irqchip: Add RISC-V incoming MSI controller early driver

The RISC-V advanced interrupt architecture (AIA) specification
defines a new MSI controller called incoming message signalled
interrupt controller (IMSIC) which manages MSI on per-HART (or
per-CPU) basis. It also supports IPIs as software injected MSIs.
(For more details refer https://github.com/riscv/riscv-aia)

Add an early irqchip driver for RISC-V IMSIC which sets up the
IMSIC state and provide IPIs.
Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Björn Töpel <bjorn@rivosinc.com>
Reviewed-by: Björn Töpel <bjorn@rivosinc.com>
Link: https://lore.kernel.org/r/20240307140307.646078-3-apatel@ventanamicro.com

drivers/irqchip/Kconfig

@@ -540,6 +540,13 @@ config RISCV_INTC
 	depends on RISCV
 	select IRQ_DOMAIN_HIERARCHY
 
+config RISCV_IMSIC
+	bool
+	depends on RISCV
+	select IRQ_DOMAIN_HIERARCHY
+	select GENERIC_IRQ_MATRIX_ALLOCATOR
+	select GENERIC_MSI_IRQ
+
 config SIFIVE_PLIC
 	bool
 	depends on RISCV

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-$(CONFIG_RISCV_IMSIC)		+= irq-riscv-imsic-state.o irq-riscv-imsic-early.o
 obj-$(CONFIG_SIFIVE_PLIC)		+= irq-sifive-plic.o
 obj-$(CONFIG_STARFIVE_JH8100_INTC)	+= irq-starfive-jh8100-intc.o
 obj-$(CONFIG_IMX_IRQSTEER)		+= irq-imx-irqsteer.o

