[PATCH v2 15/25] irqchip/apple-aic: Add support for the Apple Interrupt Controller

[Hector Martin]

This is the root interrupt controller used on Apple ARM SoCs such as the
M1. This irqchip driver performs multiple functions:

* Discriminates between IRQs and FIQs

* Drives the AIC peripheral itself (which handles IRQs)

* Dispatches FIQs to downstream hard-wired clients (currently the ARM
  timer).

This patch introduces basic UP irqchip support, without SMP/IPI support.

Signed-off-by: Hector Martin <marcan@xxxxxxxxx>
---
 MAINTAINERS                     |   2 +
 drivers/irqchip/Kconfig         |  10 +
 drivers/irqchip/Makefile        |   1 +
 drivers/irqchip/irq-apple-aic.c | 647 ++++++++++++++++++++++++++++++++
 include/linux/cpuhotplug.h      |   1 +
 5 files changed, 661 insertions(+)
 create mode 100644 drivers/irqchip/irq-apple-aic.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 9fe723033e63..a8f258fbb5f1 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -1636,6 +1636,8 @@ T:	git https://github.com/AsahiLinux/linux.git
 F:	Documentation/devicetree/bindings/arm/apple.yaml
 F:	Documentation/devicetree/bindings/interrupt-controller/apple,aic.yaml
 F:	arch/arm64/include/asm/sysreg_apple.h
+F:	drivers/irqchip/irq-apple-aic.c
+F:	include/dt-bindings/interrupt-controller/apple-aic.h
 
 ARM/ARTPEC MACHINE SUPPORT
 M:	Jesper Nilsson <jesper.nilsson@xxxxxxxx>
diff --git a/drivers/irqchip/Kconfig b/drivers/irqchip/Kconfig
index b147f22a78f4..fca080640c1a 100644
--- a/drivers/irqchip/Kconfig
+++ b/drivers/irqchip/Kconfig
@@ -590,4 +590,14 @@ config MST_IRQ
 	help
 	  Support MStar Interrupt Controller.
 
+config APPLE_AIC
+	bool "Apple Interrupt Controller (AIC)"
+	depends on ARM64
+	default ARCH_APPLE
+	select IRQ_DOMAIN
+	select IRQ_DOMAIN_HIERARCHY
+	help
+	  Support for the Apple Interrupt Controller found on Apple Silicon SoCs,
+	  such as the M1.
+
 endmenu
diff --git a/drivers/irqchip/Makefile b/drivers/irqchip/Makefile
index 0ac93bfaec61..0e2ba7c2dce7 100644
--- a/drivers/irqchip/Makefile
+++ b/drivers/irqchip/Makefile
@@ -113,3 +113,4 @@ obj-$(CONFIG_LOONGSON_PCH_PIC)		+= irq-loongson-pch-pic.o
 obj-$(CONFIG_LOONGSON_PCH_MSI)		+= irq-loongson-pch-msi.o
 obj-$(CONFIG_MST_IRQ)			+= irq-mst-intc.o
 obj-$(CONFIG_SL28CPLD_INTC)		+= irq-sl28cpld.o
+obj-$(CONFIG_APPLE_AIC)			+= irq-apple-aic.o
diff --git a/drivers/irqchip/irq-apple-aic.c b/drivers/irqchip/irq-apple-aic.c
new file mode 100644
index 000000000000..604dbb8fd898
--- /dev/null
+++ b/drivers/irqchip/irq-apple-aic.c
@@ -0,0 +1,647 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright The Asahi Linux Contributors
+ *
+ * Based on irq-lpc32xx:
+ *   Copyright 2015-2016 Vladimir Zapolskiy <vz@xxxxxxxxx>
+ * Based on irq-bcm2836:
+ *   Copyright 2015 Broadcom
+ */
+
+/*
+ * AIC is a fairly simple interrupt controller with the following features:
+ *
+ * - 896 level-triggered hardware IRQs
+ *   - Single mask bit per IRQ
+ *   - Per-IRQ affinity setting
+ *   - Automatic masking on event delivery (auto-ack)
+ *   - Software triggering (ORed with hw line)
+ * - 2 per-CPU IPIs (meant as "self" and "other", but they are interchangeable if not symmetric)
+ * - Automatic prioritization (single event/ack register per CPU, lower IRQs = higher priority)
+ * - Automatic masking on ack
+ * - Default "this CPU" register view and explicit per-CPU views
+ *
+ * In addition, this driver also handles FIQs, as these are routed to the same IRQ vector. These
+ * are used for Fast IPIs (TODO), the ARMv8 timer IRQs, and performance counters (TODO).
