) {
+		pr_err("A device with this DeviceID (0x%x) has already been registered.\n",
+		       dev_id);
+
+		return ERR_PTR(-EBUSY);
+	}
+
+	its_dev = kzalloc(sizeof(*its_dev), GFP_KERNEL);
+	if (!its_dev)
+		return ERR_PTR(-ENOMEM);
+
+	its_dev->device_id = dev_id;
+	its_dev->num_events = nvec;
+
+	ret = gicv5_its_device_register(its, its_dev);
+	if (ret) {
+		pr_err("Failed to register the device\n");
+		goto out_dev_free;
+	}
+
+	gicv5_its_device_cache_inv(its, its_dev);
+
+	its_dev->its_node = its;
+
+	its_dev->event_map = (unsigned long *)bitmap_zalloc(its_dev->num_events, GFP_KERNEL);
+	if (!its_dev->event_map) {
+		ret = -ENOMEM;
+		goto out_unregister;
+	}
+
+	entry = xa_store(&its->its_devices, dev_id, its_dev, GFP_KERNEL);
+	if (xa_is_err(entry)) {
+		ret = xa_err(entry);
+		goto out_bitmap_free;
+	}
+
+	return its_dev;
+
+out_bitmap_free:
+	bitmap_free(its_dev->event_map);
+out_unregister:
+	gicv5_its_device_unregister(its, its_dev);
+out_dev_free:
+	kfree(its_dev);
+	return ERR_PTR(ret);
+}
+
+static int gicv5_its_msi_prepare(struct irq_domain *domain, struct device *dev,
+				 int nvec, msi_alloc_info_t *info)
+{
+	u32 dev_id = info->scratchpad[0].ul;
+	struct msi_domain_info *msi_info;
+	struct gicv5_its_chip_data *its;
+	struct gicv5_its_dev *its_dev;
+
+	msi_info = msi_get_domain_info(domain);
+	its = msi_info->data;
+
+	guard(mutex)(&its->dev_alloc_lock);
+
+	its_dev = gicv5_its_alloc_device(its, nvec, dev_id);
+	if (IS_ERR(its_dev))
+		return PTR_ERR(its_dev);
+
+	its_dev->its_trans_phys_base = info->scratchpad[1].ul;
+	info->scratchpad[0].ptr = its_dev;
+
+	return 0;
+}
+
+static void gicv5_its_msi_teardown(struct irq_domain *domain, msi_alloc_info_t *info)
+{
+	struct gicv5_its_dev *its_dev = info->scratchpad[0].ptr;
+	struct msi_domain_info *msi_info;
+	struct gicv5_its_chip_data *its;
+
+	msi_info = msi_get_domain_info(domain);
+	its = msi_info->data;
+
+	guard(mutex)(&its->dev_alloc_lock);
+
+	if (WARN_ON_ONCE(!bitmap_empty(its_dev->event_map, its_dev->num_events)))
+		return;
+
+	xa_erase(&its->its_devices, its_dev->device_id);
+	bitmap_free(its_dev->event_map);
+	gicv5_its_device_unregister(its, its_dev);
+	kfree(its_dev);
+}
+
+static struct msi_domain_ops gicv5_its_msi_domain_ops = {
+	.msi_prepare	= gicv5_its_msi_prepare,
+	.msi_teardown	= gicv5_its_msi_teardown,
+};
+
+static int gicv5_its_map_event(struct gicv5_its_dev *its_dev, u16 event_id, u32 lpi)
+{
+	struct gicv5_its_chip_data *its = its_dev->its_node;
+	u64 itt_entry;
+	__le64 *itte;
+
+	itte = gicv5_its_device_get_itte_ref(its_dev, event_id);
+
+	if (FIELD_GET(GICV5_ITTL2E_VALID, *itte))
+		return -EEXIST;
+
+	itt_entry = FIELD_PREP(GICV5_ITTL2E_LPI_ID, lpi) |
+		    FIELD_PREP(GICV5_ITTL2E_VALID, 0x1);
+
+	its_write_table_entry(its, itte, itt_entry);
+
+	gicv5_its_itt_cache_inv(its, its_dev->device_id, event_id);
+
+	return 0;
+}
+
+static void gicv5_its_unmap_event(struct gicv5_its_dev *its_dev, u16 event_id)
+{
+	struct gicv5_its_chip_data *its = its_dev->its_node;
+	u64 itte_val;