drivers/irqchip/irq-riscv-imsic-early.c

+// 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/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/module.h>
+#include <linux/spinlock.h>
+#include <linux/smp.h>
+
+#include "irq-riscv-imsic-state.h"
+
+static int imsic_parent_irq;
+
+#ifdef CONFIG_SMP
+static void imsic_ipi_send(unsigned int cpu)
+{
+	struct imsic_local_config *local = per_cpu_ptr(imsic->global.local, cpu);
+
+	writel_relaxed(IMSIC_IPI_ID, local->msi_va);
+}
+
+static void imsic_ipi_starting_cpu(void)
+{
+	/* Enable IPIs for current CPU. */
+	__imsic_id_set_enable(IMSIC_IPI_ID);
+}
+
+static void imsic_ipi_dying_cpu(void)
+{
+	/* Disable IPIs for current CPU. */
+	__imsic_id_clear_enable(IMSIC_IPI_ID);
+}
+
+static int __init imsic_ipi_domain_init(void)
+{
+	int virq;
+
+	/* Create IMSIC IPI multiplexing */
+	virq = ipi_mux_create(IMSIC_NR_IPI, imsic_ipi_send);
+	if (virq <= 0)
+		return virq < 0 ? virq : -ENOMEM;
+
+	/* Set vIRQ range */
+	riscv_ipi_set_virq_range(virq, IMSIC_NR_IPI, true);
+
+	/* Announce that IMSIC is providing IPIs */
+	pr_info("%pfwP: providing IPIs using interrupt %d\n", imsic->fwnode, IMSIC_IPI_ID);
+
+	return 0;
+}
+#else
+static void imsic_ipi_starting_cpu(void) { }
+static void imsic_ipi_dying_cpu(void) { }
+static int __init imsic_ipi_domain_init(void) { return 0; }
+#endif
+
+/*
+ * 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);
+	int err, cpu = smp_processor_id();
+	struct imsic_vector *vec;
+	unsigned long local_id;
+
+	chained_irq_enter(chip, desc);
+
+	while ((local_id = csr_swap(CSR_TOPEI, 0))) {
+		local_id >>= TOPEI_ID_SHIFT;
+
+		if (local_id == IMSIC_IPI_ID) {
+			if (IS_ENABLED(CONFIG_SMP))
+				ipi_mux_process();
+			continue;
+		}
+
+		if (unlikely(!imsic->base_domain))
+			continue;
+
+		vec = imsic_vector_from_local_id(cpu, local_id);
+		if (!vec) {
+			pr_warn_ratelimited("vector not found for local ID 0x%lx\n", local_id);
+			continue;
+		}
+
+		err = generic_handle_domain_irq(imsic->base_domain, vec->hwirq);
+		if (unlikely(err))
+			pr_warn_ratelimited("hwirq 0x%x mapping not found\n", vec->hwirq);
+	}
+
+	chained_irq_exit(chip, desc);
+}
+
+static int imsic_starting_cpu(unsigned int cpu)
+{
+	/* Mark per-CPU IMSIC state as online */
+	imsic_state_online();
+
+	/* 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_local_sync_all();
+
+	/* Enable local interrupt delivery */
+	imsic_local_delivery(true);
+
+	return 0;
+}
+
+static int imsic_dying_cpu(unsigned int cpu)
+{
+	/* Cleanup IPIs */
+	imsic_ipi_dying_cpu();
+
+	/* Mark per-CPU IMSIC state as offline */
+	imsic_state_offline();
+
+	return 0;
+}
+
+static int __init imsic_early_probe(struct fwnode_handle *fwnode)
+{
+	struct irq_domain *domain;
+	int rc;
+
+	/* 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);
+		return -ENOENT;
+	}
+	imsic_parent_irq = irq_create_mapping(domain, RV_IRQ_EXT);
+	if (!imsic_parent_irq) {
+		pr_err("%pfwP: Failed to create INTC mapping\n", fwnode);
+		return -ENOENT;
+	}
+
+	/* Initialize IPI domain */
+	rc = imsic_ipi_domain_init();
+	if (rc) {
+		pr_err("%pfwP: Failed to initialize IPI domain\n", fwnode);
+		return rc;
+	}
+
+	/* Setup chained handler to the parent domain interrupt */
+	irq_set_chained_handler(imsic_parent_irq, imsic_handle_irq);
+
+	/*
+	 * 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_IRQ_RISCV_IMSIC_STARTING, "irqchip/riscv/imsic:starting",
+			  imsic_starting_cpu, imsic_dying_cpu);
+
+	return 0;
+}
+
+static int __init imsic_early_dt_init(struct device_node *node, struct device_node *parent)
+{
+	struct fwnode_handle *fwnode = &node->fwnode;
+	int rc;
+
+	/* Setup IMSIC state */
+	rc = imsic_setup_state(fwnode);
+	if (rc) {
+		pr_err("%pfwP: failed to setup state (error %d)\n", fwnode, rc);
+		return rc;
+	}
+
+	/* Do early setup of IPIs */
+	rc = imsic_early_probe(fwnode);
+	if (rc)
+		return rc;
+
+	/* Ensure that OF platform device gets probed */
+	of_node_clear_flag(node, OF_POPULATED);
+	return 0;
+}
+
+IRQCHIP_DECLARE(riscv_imsic, "riscv,imsics", imsic_early_dt_init);