+ *
+ * Implementation notes:
+ *
+ * - This driver creates two IRQ domains, one for HW IRQs and internal FIQs, and one for IPIs
+ * - Since Linux needs more than 2 IPIs, we implement a software IRQ controller and funnel all IPIs
+ *   into one per-CPU IPI (the second "self" IPI is unused).
+ * - FIQ hwirq numbers are assigned after true hwirqs, and are per-cpu
+ * - DT bindings use 3-cell form (like GIC):
+ *   - <0 nr flags> - hwirq #nr
+ *   - <1 nr flags> - FIQ #nr
+ *     - nr=0  Physical HV timer
+ *     - nr=1  Virtual HV timer
+ *     - nr=2  Physical guest timer
+ *     - nr=3  Virtual guest timer
+ *
+ */
+
+#define pr_fmt(fmt) "%s: " fmt, __func__
+
+#include <linux/bits.h>
+#include <linux/bitfield.h>
+#include <linux/cpuhotplug.h>
+#include <linux/io.h>
+#include <linux/irqchip.h>
+#include <linux/irqchip/arm-gic-v3.h>
+#include <linux/irqdomain.h>
+#include <linux/of_address.h>
+#include <linux/slab.h>
+#include <asm/exception.h>
+#include <asm/sysreg.h>
+#include <asm/sysreg_apple.h>
+
+#include <dt-bindings/interrupt-controller/apple-aic.h>
+
+#define AIC_INFO		0x0004
+#define AIC_INFO_NR_HW		GENMASK(15, 0)
+
+#define AIC_CONFIG		0x0010
+
+#define AIC_WHOAMI		0x2000
+#define AIC_EVENT		0x2004
+#define AIC_EVENT_TYPE		GENMASK(31, 16)
+#define AIC_EVENT_NUM		GENMASK(15, 0)
+
+#define AIC_EVENT_TYPE_HW	1
+#define AIC_EVENT_TYPE_IPI	4
+#define AIC_EVENT_IPI_OTHER	1
+#define AIC_EVENT_IPI_SELF	2
+
+#define AIC_IPI_SEND		0x2008
+#define AIC_IPI_ACK		0x200c
+#define AIC_IPI_MASK_SET	0x2024
+#define AIC_IPI_MASK_CLR	0x2028
+
+#define AIC_IPI_SEND_CPU(cpu)	BIT(cpu)
+
+#define AIC_IPI_OTHER		BIT(0)
+#define AIC_IPI_SELF		BIT(31)
+
+#define AIC_TARGET_CPU		0x3000
+#define AIC_SW_SET		0x4000
+#define AIC_SW_CLR		0x4080
+#define AIC_MASK_SET		0x4100
+#define AIC_MASK_CLR		0x4180
+
+#define AIC_CPU_IPI_SET(cpu)	(0x5008 + ((cpu) << 7))
+#define AIC_CPU_IPI_CLR(cpu)	(0x500c + ((cpu) << 7))
+#define AIC_CPU_IPI_MASK_SET(cpu) (0x5024 + ((cpu) << 7))
+#define AIC_CPU_IPI_MASK_CLR(cpu) (0x5028 + ((cpu) << 7))
+
+#define MASK_REG(x)		(4 * ((x) >> 5))
+#define MASK_BIT(x)		BIT((x) & 0x1f)
+
+#define AIC_NR_FIQ		4
+#define AIC_NR_SWIPI		32
+
+/*
+ * Max 31 bits in IPI SEND register (top bit is self).
