[PATCH v5 4/9] irqchip: Add RISC-V incoming MSI controller driver

[Anup Patel]

The RISC-V advanced interrupt architecture (AIA) specification defines
a new MSI controller for managing MSIs and IPIs on a RISC-V platform.

This new MSI controller is referred to as incoming message signalled
interrupt controller (IMSIC) which manages MSI on per-HART (or per-CPU)
basis. (For more details refer https://github.com/riscv/riscv-aia)

This patch adds an irqchip driver for RISC-V IMSIC which provides
IPIs and platform MSIs to the Linux RISC-V kernel.

Signed-off-by: Anup Patel <apatel@xxxxxxxxxxxxxxxx>
---
 drivers/irqchip/Kconfig             |    7 +-
 drivers/irqchip/Makefile            |    1 +
 drivers/irqchip/irq-riscv-imsic.c   | 1011 +++++++++++++++++++++++++++
 include/linux/irqchip/riscv-imsic.h |   86 +++
 4 files changed, 1104 insertions(+), 1 deletion(-)
 create mode 100644 drivers/irqchip/irq-riscv-imsic.c
 create mode 100644 include/linux/irqchip/riscv-imsic.h

diff --git a/drivers/irqchip/Kconfig b/drivers/irqchip/Kconfig
index 09e422da482f..8ef18be5f37b 100644
--- a/drivers/irqchip/Kconfig
+++ b/drivers/irqchip/Kconfig
@@ -30,7 +30,6 @@ config ARM_GIC_V2M
 
 config GIC_NON_BANKED
 	bool
-
 config ARM_GIC_V3
 	bool
 	select IRQ_DOMAIN_HIERARCHY
@@ -545,6 +544,12 @@ config SIFIVE_PLIC
 	select IRQ_DOMAIN_HIERARCHY
 	select GENERIC_IRQ_EFFECTIVE_AFF_MASK if SMP
 
+config RISCV_IMSIC
+	bool
+	depends on RISCV
+	select IRQ_DOMAIN_HIERARCHY
+	select GENERIC_MSI_IRQ
+
 config EXYNOS_IRQ_COMBINER
 	bool "Samsung Exynos IRQ combiner support" if COMPILE_TEST
 	depends on (ARCH_EXYNOS && ARM) || COMPILE_TEST
diff --git a/drivers/irqchip/Makefile b/drivers/irqchip/Makefile
index ffd945fe71aa..577bde3e986b 100644
--- a/drivers/irqchip/Makefile
+++ b/drivers/irqchip/Makefile
@@ -95,6 +95,7 @@ obj-$(CONFIG_QCOM_MPM)			+= irq-qcom-mpm.o
 obj-$(CONFIG_CSKY_MPINTC)		+= irq-csky-mpintc.o
 obj-$(CONFIG_CSKY_APB_INTC)		+= irq-csky-apb-intc.o
 obj-$(CONFIG_RISCV_INTC)		+= irq-riscv-intc.o
+obj-$(CONFIG_RISCV_IMSIC)		+= irq-riscv-imsic.o
 obj-$(CONFIG_SIFIVE_PLIC)		+= irq-sifive-plic.o
 obj-$(CONFIG_IMX_IRQSTEER)		+= irq-imx-irqsteer.o
 obj-$(CONFIG_IMX_INTMUX)		+= irq-imx-intmux.o
diff --git a/drivers/irqchip/irq-riscv-imsic.c b/drivers/irqchip/irq-riscv-imsic.c
new file mode 100644
index 000000000000..ceb5e0fc883c
--- /dev/null
+++ b/drivers/irqchip/irq-riscv-imsic.c
@@ -0,0 +1,1011 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2021 Western Digital Corporation or its affiliates.
+ * Copyright (C) 2022 Ventana Micro Systems Inc.
+ */
+
+#define pr_fmt(fmt) "riscv-imsic: " fmt
+#include <linux/bitmap.h>
+#include <linux/cpu.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/irq.h>
+#include <linux/irqchip.h>
+#include <linux/irqchip/chained_irq.h>
+#include <linux/irqchip/riscv-imsic.h>
+#include <linux/irqdomain.h>
+#include <linux/module.h>
+#include <linux/msi.h>
+#include <linux/of_address.h>
+#include <linux/platform_device.h>
+#include <linux/spinlock.h>
+#include <linux/smp.h>
+#include <asm/hwcap.h>
+
+#define IMSIC_DISABLE_EIDELIVERY		0
+#define IMSIC_ENABLE_EIDELIVERY			1
+#define IMSIC_DISABLE_EITHRESHOLD		1
+#define IMSIC_ENABLE_EITHRESHOLD		0
+
+/*
+ * The IMSIC driver uses 1 IPI for ID synchronization and
+ * arch/riscv/kernel/smp.c require 6 IPIs so we fix the
+ * total number of IPIs to 8.