+	__le64 *itte;
+
+	itte = gicv5_its_device_get_itte_ref(its_dev, event_id);
+
+	itte_val = le64_to_cpu(*itte);
+	itte_val &= ~GICV5_ITTL2E_VALID;
+
+	its_write_table_entry(its, itte, itte_val);
+
+	gicv5_its_itt_cache_inv(its, its_dev->device_id, event_id);
+}
+
+static int gicv5_its_alloc_eventid(struct gicv5_its_dev *its_dev,
+				   unsigned int nr_irqs, u32 *eventid)
+{
+	int ret;
+
+	ret = bitmap_find_free_region(its_dev->event_map,
+				      its_dev->num_events,
+				      get_count_order(nr_irqs));
+
+	if (ret < 0)
+		return ret;
+
+	*eventid = ret;
+
+	return 0;
+}
+
+static void gicv5_its_free_eventid(struct gicv5_its_dev *its_dev, u32 event_id_base,
+				   unsigned int nr_irqs)
+{
+	bitmap_release_region(its_dev->event_map, event_id_base,
+			      get_count_order(nr_irqs));
+}
+
+static int gicv5_its_irq_domain_alloc(struct irq_domain *domain, unsigned int virq,
+				      unsigned int nr_irqs, void *arg)
+{
+	u32 device_id, event_id_base, lpi;
+	struct gicv5_its_dev *its_dev;
+	msi_alloc_info_t *info = arg;
+	irq_hw_number_t hwirq;
+	struct irq_data *irqd;
+	int ret, i;
+
+	its_dev = info->scratchpad[0].ptr;
+
+	ret = gicv5_its_alloc_eventid(its_dev, nr_irqs, &event_id_base);
+	if (ret)
+		return ret;
+
+	ret = iommu_dma_prepare_msi(info->desc, its_dev->its_trans_phys_base);
+	if (ret)
+		goto out_eventid;
+
+	device_id = its_dev->device_id;
+
+	for (i = 0; i < nr_irqs; i++) {
+		lpi = gicv5_alloc_lpi();
+		if (ret < 0) {
+			pr_debug("Failed to find free LPI!\n");
+			goto out_eventid;
+		}
+
+		ret = irq_domain_alloc_irqs_parent(domain, virq + i, 1, &lpi);
+		if (ret)
+			goto out_free_lpi;
+
+		/*
+		 * Store eventid and deviceid into the hwirq for later use.
+		 *
+		 *	hwirq  = event_id << 32 | device_id
+		 */
+		hwirq = FIELD_PREP(GICV5_ITS_HWIRQ_DEVICE_ID, device_id) |
+			FIELD_PREP(GICV5_ITS_HWIRQ_EVENT_ID, (u64)event_id_base + i);
+		irq_domain_set_info(domain, virq + i, hwirq,
+				    &gicv5_its_irq_chip, its_dev,
+				    handle_fasteoi_irq, NULL, NULL);
+
+		irqd = irq_get_irq_data(virq + i);
+		irqd_set_single_target(irqd);
+		irqd_set_affinity_on_activate(irqd);
+		irqd_set_resend_when_in_progress(irqd);
+	}
+
+	return 0;
+
+out_free_lpi:
+	gicv5_free_lpi(lpi);
+out_eventid:
+	gicv5_its_free_eventid(its_dev, event_id_base, nr_irqs);
+	return ret;
+}
+
+static void gicv5_its_irq_domain_free(struct irq_domain *domain, unsigned int virq,
+				      unsigned int nr_irqs)
+{
+	struct irq_data *d = irq_domain_get_irq_data(domain, virq);
+	struct gicv5_its_chip_data *its;
+	struct gicv5_its_dev *its_dev;
+	u16 event_id_base;
+	unsigned int i;
+
+	its_dev = irq_data_get_irq_chip_data(d);
+	its = its_dev->its_node;
+
+	event_id_base = FIELD_GET(GICV5_ITS_HWIRQ_EVENT_ID, d->hwirq);
+
+	bitmap_release_region(its_dev->event_map, event_id_base,
+			      get_count_order(nr_irqs));
+
+	/*  Hierarchically free irq data */
+	for (i = 0; i < nr_irqs; i++) {
+		d = irq_domain_get_irq_data(domain, virq + i);
+
+		gicv5_free_lpi(d->parent_data->hwirq);