+ * >=32-core chips will need code changes anyway.
+ */
+#define AIC_MAX_CPUS		31
+
+struct aic_irq_chip {
+	void __iomem *base;
+	struct irq_domain *hw_domain;
+	struct irq_domain *ipi_domain;
+	int nr_hw;
+	int ipi_hwirq;
+};
+
+static atomic_t aic_vipi_flag[AIC_MAX_CPUS];
+static atomic_t aic_vipi_mask[AIC_MAX_CPUS];
+
+static struct aic_irq_chip *aic_irqc;
+
+static void aic_handle_ipi(struct pt_regs *regs);
+
+static u32 aic_ic_read(struct aic_irq_chip *ic, u32 reg)
+{
+	return readl_relaxed(ic->base + reg);
+}
+
+static void aic_ic_write(struct aic_irq_chip *ic, u32 reg, u32 val)
+{
+	writel_relaxed(val, ic->base + reg);
+}
+
+/*
+ * IRQ irqchip
+ */
+
+static void aic_irq_mask(struct irq_data *d)
+{
+	struct aic_irq_chip *ic = irq_data_get_irq_chip_data(d);
+
+	aic_ic_write(ic, AIC_MASK_SET + MASK_REG(d->hwirq),
+		     MASK_BIT(d->hwirq));
+}
+
+static void aic_irq_unmask(struct irq_data *d)
+{
+	struct aic_irq_chip *ic = irq_data_get_irq_chip_data(d);
+
+	aic_ic_write(ic, AIC_MASK_CLR + MASK_REG(d->hwirq),
+		     MASK_BIT(d->hwirq));
+}
+
+static void aic_irq_eoi(struct irq_data *d)
+{
+	/*
+	 * Reading the interrupt reason automatically acknowledges and masks
+	 * the IRQ, so we just unmask it here if needed.
+	 */
+	if (!irqd_irq_disabled(d) && !irqd_irq_masked(d))
+		aic_irq_unmask(d);
+}
+
+static void aic_handle_irq(struct pt_regs *regs)
+{
+	struct aic_irq_chip *ic = aic_irqc;
+	u32 event, type, irq;
+
+	do {
+		/*
+		 * We cannot use a relaxed read here, as DMA needs to be
+		 * ordered with respect to the IRQ firing.
+		 */
+		event = readl(ic->base + AIC_EVENT);
+		type = FIELD_GET(AIC_EVENT_TYPE, event);
+		irq = FIELD_GET(AIC_EVENT_NUM, event);
+
+		if (type == AIC_EVENT_TYPE_HW)
+			handle_domain_irq(aic_irqc->hw_domain, irq, regs);
+		else if (type == AIC_EVENT_TYPE_IPI && irq == 1)
+			aic_handle_ipi(regs);
+		else if (event != 0)
+			pr_err("Unknown IRQ event %d, %d\n", type, irq);
+	} while (event);
+
+	/*
+	 * vGIC maintenance interrupts end up here too, so we need to check
+	 * for them separately. Just report and disable vGIC for now, until
+	 * we implement this properly.