+ */
+#define IMSIC_NR_IPI				8
+
+#define imsic_csr_write(__c, __v)		\
+do {						\
+	csr_write(CSR_ISELECT, __c);		\
+	csr_write(CSR_IREG, __v);		\
+} while (0)
+
+#define imsic_csr_read(__c)			\
+({						\
+	unsigned long __v;			\
+	csr_write(CSR_ISELECT, __c);		\
+	__v = csr_read(CSR_IREG);		\
+	__v;					\
+})
+
+#define imsic_csr_set(__c, __v)			\
+do {						\
+	csr_write(CSR_ISELECT, __c);		\
+	csr_set(CSR_IREG, __v);			\
+} while (0)
+
+#define imsic_csr_clear(__c, __v)		\
+do {						\
+	csr_write(CSR_ISELECT, __c);		\
+	csr_clear(CSR_IREG, __v);		\
+} while (0)
+
+struct imsic_priv {
+	/* Global configuration common for all HARTs */
+	struct imsic_global_config global;
+
+	/* Global state of interrupt identities */
+	raw_spinlock_t ids_lock;
+	unsigned long *ids_used_bimap;
+	unsigned long *ids_enabled_bimap;
+	unsigned int *ids_target_cpu;
+
+	/* Mask for connected CPUs */
+	struct cpumask lmask;
+
+	/* IPI interrupt identity and synchronization */
+	u32 ipi_id;
+	int ipi_virq;
+	struct irq_desc *ipi_lsync_desc;
+
+	/* IRQ domains */
+	struct irq_domain *base_domain;
+	struct irq_domain *plat_domain;
+};
+
+static struct imsic_priv *imsic;
+static int imsic_parent_irq;
+
+const struct imsic_global_config *imsic_get_global_config(void)
+{
+	return (imsic) ? &imsic->global : NULL;
+}
+EXPORT_SYMBOL_GPL(imsic_get_global_config);
+
+static int imsic_cpu_page_phys(unsigned int cpu,
+			       unsigned int guest_index,
+			       phys_addr_t *out_msi_pa)
+{
+	struct imsic_global_config *global;
+	struct imsic_local_config *local;
+
+	global = &imsic->global;
+	local = per_cpu_ptr(global->local, cpu);
+
+	if (BIT(global->guest_index_bits) <= guest_index)
+		return -EINVAL;
+
+	if (out_msi_pa)
+		*out_msi_pa = local->msi_pa +
+			      (guest_index * IMSIC_MMIO_PAGE_SZ);
+
+	return 0;
+}
+
+static int imsic_get_cpu(const struct cpumask *mask_val, bool force,
+			 unsigned int *out_target_cpu)
+{
+	struct cpumask amask;
+	unsigned int cpu;
+
+	cpumask_and(&amask, &imsic->lmask, mask_val);
+
+	if (force)
+		cpu = cpumask_first(&amask);
+	else
+		cpu = cpumask_any_and(&amask, cpu_online_mask);
+
+	if (cpu >= nr_cpu_ids)
+		return -EINVAL;
+
+	if (out_target_cpu)
+		*out_target_cpu = cpu;
+
+	return 0;
+}
+
+static void imsic_id_set_target(unsigned int id, unsigned int target_cpu)
+{
+	unsigned long flags;
+
+	raw_spin_lock_irqsave(&imsic->ids_lock, flags);
+	imsic->ids_target_cpu[id] = target_cpu;
+	raw_spin_unlock_irqrestore(&imsic->ids_lock, flags);
+}
+
+static unsigned int imsic_id_get_target(unsigned int id)
+{
+	unsigned int ret;
+	unsigned long flags;
+
+	raw_spin_lock_irqsave(&imsic->ids_lock, flags);
+	ret = imsic->ids_target_cpu[id];
+	raw_spin_unlock_irqrestore(&imsic->ids_lock, flags);
+
+	return ret;
+}
+
+static void __imsic_eix_update(unsigned long base_id,
+			       unsigned long num_id, bool pend, bool val)
+{
+	unsigned long i, isel, ireg;
+	unsigned long id = base_id, last_id = base_id + num_id;
+
+	while (id < last_id) {
+		isel = id / BITS_PER_LONG;
+		isel *= BITS_PER_LONG / IMSIC_EIPx_BITS;
+		isel += (pend) ? IMSIC_EIP0 : IMSIC_EIE0;
+
+		ireg = 0;
+		for (i = id & (__riscv_xlen - 1);
+		     (id < last_id) && (i < __riscv_xlen); i++) {
+			ireg |= BIT(i);
+			id++;
+		}
+
+		/*
+		 * The IMSIC EIEx and EIPx registers are indirectly
+		 * accessed via using ISELECT and IREG CSRs so we
+		 * need to access these CSRs without getting preempted.
+		 *
+		 * All existing users of this function call this
+		 * function with local IRQs disabled so we don't
+		 * need to do anything special here.
+		 */
+		if (val)
+			imsic_csr_set(isel, ireg);
+		else
+			imsic_csr_clear(isel, ireg);
+	}
+}
+
+#define __imsic_id_enable(__id)		\
+	__imsic_eix_update((__id), 1, false, true)
+#define __imsic_id_disable(__id)	\
+	__imsic_eix_update((__id), 1, false, false)
+
+static void imsic_ids_local_sync(void)
+{
+	int i;
+	unsigned long flags;
+
+	raw_spin_lock_irqsave(&imsic->ids_lock, flags);
+	for (i = 1; i <= imsic->global.nr_ids; i++) {
+		if (imsic->ipi_id == i)
+			continue;
+
+		if (test_bit(i, imsic->ids_enabled_bimap))
+			__imsic_id_enable(i);
+		else
+			__imsic_id_disable(i);
+	}
+	raw_spin_unlock_irqrestore(&imsic->ids_lock, flags);
+}
+
+static void imsic_ids_local_delivery(bool enable)
+{
+	if (enable) {
+		imsic_csr_write(IMSIC_EITHRESHOLD, IMSIC_ENABLE_EITHRESHOLD);
+		imsic_csr_write(IMSIC_EIDELIVERY, IMSIC_ENABLE_EIDELIVERY);
+	} else {
+		imsic_csr_write(IMSIC_EIDELIVERY, IMSIC_DISABLE_EIDELIVERY);
+		imsic_csr_write(IMSIC_EITHRESHOLD, IMSIC_DISABLE_EITHRESHOLD);
+	}
+}
+
+#ifdef CONFIG_SMP
+static irqreturn_t imsic_ids_sync_handler(int irq, void *data)
+{
+	imsic_ids_local_sync();
+	return IRQ_HANDLED;
+}
+
+static void imsic_ids_remote_sync(void)
+{
+	struct cpumask amask;
+
+	/*
+	 * We simply inject ID synchronization IPI to all target CPUs
+	 * except current CPU. The ipi_send_mask() implementation of
+	 * IPI mux will inject ID synchronization IPI only for CPUs
+	 * that have enabled it so offline CPUs won't receive IPI.