+		irq_domain_reset_irq_data(d);
+		irq_domain_free_irqs_parent(domain, virq + i, 1);
+	}
+
+	gicv5_its_syncr(its, its_dev);
+	gicv5_irs_syncr();
+}
+
+static int gicv5_its_irq_domain_activate(struct irq_domain *domain, struct irq_data *d,
+					 bool reserve)
+{
+	struct gicv5_its_dev *its_dev = irq_data_get_irq_chip_data(d);
+	u16 event_id;
+	u32 lpi;
+
+	event_id = FIELD_GET(GICV5_ITS_HWIRQ_EVENT_ID, d->hwirq);
+	lpi = d->parent_data->hwirq;
+
+	return gicv5_its_map_event(its_dev, event_id, lpi);
+}
+
+static void gicv5_its_irq_domain_deactivate(struct irq_domain *domain,
+					    struct irq_data *d)
+{
+	struct gicv5_its_dev *its_dev = irq_data_get_irq_chip_data(d);
+	u16 event_id;
+
+	event_id = FIELD_GET(GICV5_ITS_HWIRQ_EVENT_ID, d->hwirq);
+
+	gicv5_its_unmap_event(its_dev, event_id);
+}
+
+static const struct irq_domain_ops gicv5_its_irq_domain_ops = {
+	.alloc		= gicv5_its_irq_domain_alloc,
+	.free		= gicv5_its_irq_domain_free,
+	.activate	= gicv5_its_irq_domain_activate,
+	.deactivate	= gicv5_its_irq_domain_deactivate,
+	.select		= msi_lib_irq_domain_select,
+};
+
+static int gicv5_its_write_cr0(struct gicv5_its_chip_data *its, bool enable)
+{
+	u32 cr0 = FIELD_PREP(GICV5_ITS_CR0_ITSEN, enable);
+
+	its_writel_relaxed(its, cr0, GICV5_ITS_CR0);
+	return gicv5_wait_for_op_atomic(its->its_base, GICV5_ITS_CR0,
+					GICV5_ITS_CR0_IDLE, NULL);
+}
+
+static int gicv5_its_enable(struct gicv5_its_chip_data *its)
+{
+	return gicv5_its_write_cr0(its, true);
+}
+
+static int gicv5_its_disable(struct gicv5_its_chip_data *its)
+{
+	return gicv5_its_write_cr0(its, false);
+}
+
+static void gicv5_its_print_info(struct gicv5_its_chip_data *its_node)
+{
+	bool devtab_linear;
+	u8 device_id_bits;
+	u8 str;
+
+	device_id_bits = devtab_cfgr_field(its_node, DEVICEID_BITS);
+
+	str = devtab_cfgr_field(its_node, STRUCTURE);
+	devtab_linear = (str == GICV5_ITS_DT_ITT_CFGR_STRUCTURE_LINEAR);
+
+	pr_info("ITS %s enabled using %s device table device_id_bits %u\n",
+		fwnode_get_name(its_node->fwnode),
+		devtab_linear ? "linear" : "2-level",
+		device_id_bits);
+}
+
+static int gicv5_its_init_domain(struct gicv5_its_chip_data *its, struct irq_domain *parent)
+{
+	struct irq_domain_info dom_info = {
+		.fwnode		= its->fwnode,
+		.ops		= &gicv5_its_irq_domain_ops,
+		.domain_flags	= its->msi_domain_flags,
+		.parent		= parent,
+	};
+	struct msi_domain_info *info;
+
+	info = kzalloc(sizeof(*info), GFP_KERNEL);
+	if (!info)
+		return -ENOMEM;
+
+	info->ops = &gicv5_its_msi_domain_ops;
+	info->data = its;
+	dom_info.host_data = info;
+
+	if (!msi_create_parent_irq_domain(&dom_info, &gic_v5_its_msi_parent_ops)) {
+		kfree(info);
+		return -ENOMEM;
+	}
+
+	return 0;
+}
+
+static int __init gicv5_its_init_bases(void __iomem *its_base, struct fwnode_handle *handle,
+				       struct irq_domain *parent_domain)
+{
+	struct device_node *np = to_of_node(handle);
+	struct gicv5_its_chip_data *its_node;
+	u32 cr0, cr1;
+	bool enabled;
+	int ret;
+
+	its_node = kzalloc(sizeof(*its_node), GFP_KERNEL);