drivers/irqchip/irq-riscv-imsic-state.h

+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2021 Western Digital Corporation or its affiliates.
+ * Copyright (C) 2022 Ventana Micro Systems Inc.
+ */
+
+#ifndef _IRQ_RISCV_IMSIC_STATE_H
+#define _IRQ_RISCV_IMSIC_STATE_H
+
+#include <linux/irqchip/riscv-imsic.h>
+#include <linux/irqdomain.h>
+#include <linux/fwnode.h>
+#include <linux/timer.h>
+
+#define IMSIC_IPI_ID				1
+#define IMSIC_NR_IPI				8
+
+struct imsic_vector {
+	/* Fixed details of the vector */
+	unsigned int				cpu;
+	unsigned int				local_id;
+	/* Details saved by driver in the vector */
+	unsigned int				hwirq;
+	/* Details accessed using local lock held */
+	bool					enable;
+	struct imsic_vector			*move;
+};
+
+struct imsic_local_priv {
+	/* Local lock to protect vector enable/move variables and dirty bitmap */
+	raw_spinlock_t				lock;
+
+	/* Local dirty bitmap for synchronization */
+	unsigned long				*dirty_bitmap;
+
+#ifdef CONFIG_SMP
+	/* Local timer for synchronization */
+	struct timer_list			timer;
+#endif
+
+	/* Local vector table */
+	struct imsic_vector			*vectors;
+};
+
+struct imsic_priv {
+	/* Device details */
+	struct fwnode_handle			*fwnode;
+
+	/* Global configuration common for all HARTs */
+	struct imsic_global_config		global;
+
+	/* Per-CPU state */
+	struct imsic_local_priv __percpu	*lpriv;
+
+	/* State of IRQ matrix allocator */
+	raw_spinlock_t				matrix_lock;
+	struct irq_matrix			*matrix;
+
+	/* IRQ domains (created by platform driver) */
+	struct irq_domain			*base_domain;
+};
+
+extern struct imsic_priv *imsic;
+
+void __imsic_eix_update(unsigned long base_id, unsigned long num_id, bool pend, bool val);
+
+static inline void __imsic_id_set_enable(unsigned long id)
+{
+	__imsic_eix_update(id, 1, false, true);
+}
+
+static inline void __imsic_id_clear_enable(unsigned long id)
+{
+	__imsic_eix_update(id, 1, false, false);
+}
+
+void imsic_local_sync_all(void);
+void imsic_local_delivery(bool enable);
+
+void imsic_vector_mask(struct imsic_vector *vec);
+void imsic_vector_unmask(struct imsic_vector *vec);
+
+static inline bool imsic_vector_isenabled(struct imsic_vector *vec)
+{
+	return READ_ONCE(vec->enable);
+}
+
+static inline struct imsic_vector *imsic_vector_get_move(struct imsic_vector *vec)
+{
+	return READ_ONCE(vec->move);
+}
+
+void imsic_vector_move(struct imsic_vector *old_vec, struct imsic_vector *new_vec);
+
+struct imsic_vector *imsic_vector_from_local_id(unsigned int cpu, unsigned int local_id);
+
+struct imsic_vector *imsic_vector_alloc(unsigned int hwirq, const struct cpumask *mask);
+void imsic_vector_free(struct imsic_vector *vector);
+
+void imsic_vector_debug_show(struct seq_file *m, struct imsic_vector *vec, int ind);
+void imsic_vector_debug_show_summary(struct seq_file *m, int ind);
+
+void imsic_state_online(void);
+void imsic_state_offline(void);
+int imsic_setup_state(struct fwnode_handle *fwnode);
+
+#endif

include/linux/cpuhotplug.h

@@ -146,6 +146,7 @@ enum cpuhp_state {
 	CPUHP_AP_IRQ_MIPS_GIC_STARTING,
 	CPUHP_AP_IRQ_LOONGARCH_STARTING,
 	CPUHP_AP_IRQ_SIFIVE_PLIC_STARTING,
+	CPUHP_AP_IRQ_RISCV_IMSIC_STARTING,
 	CPUHP_AP_ARM_MVEBU_COHERENCY,
 	CPUHP_AP_PERF_X86_AMD_UNCORE_STARTING,
 	CPUHP_AP_PERF_X86_STARTING,

include/linux/irqchip/riscv-imsic.h

+/* 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 <linux/bitops.h>
+#include <asm/csr.h>
+
+#define IMSIC_MMIO_PAGE_SHIFT		12
+#define IMSIC_MMIO_PAGE_SZ		BIT(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
+
+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