+	 * An offline CPU will unconditionally synchronize IDs through
+	 * imsic_starting_cpu() when the CPU is brought up.
+	 */
+	cpumask_andnot(&amask, &imsic->lmask, cpumask_of(smp_processor_id()));
+	__ipi_send_mask(imsic->ipi_lsync_desc, &amask);
+}
+#else
+#define imsic_ids_remote_sync()
+#endif
+
+static int imsic_ids_alloc(unsigned int order)
+{
+	int ret;
+	unsigned long flags;
+
+	raw_spin_lock_irqsave(&imsic->ids_lock, flags);
+	ret = bitmap_find_free_region(imsic->ids_used_bimap,
+				      imsic->global.nr_ids + 1, order);
+	raw_spin_unlock_irqrestore(&imsic->ids_lock, flags);
+
+	return ret;
+}
+
+static void imsic_ids_free(unsigned int base_id, unsigned int order)
+{
+	unsigned long flags;
+
+	raw_spin_lock_irqsave(&imsic->ids_lock, flags);
+	bitmap_release_region(imsic->ids_used_bimap, base_id, order);
+	raw_spin_unlock_irqrestore(&imsic->ids_lock, flags);
+}
+
+static int __init imsic_ids_init(void)
+{
+	int i;
+	struct imsic_global_config *global = &imsic->global;
+
+	raw_spin_lock_init(&imsic->ids_lock);
+
+	/* Allocate used bitmap */
+	imsic->ids_used_bimap = bitmap_zalloc(global->nr_ids + 1, GFP_KERNEL);
+	if (!imsic->ids_used_bimap)
+		return -ENOMEM;
+
+	/* Allocate enabled bitmap */
+	imsic->ids_enabled_bimap = bitmap_zalloc(global->nr_ids + 1,
+						GFP_KERNEL);
+	if (!imsic->ids_enabled_bimap) {
+		kfree(imsic->ids_used_bimap);
+		return -ENOMEM;
+	}
+
+	/* Allocate target CPU array */
+	imsic->ids_target_cpu = kcalloc(global->nr_ids + 1,
+				       sizeof(unsigned int), GFP_KERNEL);
+	if (!imsic->ids_target_cpu) {
+		bitmap_free(imsic->ids_enabled_bimap);
+		bitmap_free(imsic->ids_used_bimap);
+		return -ENOMEM;
+	}
+	for (i = 0; i <= global->nr_ids; i++)
+		imsic->ids_target_cpu[i] = UINT_MAX;
+
+	/* Reserve ID#0 because it is special and never implemented */
+	bitmap_set(imsic->ids_used_bimap, 0, 1);
+
+	return 0;
+}
+
+static void __init imsic_ids_cleanup(void)
+{
+	kfree(imsic->ids_target_cpu);
+	bitmap_free(imsic->ids_enabled_bimap);
+	bitmap_free(imsic->ids_used_bimap);
+}
+
+#ifdef CONFIG_SMP
+static void imsic_ipi_send(unsigned int cpu)
+{
+	struct imsic_local_config *local =
+				per_cpu_ptr(imsic->global.local, cpu);
+
+	writel(imsic->ipi_id, local->msi_va);
+}
+
+static void imsic_ipi_starting_cpu(void)
+{
+	/* Enable IPIs for current CPU. */
+	__imsic_id_enable(imsic->ipi_id);
+
+	/* Enable virtual IPI used for IMSIC ID synchronization */
+	enable_percpu_irq(imsic->ipi_virq, 0);
+}
+
+static void imsic_ipi_dying_cpu(void)
+{
+	/*
+	 * Disable virtual IPI used for IMSIC ID synchronization so
+	 * that we don't receive ID synchronization requests.