+	if (!its_node)
+		return -ENOMEM;
+
+	mutex_init(&its_node->dev_alloc_lock);
+	xa_init(&its_node->its_devices);
+	its_node->fwnode = handle;
+	its_node->its_base = its_base;
+	its_node->msi_domain_flags = IRQ_DOMAIN_FLAG_ISOLATED_MSI |
+				     IRQ_DOMAIN_FLAG_FWNODE_PARENT;
+
+	cr0 = its_readl_relaxed(its_node, GICV5_ITS_CR0);
+	enabled = FIELD_GET(GICV5_ITS_CR0_ITSEN, cr0);
+	if (WARN(enabled, "ITS %s enabled, disabling it before proceeding\n", np->full_name)) {
+		ret = gicv5_its_disable(its_node);
+		if (ret)
+			goto out_free_node;
+	}
+
+	if (of_property_read_bool(np, "dma-noncoherent")) {
+		/*
+		 * A non-coherent ITS implies that some cache levels cannot be
+		 * used coherently by the cores and GIC. Our only option is to mark
+		 * memory attributes for the GIC as non-cacheable; by default,
+		 * non-cacheable memory attributes imply outer-shareable
+		 * shareability, the value written into ITS_CR1_SH is ignored.
+		 */
+		cr1 = FIELD_PREP(GICV5_ITS_CR1_ITT_RA, GICV5_NO_READ_ALLOC)	|
+		      FIELD_PREP(GICV5_ITS_CR1_DT_RA, GICV5_NO_READ_ALLOC)	|
+		      FIELD_PREP(GICV5_ITS_CR1_IC, GICV5_NON_CACHE)		|
+		      FIELD_PREP(GICV5_ITS_CR1_OC, GICV5_NON_CACHE);
+		its_node->flags |= ITS_FLAGS_NON_COHERENT;
+	} else {
+		cr1 = FIELD_PREP(GICV5_ITS_CR1_ITT_RA, GICV5_READ_ALLOC)	|
+		      FIELD_PREP(GICV5_ITS_CR1_DT_RA, GICV5_READ_ALLOC)		|
+		      FIELD_PREP(GICV5_ITS_CR1_IC, GICV5_WB_CACHE)		|
+		      FIELD_PREP(GICV5_ITS_CR1_OC, GICV5_WB_CACHE)		|
+		      FIELD_PREP(GICV5_ITS_CR1_SH, GICV5_INNER_SHARE);
+	}
+
+	its_writel_relaxed(its_node, cr1, GICV5_ITS_CR1);
+
+	ret = gicv5_its_init_devtab(its_node);
+	if (ret)
+		goto out_free_node;
+
+	ret = gicv5_its_enable(its_node);
+	if (ret)
+		goto out_free_devtab;
+
+	ret = gicv5_its_init_domain(its_node, parent_domain);
+	if (ret)
+		goto out_disable_its;
+
+	gicv5_its_print_info(its_node);
+
+	return 0;
+
+out_disable_its:
+	gicv5_its_disable(its_node);
+out_free_devtab:
+	gicv5_its_deinit_devtab(its_node);
+out_free_node:
+	kfree(its_node);
+	return ret;
+}
+
+static int __init gicv5_its_init(struct device_node *node)
+{
+	void __iomem *its_base;
+	int ret, idx;
+
+	idx = of_property_match_string(node, "reg-names", "ns-config");
+	if (idx < 0) {
+		pr_err("%pOF: ns-config reg-name not present\n", node);
+		return -ENODEV;
+	}
+
+	its_base = of_io_request_and_map(node, idx, of_node_full_name(node));
+	if (IS_ERR(its_base)) {
+		pr_err("%pOF: unable to map GICv5 ITS_CONFIG_FRAME\n", node);
+		return PTR_ERR(its_base);
+	}
+
+	ret = gicv5_its_init_bases(its_base, of_fwnode_handle(node),
+				   gicv5_global_data.lpi_domain);
+	if (ret)
+		goto out_unmap;
+
+	return 0;
+
+out_unmap:
+	iounmap(its_base);
+	return ret;
+}
+
+void __init gicv5_its_of_probe(struct device_node *parent)
+{
+	struct device_node *np;
+
+	for_each_available_child_of_node(parent, np) {
+		if (!of_device_is_compatible(np, "arm,gic-v5-its"))
+			continue;
+
+		if (gicv5_its_init(np))
+			pr_err("Failed to init ITS %s\n", np->full_name);
+	}
+}