+	 */
+	if ((read_sysreg_s(SYS_ICH_HCR_EL2) & ICH_HCR_EN) &&
+		read_sysreg_s(SYS_ICH_MISR_EL2) != 0) {
+		pr_err("vGIC IRQ fired, disabling.\n");
+		sysreg_clear_set_s(SYS_ICH_HCR_EL2, ICH_HCR_EN, 0);
+	}
+}
+
+static int aic_irq_set_affinity(struct irq_data *d,
+				const struct cpumask *mask_val, bool force)
+{
+	irq_hw_number_t hwirq = irqd_to_hwirq(d);
+	struct aic_irq_chip *ic = irq_data_get_irq_chip_data(d);
+	int cpu;
+
+	if (hwirq > ic->nr_hw)
+		return -EINVAL;
+
+	if (force)
+		cpu = cpumask_first(mask_val);
+	else
+		cpu = cpumask_any_and(mask_val, cpu_online_mask);
+
+	aic_ic_write(ic, AIC_TARGET_CPU + hwirq * 4, BIT(cpu));
+	irq_data_update_effective_affinity(d, cpumask_of(cpu));
+
+	return IRQ_SET_MASK_OK;
+}
+
+static struct irq_chip aic_chip = {
+	.name = "AIC",
+	.irq_mask = aic_irq_mask,
+	.irq_unmask = aic_irq_unmask,
+	.irq_eoi = aic_irq_eoi,
+	.irq_set_affinity = aic_irq_set_affinity,
+};
+
+/*
+ * FIQ irqchip
+ */
+
+static void aic_fiq_mask(struct irq_data *d)
+{
+	/* Only the guest timers have real mask bits, unfortunately. */
+	switch (d->hwirq) {
+	case AIC_TMR_GUEST_PHYS:
+		sysreg_clear_set_s(SYS_APL_VM_TMR_MASK,
+					VM_TMR_MASK_P, 0);
+		break;
+	case AIC_TMR_GUEST_VIRT:
+		sysreg_clear_set_s(SYS_APL_VM_TMR_MASK,
+					VM_TMR_MASK_V, 0);
+		break;
+	}
+}
+
+static void aic_fiq_unmask(struct irq_data *d)
+{
+	switch (d->hwirq) {
+	case AIC_TMR_GUEST_PHYS:
+		sysreg_clear_set_s(SYS_APL_VM_TMR_MASK,
+					0, VM_TMR_MASK_P);
+		break;
+	case AIC_TMR_GUEST_VIRT:
+		sysreg_clear_set_s(SYS_APL_VM_TMR_MASK,
+					0, VM_TMR_MASK_V);
+		break;
+	}
+}
+
+static void aic_fiq_eoi(struct irq_data *d)
+{
+	/* We mask to ack (where we can), so we need to unmask at EOI. */
+	if (!irqd_irq_disabled(d) && !irqd_irq_masked(d))
+		aic_fiq_unmask(d);
+}
+
+#define TIMER_FIRING(x)                                                        \
+	(((x) & (ARCH_TIMER_CTRL_ENABLE | ARCH_TIMER_CTRL_IT_MASK |            \
+		 ARCH_TIMER_CTRL_IT_STAT)) ==                                  \
+	 (ARCH_TIMER_CTRL_ENABLE | ARCH_TIMER_CTRL_IT_STAT))
+
+static void aic_handle_fiq(struct pt_regs *regs)
+{
+	/*
+	 * It would be really if we had a system register that lets us get
+	 * the FIQ source state without having to peek down into sources...
+	 * but such a register does not seem to exist.
+	 *
+	 * So, we have these potential sources to test for:
+	 *  - Fast IPIs (not yet used)
+	 *  - The 4 timers (CNTP, CNTV for each of HV and guest)
+	 *  - Per-core PMCs (not yet supported)
+	 *  - Per-cluster uncore PMCs (not yet supported)
+	 *
+	 * Since not dealing with any of these results in a FIQ storm,
+	 * we check for everything here, even things we don't support yet.