+	 */
+	disable_percpu_irq(imsic->ipi_virq);
+}
+
+static int __init imsic_ipi_domain_init(void)
+{
+	int virq;
+
+	/* Allocate interrupt identity for IPIs */
+	virq = imsic_ids_alloc(get_count_order(1));
+	if (virq < 0)
+		return virq;
+	imsic->ipi_id = virq;
+
+	/* Create IMSIC IPI multiplexing */
+	virq = ipi_mux_create(IMSIC_NR_IPI, imsic_ipi_send);
+	if (virq <= 0) {
+		imsic_ids_free(imsic->ipi_id, get_count_order(1));
+		return (virq < 0) ? virq : -ENOMEM;
+	}
+	imsic->ipi_virq = virq;
+
+	/* First vIRQ is used for IMSIC ID synchronization */
+	virq = request_percpu_irq(imsic->ipi_virq, imsic_ids_sync_handler,
+				  "riscv-imsic-lsync", imsic->global.local);
+	if (virq) {
+		imsic_ids_free(imsic->ipi_id, get_count_order(1));
+		return virq;
+	}
+	irq_set_status_flags(imsic->ipi_virq, IRQ_HIDDEN);
+	imsic->ipi_lsync_desc = irq_to_desc(imsic->ipi_virq);
+
+	/* Set vIRQ range */
+	riscv_ipi_set_virq_range(imsic->ipi_virq + 1, IMSIC_NR_IPI - 1, true);
+
+	return 0;
+}
+
+static void __init imsic_ipi_domain_cleanup(void)
+{
+	if (imsic->ipi_lsync_desc)
+		free_percpu_irq(imsic->ipi_virq, imsic->global.local);
+	imsic_ids_free(imsic->ipi_id, get_count_order(1));
+}
+#else
+static void imsic_ipi_starting_cpu(void)
+{
+}
+
+static void imsic_ipi_dying_cpu(void)
+{
+}
+
+static int __init imsic_ipi_domain_init(void)
+{
+	/* Clear the IPI id because we are not using IPIs */
+	imsic->ipi_id = 0;
+	return 0;
+}
+
+static void __init imsic_ipi_domain_cleanup(void)
+{
+}
+#endif
+
+static void imsic_irq_mask(struct irq_data *d)
+{
+	unsigned long flags;
+
+	raw_spin_lock_irqsave(&imsic->ids_lock, flags);
+	bitmap_clear(imsic->ids_enabled_bimap, d->hwirq, 1);
+	__imsic_id_disable(d->hwirq);
+	raw_spin_unlock_irqrestore(&imsic->ids_lock, flags);
+
+	imsic_ids_remote_sync();
+}
+
+static void imsic_irq_unmask(struct irq_data *d)
+{
+	unsigned long flags;
+
+	raw_spin_lock_irqsave(&imsic->ids_lock, flags);
+	bitmap_set(imsic->ids_enabled_bimap, d->hwirq, 1);
+	__imsic_id_enable(d->hwirq);
+	raw_spin_unlock_irqrestore(&imsic->ids_lock, flags);
+
+	imsic_ids_remote_sync();
+}
+
+static void imsic_irq_compose_msi_msg(struct irq_data *d,
+				      struct msi_msg *msg)
+{
+	phys_addr_t msi_addr;
+	unsigned int cpu;
+	int err;
+
+	cpu = imsic_id_get_target(d->hwirq);
+	if (WARN_ON(cpu == UINT_MAX))
+		return;
+
+	err = imsic_cpu_page_phys(cpu, 0, &msi_addr);
+	if (WARN_ON(err))
+		return;
+
+	msg->address_hi = upper_32_bits(msi_addr);
+	msg->address_lo = lower_32_bits(msi_addr);
+	msg->data = d->hwirq;
+}
+
+#ifdef CONFIG_SMP
+static int imsic_irq_set_affinity(struct irq_data *d,
+				  const struct cpumask *mask_val,
+				  bool force)
+{
+	unsigned int target_cpu;
+	int rc;
+
+	rc = imsic_get_cpu(mask_val, force, &target_cpu);
+	if (rc)
+		return rc;
+
+	imsic_id_set_target(d->hwirq, target_cpu);
+	irq_data_update_effective_affinity(d, cpumask_of(target_cpu));
+
+	return IRQ_SET_MASK_OK;
+}
+#endif
+
+static struct irq_chip imsic_irq_base_chip = {
+	.name			= "RISC-V IMSIC-BASE",
+	.irq_mask		= imsic_irq_mask,
+	.irq_unmask		= imsic_irq_unmask,
+#ifdef CONFIG_SMP
+	.irq_set_affinity	= imsic_irq_set_affinity,
+#endif
+	.irq_compose_msi_msg	= imsic_irq_compose_msi_msg,
+	.flags			= IRQCHIP_SKIP_SET_WAKE |
+				  IRQCHIP_MASK_ON_SUSPEND,
+};
+
+static int imsic_irq_domain_alloc(struct irq_domain *domain,
+				  unsigned int virq,
+				  unsigned int nr_irqs,
+				  void *args)
+{
+	int i, hwirq, err = 0;
+	unsigned int cpu;
+
+	err = imsic_get_cpu(&imsic->lmask, false, &cpu);
+	if (err)
+		return err;
+
+	hwirq = imsic_ids_alloc(get_count_order(nr_irqs));
+	if (hwirq < 0)
+		return hwirq;
+
+	for (i = 0; i < nr_irqs; i++) {
+		imsic_id_set_target(hwirq + i, cpu);
+		irq_domain_set_info(domain, virq + i, hwirq + i,
+				    &imsic_irq_base_chip, imsic,
+				    handle_simple_irq, NULL, NULL);
+		irq_set_noprobe(virq + i);
+		irq_set_affinity(virq + i, &imsic->lmask);
+		/*
+		 * IMSIC does not implement irq_disable() so Linux interrupt
+		 * subsystem will take a lazy approach for disabling an IMSIC
+		 * interrupt. This means IMSIC interrupts are left unmasked
+		 * upon system suspend and interrupts are not processed
+		 * immediately upon system wake up. To tackle this, we disable
+		 * the lazy approach for all IMSIC interrupts.