drivers/irqchip/irq-gic-v5.c

···
 
 	gicv5_smp_init();
 
+	gicv5_irs_its_probe();
+
 	return 0;
 
 out_int:

include/linux/irqchip/arm-gic-v5.h

···
 #define GICV5_IRS_IDR7			0x001c
 #define GICV5_IRS_CR0			0x0080
 #define GICV5_IRS_CR1			0x0084
+#define GICV5_IRS_SYNCR			0x00c0
+#define GICV5_IRS_SYNC_STATUSR		0x00c4
 #define GICV5_IRS_SPI_SELR		0x0108
 #define GICV5_IRS_SPI_CFGR		0x0114
 #define GICV5_IRS_SPI_STATUSR		0x0118
···
 #define GICV5_IRS_CR1_OC		GENMASK(3, 2)
 #define GICV5_IRS_CR1_SH		GENMASK(1, 0)
 
+#define GICV5_IRS_SYNCR_SYNC		BIT(31)
+
+#define GICV5_IRS_SYNC_STATUSR_IDLE	BIT(0)
+
 #define GICV5_IRS_SPI_STATUSR_V		BIT(1)
 #define GICV5_IRS_SPI_STATUSR_IDLE	BIT(0)
 
···
 #define GICV5_ISTL1E_VALID		BIT_ULL(0)
 