+	 */
+
+	if (read_sysreg_s(SYS_APL_IPI_SR) & IPI_SR_PENDING) {
+		pr_warn("Fast IPI fired. Acking.\n");
+		write_sysreg_s(IPI_SR_PENDING, SYS_APL_IPI_SR);
+	}
+
+	if (TIMER_FIRING(read_sysreg(cntp_ctl_el0)))
+		handle_domain_irq(aic_irqc->hw_domain,
+				  aic_irqc->nr_hw + AIC_TMR_HV_PHYS, regs);
+
+	if (TIMER_FIRING(read_sysreg(cntv_ctl_el0)))
+		handle_domain_irq(aic_irqc->hw_domain,
+				  aic_irqc->nr_hw + AIC_TMR_HV_VIRT, regs);
+
+	if (TIMER_FIRING(read_sysreg_s(SYS_CNTP_CTL_EL02)))
+		handle_domain_irq(aic_irqc->hw_domain,
+				  aic_irqc->nr_hw + AIC_TMR_GUEST_PHYS, regs);
+
+	if (TIMER_FIRING(read_sysreg_s(SYS_CNTV_CTL_EL02)))
+		handle_domain_irq(aic_irqc->hw_domain,
+				  aic_irqc->nr_hw + AIC_TMR_GUEST_VIRT, regs);
+
+	if ((read_sysreg_s(SYS_APL_PMCR0) & (PMCR0_IMODE | PMCR0_IACT))
+			== (FIELD_PREP(PMCR0_IMODE, PMCR0_IMODE_FIQ) | PMCR0_IACT)) {
+		/*
+		 * Not supported yet, let's figure out how to handle this when
+		 * we implement these proprietary performance counters. For now,
+		 * just mask it and move on.
+		 */
+		pr_warn("PMC FIQ fired. Masking.\n");
+		sysreg_clear_set_s(SYS_APL_PMCR0, PMCR0_IMODE | PMCR0_IACT,
+				   FIELD_PREP(PMCR0_IMODE, PMCR0_IMODE_OFF));
+	}
+
+	if (FIELD_GET(UPMCR0_IMODE, read_sysreg_s(SYS_APL_UPMCR0)) == UPMCR0_IMODE_FIQ &&
+			(read_sysreg_s(SYS_APL_UPMSR) & UPMSR_IACT)) {
+		/* Same story with uncore PMCs */
+		pr_warn("Uncore PMC FIQ fired. Masking.\n");
+		sysreg_clear_set_s(SYS_APL_UPMCR0, UPMCR0_IMODE,
+				   FIELD_PREP(UPMCR0_IMODE, UPMCR0_IMODE_OFF));
+	}
+}
+
+static struct irq_chip fiq_chip = {
+	.name = "AIC-FIQ",
+	.irq_mask = aic_fiq_mask,
+	.irq_unmask = aic_fiq_unmask,
+	.irq_ack = aic_fiq_mask,
+	.irq_eoi = aic_fiq_eoi,
+};
+
+/*
+ * Main IRQ domain
+ */
+
+static void __exception_irq_entry aic_handle_irq_or_fiq(struct pt_regs *regs)
+{
+	u64 isr = read_sysreg(isr_el1);
+
+	if (isr & PSR_F_BIT)
+		aic_handle_fiq(regs);
+
+	if (isr & PSR_I_BIT)
+		aic_handle_irq(regs);
+}
+
+static int aic_irq_domain_map(struct irq_domain *id, unsigned int irq,
+			      irq_hw_number_t hw)
+{
+	struct aic_irq_chip *ic = id->host_data;
+
+	irq_set_chip_data(irq, ic);
+	if (hw < ic->nr_hw) {
+		irq_set_chip_and_handler(irq, &aic_chip, handle_fasteoi_irq);
+	} else {
+		irq_set_percpu_devid(irq);
+		irq_set_chip_and_handler(irq, &fiq_chip,
+					 handle_percpu_devid_irq);
+	}
+
+	irq_set_status_flags(irq, IRQ_LEVEL);
+	irq_set_noprobe(irq);
+
+	return 0;
+}
+
+static void aic_irq_domain_unmap(struct irq_domain *id, unsigned int irq)
+{
+	irq_set_chip_and_handler(irq, NULL, NULL);
+}
+
+static int aic_irq_domain_xlate(struct irq_domain *id,