+		 */
+		irq_set_status_flags(virq + i, IRQ_DISABLE_UNLAZY);
+	}
+
+	return 0;
+}
+
+static void imsic_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);
+
+	imsic_ids_free(d->hwirq, get_count_order(nr_irqs));
+	irq_domain_free_irqs_parent(domain, virq, nr_irqs);
+}
+
+static const struct irq_domain_ops imsic_base_domain_ops = {
+	.alloc		= imsic_irq_domain_alloc,
+	.free		= imsic_irq_domain_free,
+};
+
+static struct irq_chip imsic_plat_irq_chip = {
+	.name			= "RISC-V IMSIC-PLAT",
+};
+
+static struct msi_domain_ops imsic_plat_domain_ops = {
+};
+
+static struct msi_domain_info imsic_plat_domain_info = {
+	.flags	= (MSI_FLAG_USE_DEF_DOM_OPS | MSI_FLAG_USE_DEF_CHIP_OPS),
+	.ops	= &imsic_plat_domain_ops,
+	.chip	= &imsic_plat_irq_chip,
+};
+
+static int __init imsic_irq_domains_init(struct fwnode_handle *fwnode)
+{
+	/* Create Base IRQ domain */
+	imsic->base_domain = irq_domain_create_tree(fwnode,
+					&imsic_base_domain_ops, imsic);
+	if (!imsic->base_domain) {
+		pr_err("Failed to create IMSIC base domain\n");
+		return -ENOMEM;
+	}
+	irq_domain_update_bus_token(imsic->base_domain, DOMAIN_BUS_NEXUS);
+
+	/* Create Platform MSI domain */
+	imsic->plat_domain = platform_msi_create_irq_domain(fwnode,
+						&imsic_plat_domain_info,
+						imsic->base_domain);
+	if (!imsic->plat_domain) {
+		pr_err("Failed to create IMSIC platform domain\n");
+		irq_domain_remove(imsic->base_domain);
+		return -ENOMEM;
+	}
+
+	return 0;
+}
+
+/*
+ * To handle an interrupt, we read the TOPEI CSR and write zero in one
+ * instruction. If TOPEI CSR is non-zero then we translate TOPEI.ID to
+ * Linux interrupt number and let Linux IRQ subsystem handle it.
+ */
+static void imsic_handle_irq(struct irq_desc *desc)
+{
+	struct irq_chip *chip = irq_desc_get_chip(desc);
+	irq_hw_number_t hwirq;
+	int err;
+
+	chained_irq_enter(chip, desc);
+
+	while ((hwirq = csr_swap(CSR_TOPEI, 0))) {
+		hwirq = hwirq >> TOPEI_ID_SHIFT;
+
+		if (hwirq == imsic->ipi_id) {
+#ifdef CONFIG_SMP
+			ipi_mux_process();
+#endif
+			continue;
+		}
+
+		err = generic_handle_domain_irq(imsic->base_domain, hwirq);
+		if (unlikely(err))
+			pr_warn_ratelimited(
+				"hwirq %lu mapping not found\n", hwirq);
+	}
+
+	chained_irq_exit(chip, desc);
+}
+
+static int imsic_starting_cpu(unsigned int cpu)
+{
+	/* Enable per-CPU parent interrupt */
+	enable_percpu_irq(imsic_parent_irq,
+			  irq_get_trigger_type(imsic_parent_irq));
+
+	/* Setup IPIs */
+	imsic_ipi_starting_cpu();
+
+	/*
+	 * Interrupts identities might have been enabled/disabled while
+	 * this CPU was not running so sync-up local enable/disable state.
+	 */
+	imsic_ids_local_sync();
+
+	/* Enable local interrupt delivery */
+	imsic_ids_local_delivery(true);
+
+	return 0;
+}
+
+static int imsic_dying_cpu(unsigned int cpu)
+{
+	/* Cleanup IPIs */
+	imsic_ipi_dying_cpu();
+
+	return 0;
+}
+
+static int __init imsic_get_parent_hartid(struct fwnode_handle *fwnode,
+					  u32 index, unsigned long *hartid)
+{
+	int rc;
+	struct fwnode_reference_args parent;
+
+	rc = fwnode_property_get_reference_args(fwnode,
+			"interrupts-extended", "#interrupt-cells",
+			0, index, &parent);
+	if (rc)
+		return rc;
+
+	/*
+	 * Skip interrupts other than external interrupts for
+	 * current privilege level.
+	 */
+	if (parent.args[0] != RV_IRQ_EXT)
+		return -EINVAL;
+
+	return riscv_fw_parent_hartid(parent.fwnode, hartid);
+}
+
+static int __init imsic_get_mmio_resource(struct fwnode_handle *fwnode,
+					  u32 index, struct resource *res)
+{
+	/*
+	 * Currently, only OF fwnode is support so extend this function
+	 * for other types of fwnode for ACPI support.
+	 */
+	if (!is_of_node(fwnode))
+		return -EINVAL;
+	return of_address_to_resource(to_of_node(fwnode), index, res);
+}
+
+static int __init imsic_init(struct fwnode_handle *fwnode)
+{
+	int rc, cpu;
+	phys_addr_t base_addr;
+	struct irq_domain *domain;
+	void __iomem **mmios_va = NULL;
+	struct resource res, *mmios = NULL;
+	struct imsic_local_config *local;
+	struct imsic_global_config *global;
+	unsigned long reloff, hartid;
+	u32 i, j, index, nr_parent_irqs, nr_handlers = 0, num_mmios = 0;
+
+	/*
+	 * Only one IMSIC instance allowed in a platform for clean
+	 * implementation of SMP IRQ affinity and per-CPU IPIs.