 #define GICV5_ISTL1E_L2_ADDR_MASK	GENMASK_ULL(55, 12)
+
+/*
+ * ITS registers and tables structures
+ */
+#define GICV5_ITS_IDR1		0x0004
+#define GICV5_ITS_IDR2		0x0008
+#define GICV5_ITS_CR0		0x0080
+#define GICV5_ITS_CR1		0x0084
+#define GICV5_ITS_DT_BASER	0x00c0
+#define GICV5_ITS_DT_CFGR	0x00d0
+#define GICV5_ITS_DIDR		0x0100
+#define GICV5_ITS_EIDR		0x0108
+#define GICV5_ITS_INV_EVENTR	0x010c
+#define GICV5_ITS_INV_DEVICER	0x0110
+#define GICV5_ITS_STATUSR	0x0120
+#define GICV5_ITS_SYNCR		0x0140
+#define GICV5_ITS_SYNC_STATUSR	0x0148
+
+#define GICV5_ITS_IDR1_L2SZ			GENMASK(10, 8)
+#define GICV5_ITS_IDR1_ITT_LEVELS		BIT(7)
+#define GICV5_ITS_IDR1_DT_LEVELS		BIT(6)
+#define GICV5_ITS_IDR1_DEVICEID_BITS		GENMASK(5, 0)
+
+#define GICV5_ITS_IDR1_L2SZ_SUPPORT_4KB(r)	FIELD_GET(BIT(8), (r))
+#define GICV5_ITS_IDR1_L2SZ_SUPPORT_16KB(r)	FIELD_GET(BIT(9), (r))
+#define GICV5_ITS_IDR1_L2SZ_SUPPORT_64KB(r)	FIELD_GET(BIT(10), (r))
+
+#define GICV5_ITS_IDR2_XDMN_EVENTs		GENMASK(6, 5)
+#define GICV5_ITS_IDR2_EVENTID_BITS		GENMASK(4, 0)
+
+#define GICV5_ITS_CR0_IDLE			BIT(1)
+#define GICV5_ITS_CR0_ITSEN			BIT(0)
+
+#define GICV5_ITS_CR1_ITT_RA			BIT(7)
+#define GICV5_ITS_CR1_DT_RA			BIT(6)
+#define GICV5_ITS_CR1_IC			GENMASK(5, 4)
+#define GICV5_ITS_CR1_OC			GENMASK(3, 2)
+#define GICV5_ITS_CR1_SH			GENMASK(1, 0)
+
+#define GICV5_ITS_DT_CFGR_STRUCTURE		BIT(16)
+#define GICV5_ITS_DT_CFGR_L2SZ			GENMASK(7, 6)
+#define GICV5_ITS_DT_CFGR_DEVICEID_BITS		GENMASK(5, 0)
+
+#define GICV5_ITS_DT_BASER_ADDR_MASK		GENMASK_ULL(55, 3)
+
+#define GICV5_ITS_INV_DEVICER_I			BIT(31)
+#define GICV5_ITS_INV_DEVICER_EVENTID_BITS	GENMASK(5, 1)
+#define GICV5_ITS_INV_DEVICER_L1		BIT(0)
+
+#define GICV5_ITS_DIDR_DEVICEID			GENMASK_ULL(31, 0)
+
+#define GICV5_ITS_EIDR_EVENTID			GENMASK(15, 0)
+
+#define GICV5_ITS_INV_EVENTR_I			BIT(31)
+#define GICV5_ITS_INV_EVENTR_ITT_L2SZ		GENMASK(2, 1)
+#define GICV5_ITS_INV_EVENTR_L1			BIT(0)
+
+#define GICV5_ITS_STATUSR_IDLE			BIT(0)
+
+#define GICV5_ITS_SYNCR_SYNC			BIT_ULL(63)
+#define GICV5_ITS_SYNCR_SYNCALL			BIT_ULL(32)
+#define GICV5_ITS_SYNCR_DEVICEID		GENMASK_ULL(31, 0)
+
+#define GICV5_ITS_SYNC_STATUSR_IDLE		BIT(0)
+
+#define GICV5_DTL1E_VALID			BIT_ULL(0)
+/* Note that there is no shift for the address by design */
+#define GICV5_DTL1E_L2_ADDR_MASK		GENMASK_ULL(55, 3)
+#define GICV5_DTL1E_SPAN			GENMASK_ULL(63, 60)
+
+#define GICV5_DTL2E_VALID			BIT_ULL(0)
+#define GICV5_DTL2E_ITT_L2SZ			GENMASK_ULL(2, 1)
+/* Note that there is no shift for the address by design */
+#define GICV5_DTL2E_ITT_ADDR_MASK		GENMASK_ULL(55, 3)
+#define GICV5_DTL2E_ITT_DSWE			BIT_ULL(57)
+#define GICV5_DTL2E_ITT_STRUCTURE		BIT_ULL(58)
+#define GICV5_DTL2E_EVENT_ID_BITS		GENMASK_ULL(63, 59)
+
+#define GICV5_ITTL1E_VALID			BIT_ULL(0)
+/* Note that there is no shift for the address by design */
+#define GICV5_ITTL1E_L2_ADDR_MASK		GENMASK_ULL(55, 3)
+#define GICV5_ITTL1E_SPAN			GENMASK_ULL(63, 60)
+
+#define GICV5_ITTL2E_LPI_ID			GENMASK_ULL(23, 0)
+#define GICV5_ITTL2E_DAC			GENMASK_ULL(29, 28)
+#define GICV5_ITTL2E_VIRTUAL			BIT_ULL(30)
+#define GICV5_ITTL2E_VALID			BIT_ULL(31)
+#define GICV5_ITTL2E_VM_ID			GENMASK_ULL(47, 32)
+
+#define GICV5_ITS_DT_ITT_CFGR_L2SZ_4k		0b00
+#define GICV5_ITS_DT_ITT_CFGR_L2SZ_16k		0b01
+#define GICV5_ITS_DT_ITT_CFGR_L2SZ_64k		0b10
+
+#define GICV5_ITS_DT_ITT_CFGR_STRUCTURE_LINEAR		0
+#define GICV5_ITS_DT_ITT_CFGR_STRUCTURE_TWO_LEVEL	1
+
+#define GICV5_ITS_HWIRQ_DEVICE_ID		GENMASK_ULL(31, 0)
+#define GICV5_ITS_HWIRQ_EVENT_ID		GENMASK_ULL(63, 32)
 