+				struct device_node *ctrlr, const u32 *intspec,
+				unsigned int intsize,
+				irq_hw_number_t *out_hwirq,
+				unsigned int *out_type)
+{
+	struct aic_irq_chip *ic = id->host_data;
+
+	if (intsize != 3)
+		return -EINVAL;
+
+	if (intspec[0] == AIC_IRQ && intspec[1] < ic->nr_hw)
+		*out_hwirq = intspec[1];
+	else if (intspec[0] == AIC_FIQ && intspec[1] < AIC_NR_FIQ)
+		*out_hwirq = ic->nr_hw + intspec[1];
+	else
+		return -EINVAL;
+
+	*out_type = intspec[2] & IRQ_TYPE_SENSE_MASK;
+
+	return 0;
+}
+
+static const struct irq_domain_ops aic_irq_domain_ops = {
+	.map = aic_irq_domain_map,
+	.unmap = aic_irq_domain_unmap,
+	.xlate = aic_irq_domain_xlate,
+};
+
+/*
+ * IPI irqchip
+ */
+
+static void aic_ipi_mask(struct irq_data *d)
+{
+	struct aic_irq_chip *ic = irq_data_get_irq_chip_data(d);
+	u32 irq_bit = BIT(irqd_to_hwirq(d));
+	int this_cpu = smp_processor_id();
+
+	atomic_and(~irq_bit, &aic_vipi_mask[this_cpu]);
+
+	if (!atomic_read(&aic_vipi_mask[this_cpu]))
+		aic_ic_write(ic, AIC_IPI_MASK_SET, AIC_IPI_OTHER);
+}
+
+static void aic_ipi_unmask(struct irq_data *d)
+{
+	struct aic_irq_chip *ic = irq_data_get_irq_chip_data(d);
+	u32 irq_bit = BIT(irqd_to_hwirq(d));
+	int this_cpu = smp_processor_id();
+
+	atomic_or(irq_bit, &aic_vipi_mask[this_cpu]);
+
+	aic_ic_write(ic, AIC_IPI_MASK_CLR, AIC_IPI_OTHER);
+}
+
+static void aic_ipi_send_mask(struct irq_data *d, const struct cpumask *mask)
+{
+	struct aic_irq_chip *ic = irq_data_get_irq_chip_data(d);
+	u32 irq_bit = BIT(irqd_to_hwirq(d));
+	u32 send = 0;
+	int cpu;
+
+	/*
+	 * Ensure that stores to normal memory are visible to the
+	 * other CPUs before issuing the IPI. This needs to happen
+	 * before setting any vIPI flag bits, since that can race the
+	 * atomic_xchg below.
+	 */
+	wmb();
+
+	for_each_cpu(cpu, mask) {
+		if (atomic_read(&aic_vipi_mask[cpu]) & irq_bit) {
+			atomic_or(irq_bit, &aic_vipi_flag[cpu]);
+			send |= AIC_IPI_SEND_CPU(cpu);
+		}
+	}
+
+	if (send) {
+		/*
+		 * Ensure that the vIPI flag writes complete before issuing
+		 * the physical IPI.
+		 */
+		wmb();
+		aic_ic_write(ic, AIC_IPI_SEND, send);
+	}
+}
+
+static struct irq_chip ipi_chip = {
+	.name = "AIC-IPI",
+	.irq_mask = aic_ipi_mask,
+	.irq_unmask = aic_ipi_unmask,
+	.ipi_send_mask = aic_ipi_send_mask,
+};
+
+/*
+ * IPI IRQ domain
+ */
+
+static void aic_handle_ipi(struct pt_regs *regs)
+{
+	int this_cpu = smp_processor_id();
+	int i;
+	unsigned long firing;
+
+	aic_ic_write(aic_irqc, AIC_IPI_ACK, AIC_IPI_OTHER);
+
+	/*
+	 * Ensure that we've received and acked the IPI before we load the vIPI
+	 * flags. This pairs with the second wmb() above.