+	 *
+	 * This means on a multi-socket (or multi-die) platform we
+	 * will have multiple MMIO regions for one IMSIC instance.
+	 */
+	if (imsic) {
+		pr_err("%pfwP: already initialized hence ignoring\n",
+			fwnode);
+		return -ENODEV;
+	}
+
+	if (!riscv_isa_extension_available(NULL, SxAIA)) {
+		pr_err("%pfwP: AIA support not available\n", fwnode);
+		return -ENODEV;
+	}
+
+	imsic = kzalloc(sizeof(*imsic), GFP_KERNEL);
+	if (!imsic)
+		return -ENOMEM;
+	global = &imsic->global;
+
+	global->local = alloc_percpu(typeof(*(global->local)));
+	if (!global->local) {
+		rc = -ENOMEM;
+		goto out_free_priv;
+	}
+
+	/* Find number of parent interrupts */
+	nr_parent_irqs = 0;
+	while (!imsic_get_parent_hartid(fwnode, nr_parent_irqs, &hartid))
+		nr_parent_irqs++;
+	if (!nr_parent_irqs) {
+		pr_err("%pfwP: no parent irqs available\n", fwnode);
+		rc = -EINVAL;
+		goto out_free_local;
+	}
+
+	/* Find number of guest index bits in MSI address */
+	rc = fwnode_property_read_u32_array(fwnode, "riscv,guest-index-bits",
+					    &global->guest_index_bits, 1);
+	if (rc)
+		global->guest_index_bits = 0;
+	i = BITS_PER_LONG - IMSIC_MMIO_PAGE_SHIFT;
+	if (i < global->guest_index_bits) {
+		pr_err("%pfwP: guest index bits too big\n", fwnode);
+		rc = -EINVAL;
+		goto out_free_local;
+	}
+
+	/* Find number of HART index bits */
+	rc = fwnode_property_read_u32_array(fwnode, "riscv,hart-index-bits",
+					    &global->hart_index_bits, 1);
+	if (rc) {
+		/* Assume default value */
+		global->hart_index_bits = __fls(nr_parent_irqs);
+		if (BIT(global->hart_index_bits) < nr_parent_irqs)
+			global->hart_index_bits++;
+	}
+	i = BITS_PER_LONG - IMSIC_MMIO_PAGE_SHIFT - global->guest_index_bits;
+	if (i < global->hart_index_bits) {
+		pr_err("%pfwP: HART index bits too big\n", fwnode);
+		rc = -EINVAL;
+		goto out_free_local;
+	}
+
+	/* Find number of group index bits */
+	rc = fwnode_property_read_u32_array(fwnode, "riscv,group-index-bits",
+					    &global->group_index_bits, 1);
+	if (rc)
+		global->group_index_bits = 0;
+	i = BITS_PER_LONG - IMSIC_MMIO_PAGE_SHIFT -
+	    global->guest_index_bits - global->hart_index_bits;
+	if (i < global->group_index_bits) {
+		pr_err("%pfwP: group index bits too big\n", fwnode);
+		rc = -EINVAL;
+		goto out_free_local;
+	}
+
+	/*
+	 * Find first bit position of group index.
+	 * If not specified assumed the default APLIC-IMSIC configuration.
+	 */
+	rc = fwnode_property_read_u32_array(fwnode, "riscv,group-index-shift",
+					    &global->group_index_shift, 1);
+	if (rc)
+		global->group_index_shift = IMSIC_MMIO_PAGE_SHIFT * 2;
+	i = global->group_index_bits + global->group_index_shift - 1;
+	if (i >= BITS_PER_LONG) {
+		pr_err("%pfwP: group index shift too big\n", fwnode);
+		rc = -EINVAL;
+		goto out_free_local;
+	}
+
+	/* Find number of interrupt identities */
+	rc = fwnode_property_read_u32_array(fwnode, "riscv,num-ids",
+					    &global->nr_ids, 1);
+	if (rc) {
+		pr_err("%pfwP: number of interrupt identities not found\n",
+			fwnode);
+		goto out_free_local;
+	}
+	if ((global->nr_ids < IMSIC_MIN_ID) ||
+	    (global->nr_ids >= IMSIC_MAX_ID) ||
+	    ((global->nr_ids & IMSIC_MIN_ID) != IMSIC_MIN_ID)) {
+		pr_err("%pfwP: invalid number of interrupt identities\n",
+			fwnode);
+		rc = -EINVAL;
+		goto out_free_local;
+	}
+
+	/* Find number of guest interrupt identities */
+	if (fwnode_property_read_u32_array(fwnode, "riscv,num-guest-ids",
+					   &global->nr_guest_ids, 1))
+		global->nr_guest_ids = global->nr_ids;
+	if ((global->nr_guest_ids < IMSIC_MIN_ID) ||
+	    (global->nr_guest_ids >= IMSIC_MAX_ID) ||
+	    ((global->nr_guest_ids & IMSIC_MIN_ID) != IMSIC_MIN_ID)) {
+		pr_err("%pfwP: invalid number of guest interrupt identities\n",
+			fwnode);
+		rc = -EINVAL;
+		goto out_free_local;
+	}
+
+	/* Compute base address */
+	rc = imsic_get_mmio_resource(fwnode, 0, &res);
+	if (rc) {
+		pr_err("%pfwP: first MMIO resource not found\n", fwnode);
+		rc = -EINVAL;
+		goto out_free_local;