 /*
  * Global Data structures and functions
···
 	return 0;
 }
 
+static inline int gicv5_wait_for_op_s(void __iomem *addr, u32 offset,
+				      const char *reg_s, u32 mask)
+{
+	void __iomem *reg = addr + offset;
+	u32 val;
+	int ret;
+
+	ret = readl_poll_timeout(reg, val, val & mask, 1, 10 * USEC_PER_MSEC);
+	if (unlikely(ret == -ETIMEDOUT)) {
+		pr_err_ratelimited("%s timeout...\n", reg_s);
+		return ret;
+	}
+
+	return 0;
+}
+
 #define gicv5_wait_for_op_atomic(base, reg, mask, val) \
 	gicv5_wait_for_op_s_atomic(base, reg, #reg, mask, val)
+
+#define gicv5_wait_for_op(base, reg, mask) \
+	gicv5_wait_for_op_s(base, reg, #reg, mask)
 
 void __init gicv5_init_lpi_domain(void);
 void __init gicv5_free_lpi_domain(void);
···
 int gicv5_irs_of_probe(struct device_node *parent);
 void gicv5_irs_remove(void);
 int gicv5_irs_enable(void);
+void gicv5_irs_its_probe(void);
 int gicv5_irs_register_cpu(int cpuid);
 int gicv5_irs_cpu_to_iaffid(int cpu_id, u16 *iaffid);
 struct gicv5_irs_chip_data *gicv5_irs_lookup_by_spi_id(u32 spi_id);
 int gicv5_spi_irq_set_type(struct irq_data *d, unsigned int type);
 int gicv5_irs_iste_alloc(u32 lpi);
+void gicv5_irs_syncr(void);
+
+struct gicv5_its_devtab_cfg {
+	union {
+		struct {
+			__le64	*devtab;
+		} linear;
+		struct {
+			__le64	*l1devtab;
+			__le64	**l2ptrs;
+		} l2;
+	};
+	u32	cfgr;
+};
+
+struct gicv5_its_itt_cfg {
+	union {
+		struct {
+			__le64		*itt;
+			unsigned int	num_ents;
+		} linear;
+		struct {
+			__le64		*l1itt;
+			__le64		**l2ptrs;
+			unsigned int	num_l1_ents;
+			u8		l2sz;
+		} l2;
+	};
+	u8	event_id_bits;
+	bool	l2itt;
+};
 
 void gicv5_init_lpis(u32 max);
 void gicv5_deinit_lpis(void);
 
 int gicv5_alloc_lpi(void);
 void gicv5_free_lpi(u32 lpi);
+
+void __init gicv5_its_of_probe(struct device_node *parent);
 #endif