+	 */
+	mb();
+
+	firing = atomic_xchg(&aic_vipi_flag[this_cpu], 0);
+
+	/*
+	 * Ensure that we've exchanged the vIPI flags before running any IPI
+	 * handler code. This pairs with the first wmb() above.
+	 */
+	rmb();
+
+	for_each_set_bit(i, &firing, AIC_NR_SWIPI) {
+		handle_domain_irq(aic_irqc->ipi_domain, i, regs);
+	}
+
+	aic_ic_write(aic_irqc, AIC_IPI_MASK_CLR, AIC_IPI_OTHER);
+}
+
+static int aic_ipi_alloc(struct irq_domain *d, unsigned int virq,
+			 unsigned int nr_irqs, void *args)
+{
+	int i;
+
+	for (i = 0; i < nr_irqs; i++) {
+		irq_set_percpu_devid(virq + i);
+		irq_domain_set_info(d, virq + i, i, &ipi_chip, d->host_data,
+				    handle_percpu_devid_irq, NULL, NULL);
+	}
+
+	return 0;
+}
+
+static void aic_ipi_free(struct irq_domain *d, unsigned int virq, unsigned int nr_irqs)
+{
+	/* Not freeing IPIs */
+}
+
+static const struct irq_domain_ops aic_ipi_domain_ops = {
+	.alloc = aic_ipi_alloc,
+	.free = aic_ipi_free,
+};
+
+static int aic_init_smp(struct aic_irq_chip *irqc, struct device_node *node)
+{
+	int base_ipi;
+
+	irqc->ipi_domain = irq_domain_create_linear(irqc->hw_domain->fwnode, AIC_NR_SWIPI,
+						    &aic_ipi_domain_ops, irqc);
+	if (WARN_ON(!irqc->ipi_domain))
+		return -ENODEV;
+
+	irqc->ipi_domain->flags |= IRQ_DOMAIN_FLAG_IPI_SINGLE;
+	irq_domain_update_bus_token(irqc->ipi_domain, DOMAIN_BUS_IPI);
+
+	base_ipi = __irq_domain_alloc_irqs(irqc->ipi_domain, -1, AIC_NR_SWIPI,
+					   NUMA_NO_NODE, NULL, false, NULL);
+
+	if (WARN_ON(!base_ipi)) {
+		irq_domain_remove(irqc->ipi_domain);
+		return -ENODEV;
+	}
+
+	set_smp_ipi_range(base_ipi, AIC_NR_SWIPI);
+
+	return 0;
+}
+
+static int aic_init_cpu(unsigned int cpu)
+{
+	/* Mask all hard-wired per-CPU IRQ/FIQ sources */
+
+	/* vGIC maintenance IRQ */
+	sysreg_clear_set_s(SYS_ICH_HCR_EL2, ICH_HCR_EN, 0);
+
+	/* Pending Fast IPI FIQs */
+	write_sysreg_s(IPI_SR_PENDING, SYS_APL_IPI_SR);
+
+	/* Timer FIQs */
+	sysreg_clear_set(cntp_ctl_el0, 0, ARCH_TIMER_CTRL_IT_MASK);
+	sysreg_clear_set(cntv_ctl_el0, 0, ARCH_TIMER_CTRL_IT_MASK);
+	sysreg_clear_set_s(SYS_CNTP_CTL_EL02, 0, ARCH_TIMER_CTRL_IT_MASK);
+	sysreg_clear_set_s(SYS_CNTV_CTL_EL02, 0, ARCH_TIMER_CTRL_IT_MASK);
+
+	/* PMC FIQ */
+	sysreg_clear_set_s(SYS_APL_PMCR0, PMCR0_IMODE | PMCR0_IACT,
+			   FIELD_PREP(PMCR0_IMODE, PMCR0_IMODE_OFF));
+
+	/* Uncore PMC FIQ */
+	sysreg_clear_set_s(SYS_APL_UPMCR0, UPMCR0_IMODE,
+			   FIELD_PREP(UPMCR0_IMODE, UPMCR0_IMODE_OFF));
+
+	/*
+	 * Make sure the kernel's idea of logical CPU order is the same as AIC's
+	 * If we ever end up with a mismatch here, we will have to introduce
+	 * a mapping table similar to what other irqchip drivers do.