+	}
+	global->base_addr = res.start;
+	global->base_addr &= ~(BIT(global->guest_index_bits +
+				   global->hart_index_bits +
+				   IMSIC_MMIO_PAGE_SHIFT) - 1);
+	global->base_addr &= ~((BIT(global->group_index_bits) - 1) <<
+			       global->group_index_shift);
+
+	/* Find number of MMIO register sets */
+	while (!imsic_get_mmio_resource(fwnode, num_mmios, &res))
+		num_mmios++;
+
+	/* Allocate MMIO resource array */
+	mmios = kcalloc(num_mmios, sizeof(*mmios), GFP_KERNEL);
+	if (!mmios) {
+		rc = -ENOMEM;
+		goto out_free_local;
+	}
+
+	/* Allocate MMIO virtual address array */
+	mmios_va = kcalloc(num_mmios, sizeof(*mmios_va), GFP_KERNEL);
+	if (!mmios_va) {
+		rc = -ENOMEM;
+		goto out_iounmap;
+	}
+
+	/* Parse and map MMIO register sets */
+	for (i = 0; i < num_mmios; i++) {
+		rc = imsic_get_mmio_resource(fwnode, i, &mmios[i]);
+		if (rc) {
+			pr_err("%pfwP: unable to parse MMIO regset %d\n",
+				fwnode, i);
+			goto out_iounmap;
+		}
+
+		base_addr = mmios[i].start;
+		base_addr &= ~(BIT(global->guest_index_bits +
+				   global->hart_index_bits +
+				   IMSIC_MMIO_PAGE_SHIFT) - 1);
+		base_addr &= ~((BIT(global->group_index_bits) - 1) <<
+			       global->group_index_shift);
+		if (base_addr != global->base_addr) {
+			rc = -EINVAL;
+			pr_err("%pfwP: address mismatch for regset %d\n",
+				fwnode, i);
+			goto out_iounmap;
+		}
+
+		mmios_va[i] = ioremap(mmios[i].start, resource_size(&mmios[i]));
+		if (!mmios_va[i]) {
+			rc = -EIO;
+			pr_err("%pfwP: unable to map MMIO regset %d\n",
+				fwnode, i);
+			goto out_iounmap;
+		}
+	}
+
+	/* Initialize interrupt identity management */
+	rc = imsic_ids_init();
+	if (rc) {
+		pr_err("%pfwP: failed to initialize interrupt management\n",
+		       fwnode);
+		goto out_iounmap;
+	}
+
+	/* Configure handlers for target CPUs */
+	for (i = 0; i < nr_parent_irqs; i++) {
+		rc = imsic_get_parent_hartid(fwnode, i, &hartid);
+		if (rc) {
+			pr_warn("%pfwP: hart ID for parent irq%d not found\n",
+				fwnode, i);
+			continue;
+		}
+
+		cpu = riscv_hartid_to_cpuid(hartid);
+		if (cpu < 0) {
+			pr_warn("%pfwP: invalid cpuid for parent irq%d\n",
+				fwnode, i);
+			continue;
+		}
+
+		/* Find MMIO location of MSI page */
+		index = num_mmios;
+		reloff = i * BIT(global->guest_index_bits) *
+			 IMSIC_MMIO_PAGE_SZ;
+		for (j = 0; num_mmios; j++) {
+			if (reloff < resource_size(&mmios[j])) {
+				index = j;
+				break;
+			}
+
+			/*
+			 * MMIO region size may not be aligned to
+			 * BIT(global->guest_index_bits) * IMSIC_MMIO_PAGE_SZ
+			 * if holes are present.
+			 */
+			reloff -= ALIGN(resource_size(&mmios[j]),
+			BIT(global->guest_index_bits) * IMSIC_MMIO_PAGE_SZ);
+		}
+		if (index >= num_mmios) {
+			pr_warn("%pfwP: MMIO not found for parent irq%d\n",
+				fwnode, i);
+			continue;
+		}
+
+		cpumask_set_cpu(cpu, &imsic->lmask);
+
+		local = per_cpu_ptr(global->local, cpu);
+		local->msi_pa = mmios[index].start + reloff;
+		local->msi_va = mmios_va[index] + reloff;
+
+		nr_handlers++;
+	}
+
+	/* If no CPU handlers found then can't take interrupts */
+	if (!nr_handlers) {
+		pr_err("%pfwP: No CPU handlers found\n", fwnode);
+		rc = -ENODEV;
+		goto out_ids_cleanup;
+	}
+
+	/* Find parent domain and register chained handler */
+	domain = irq_find_matching_fwnode(riscv_get_intc_hwnode(),
+					  DOMAIN_BUS_ANY);
+	if (!domain) {
+		pr_err("%pfwP: Failed to find INTC domain\n", fwnode);
+		rc = -ENOENT;
+		goto out_ids_cleanup;
+	}
+	imsic_parent_irq = irq_create_mapping(domain, RV_IRQ_EXT);
+	if (!imsic_parent_irq) {
+		pr_err("%pfwP: Failed to create INTC mapping\n", fwnode);
+		rc = -ENOENT;
+		goto out_ids_cleanup;
+	}
+	irq_set_chained_handler(imsic_parent_irq, imsic_handle_irq);
+
+	/* Initialize IPI domain */
+	rc = imsic_ipi_domain_init();
+	if (rc) {
+		pr_err("%pfwP: Failed to initialize IPI domain\n", fwnode);
+		goto out_ids_cleanup;
+	}
+
+	/* Initialize IRQ and MSI domains */
+	rc = imsic_irq_domains_init(fwnode);