+	 */
+	WARN_ON(aic_ic_read(aic_irqc, AIC_WHOAMI) != smp_processor_id());
+
+	return 0;
+
+}
+
+static int __init aic_of_ic_init(struct device_node *node, struct device_node *parent)
+{
+	int i;
+	void __iomem *regs;
+	u32 info;
+	struct aic_irq_chip *irqc;
+
+	regs = of_iomap(node, 0);
+	if (WARN_ON(!regs))
+		return -EIO;
+
+	irqc = kzalloc(sizeof(*irqc), GFP_KERNEL);
+	if (!irqc)
+		return -ENOMEM;
+
+	aic_irqc = irqc;
+	irqc->base = regs;
+
+	info = aic_ic_read(irqc, AIC_INFO);
+	irqc->nr_hw = FIELD_GET(AIC_INFO_NR_HW, info);
+
+	irqc->hw_domain = irq_domain_add_linear(node, irqc->nr_hw + AIC_NR_FIQ,
+						&aic_irq_domain_ops, irqc);
+	if (WARN_ON(!irqc->hw_domain)) {
+		iounmap(irqc->base);
+		kfree(irqc);
+		return -ENODEV;
+	}
+
+	irq_domain_update_bus_token(irqc->hw_domain, DOMAIN_BUS_WIRED);
+
+	if (aic_init_smp(irqc, node)) {
+		irq_domain_remove(irqc->hw_domain);
+		iounmap(irqc->base);
+		kfree(irqc);
+		return -ENODEV;
+	}
+
+	set_handle_irq(aic_handle_irq_or_fiq);
+
+	for (i = 0; i < BITS_TO_U32(irqc->nr_hw); i++)
+		aic_ic_write(irqc, AIC_MASK_SET + i * 4, ~0);
+	for (i = 0; i < BITS_TO_U32(irqc->nr_hw); i++)
+		aic_ic_write(irqc, AIC_SW_CLR + i * 4, ~0);
+	for (i = 0; i < irqc->nr_hw; i++)
+		aic_ic_write(irqc, AIC_TARGET_CPU + i * 4, 1);
+
+	cpuhp_setup_state(CPUHP_AP_IRQ_APPLE_AIC_STARTING,
+			  "irqchip/apple-aic/ipi:starting",
+			  aic_init_cpu, NULL);
+
+	pr_info("AIC: initialized with %d IRQs, %d FIQs, %d vIPIs\n",
+		irqc->nr_hw, AIC_NR_FIQ, AIC_NR_SWIPI);
+
+	return 0;
+}
+
+IRQCHIP_DECLARE(apple_m1_aic, "apple,aic", aic_of_ic_init);
diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
index 0042ef362511..7ea1fc537f12 100644
--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -100,6 +100,7 @@ enum cpuhp_state {
 	CPUHP_AP_CPU_PM_STARTING,
 	CPUHP_AP_IRQ_GIC_STARTING,
 	CPUHP_AP_IRQ_HIP04_STARTING,
+	CPUHP_AP_IRQ_APPLE_AIC_STARTING,
 	CPUHP_AP_IRQ_ARMADA_XP_STARTING,
 	CPUHP_AP_IRQ_BCM2836_STARTING,
 	CPUHP_AP_IRQ_MIPS_GIC_STARTING,
-- 
2.30.0