+	if (rc) {
+		pr_err("%pfwP: Failed to initialize IRQ and MSI domains\n",
+		       fwnode);
+		goto out_ipi_domain_cleanup;
+	}
+
+	/*
+	 * Setup cpuhp state (must be done after setting imsic_parent_irq)
+	 *
+	 * Don't disable per-CPU IMSIC file when CPU goes offline
+	 * because this affects IPI and the masking/unmasking of
+	 * virtual IPIs is done via generic IPI-Mux
+	 */
+	cpuhp_setup_state(CPUHP_AP_ONLINE_DYN,
+			  "irqchip/riscv/imsic:starting",
+			  imsic_starting_cpu, imsic_dying_cpu);
+
+	/* We don't need MMIO arrays anymore so let's free-up */
+	kfree(mmios_va);
+	kfree(mmios);
+
+	pr_info("%pfwP:  hart-index-bits: %d,  guest-index-bits: %d\n",
+		fwnode, global->hart_index_bits, global->guest_index_bits);
+	pr_info("%pfwP: group-index-bits: %d, group-index-shift: %d\n",
+		fwnode, global->group_index_bits, global->group_index_shift);
+	pr_info("%pfwP: mapped %d interrupts for %d CPUs at %pa\n",
+		fwnode, global->nr_ids, nr_handlers, &global->base_addr);
+	if (imsic->ipi_id)
+		pr_info("%pfwP: providing IPIs using interrupt %d\n",
+			fwnode, imsic->ipi_id);
+
+	return 0;
+
+out_ipi_domain_cleanup:
+	imsic_ipi_domain_cleanup();
+out_ids_cleanup:
+	imsic_ids_cleanup();
+out_iounmap:
+	for (i = 0; i < num_mmios; i++) {
+		if (mmios_va[i])
+			iounmap(mmios_va[i]);
+	}
+	kfree(mmios_va);
+	kfree(mmios);
+out_free_local:
+	free_percpu(imsic->global.local);
+out_free_priv:
+	kfree(imsic);
+	imsic = NULL;
+	return rc;
+}
+
+static int __init imsic_dt_init(struct device_node *node,
+				struct device_node *parent)
+{
+	return imsic_init(&node->fwnode);
+}
+IRQCHIP_DECLARE(riscv_imsic, "riscv,imsics", imsic_dt_init);
diff --git a/include/linux/irqchip/riscv-imsic.h b/include/linux/irqchip/riscv-imsic.h
new file mode 100644
index 000000000000..1f6fc9a57218
--- /dev/null
+++ b/include/linux/irqchip/riscv-imsic.h
@@ -0,0 +1,86 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2021 Western Digital Corporation or its affiliates.
+ * Copyright (C) 2022 Ventana Micro Systems Inc.
+ */
+#ifndef __LINUX_IRQCHIP_RISCV_IMSIC_H
+#define __LINUX_IRQCHIP_RISCV_IMSIC_H
+
+#include <linux/types.h>
+#include <asm/csr.h>
+
+#define IMSIC_MMIO_PAGE_SHIFT		12
+#define IMSIC_MMIO_PAGE_SZ		(1UL << IMSIC_MMIO_PAGE_SHIFT)
+#define IMSIC_MMIO_PAGE_LE		0x00
+#define IMSIC_MMIO_PAGE_BE		0x04
+
+#define IMSIC_MIN_ID			63
+#define IMSIC_MAX_ID			2048
+
+#define IMSIC_EIDELIVERY		0x70
+
+#define IMSIC_EITHRESHOLD		0x72
+
+#define IMSIC_EIP0			0x80
+#define IMSIC_EIP63			0xbf
+#define IMSIC_EIPx_BITS			32
+
+#define IMSIC_EIE0			0xc0
+#define IMSIC_EIE63			0xff
+#define IMSIC_EIEx_BITS			32
+
+#define IMSIC_FIRST			IMSIC_EIDELIVERY
+#define IMSIC_LAST			IMSIC_EIE63
+
+#define IMSIC_MMIO_SETIPNUM_LE		0x00
+#define IMSIC_MMIO_SETIPNUM_BE		0x04
+
+struct imsic_local_config {
+	phys_addr_t msi_pa;
+	void __iomem *msi_va;
+};
+
+struct imsic_global_config {
+	/*
+	 * MSI Target Address Scheme
+	 *
+	 * XLEN-1                                                12     0
+	 * |                                                     |     |
+	 * -------------------------------------------------------------
+	 * |xxxxxx|Group Index|xxxxxxxxxxx|HART Index|Guest Index|  0  |
+	 * -------------------------------------------------------------
+	 */
+
+	/* Bits representing Guest index, HART index, and Group index */
+	u32 guest_index_bits;
+	u32 hart_index_bits;
+	u32 group_index_bits;
+	u32 group_index_shift;
+
+	/* Global base address matching all target MSI addresses */
+	phys_addr_t base_addr;
+
+	/* Number of interrupt identities */
+	u32 nr_ids;
+
+	/* Number of guest interrupt identities */
+	u32 nr_guest_ids;
+
+	/* Per-CPU IMSIC addresses */
+	struct imsic_local_config __percpu *local;
+};
+
+#ifdef CONFIG_RISCV_IMSIC
+
+extern const struct imsic_global_config *imsic_get_global_config(void);
+
+#else
+
+static inline const struct imsic_global_config *imsic_get_global_config(void)
+{
+	return NULL;
+}
+
+#endif
+
+#endif
-- 
2.34.1