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Date:   Mon, 25 Sep 2023 13:19:39 +0530
From:   Sunil V L <sunilvl@ventanamicro.com>
To:     Anup Patel <apatel@ventanamicro.com>
Cc:     Palmer Dabbelt <palmer@dabbelt.com>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Marc Zyngier <maz@kernel.org>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Frank Rowand <frowand.list@gmail.com>,
        Conor Dooley <conor+dt@kernel.org>,
        Atish Patra <atishp@atishpatra.org>,
        Andrew Jones <ajones@ventanamicro.com>,
        Saravana Kannan <saravanak@google.com>,
        Anup Patel <anup@brainfault.org>,
        linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
        devicetree@vger.kernel.org
Subject: Re: [PATCH v8 09/16] irqchip: Add RISC-V incoming MSI controller
 early driver
Message-ID: <ZRE7kw4EkWUG4mSq@sunil-laptop>
References: <20230912174928.528414-1-apatel@ventanamicro.com>
 <20230912174928.528414-10-apatel@ventanamicro.com>
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In-Reply-To: <20230912174928.528414-10-apatel@ventanamicro.com>
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Hi Anup,

On Tue, Sep 12, 2023 at 11:19:21PM +0530, Anup Patel wrote:
> 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)
> 
> Let us 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>
> ---
>  drivers/irqchip/Kconfig                 |   7 +-
>  drivers/irqchip/Makefile                |   1 +
>  drivers/irqchip/irq-riscv-imsic-early.c | 258 ++++++++++++
>  drivers/irqchip/irq-riscv-imsic-state.c | 523 ++++++++++++++++++++++++
>  drivers/irqchip/irq-riscv-imsic-state.h |  66 +++
>  include/linux/irqchip/riscv-imsic.h     |  86 ++++
>  6 files changed, 940 insertions(+), 1 deletion(-)
>  create mode 100644 drivers/irqchip/irq-riscv-imsic-early.c
>  create mode 100644 drivers/irqchip/irq-riscv-imsic-state.c
>  create mode 100644 drivers/irqchip/irq-riscv-imsic-state.h
>  create mode 100644 include/linux/irqchip/riscv-imsic.h
> 
> diff --git a/drivers/irqchip/Kconfig b/drivers/irqchip/Kconfig
> index f7149d0f3d45..ee99aacbefcc 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
> @@ -546,6 +545,12 @@ 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..d714724387ce 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-$(CONFIG_RISCV_IMSIC)		+= irq-riscv-imsic-state.o irq-riscv-imsic-early.o
>  obj-$(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-early.c b/drivers/irqchip/irq-riscv-imsic-early.c
> new file mode 100644
> index 000000000000..1de89ce1ec2f
> --- /dev/null
> +++ b/drivers/irqchip/irq-riscv-imsic-early.c
> @@ -0,0 +1,258 @@
> +// 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"
> +
> +/*
> + * 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
> +
> +static int imsic_parent_irq;
> +
> +#ifdef CONFIG_SMP
> +static irqreturn_t imsic_ids_sync_handler(int irq, void *data)
> +{
> +	imsic_ids_local_sync();
> +	return IRQ_HANDLED;
> +}
> +
> +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, cpu_online_mask, cpumask_of(smp_processor_id()));
> +	__ipi_send_mask(imsic->ipi_lsync_desc, &amask);
> +}
> +
> +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);
> +
> +	/* 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)
> +{
> +	/* Clear the IPI id because we are not using IPIs */
> +	imsic->ipi_id = 0;
> +	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);
> +	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;
> +		}
> +
> +		if (unlikely(!imsic->base_domain))
> +			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_early_probe(struct fwnode_handle *fwnode)

Can this imsic_early_probe() take an additional pointer as parameter?
This parameter can be NULL for DT and we can use to pass the MADT
structure in case of ACPI since fwnode in ACPI will not have any
properties. The parameter needs to be passed to imsic_setup_state()
also.

> +{
> +	int rc;
> +	struct irq_domain *domain;
> +
> +	/* Setup IMSIC state */
> +	rc = imsic_setup_state(fwnode);
> +	if (rc) {
> +		pr_err("%pfwP: failed to setup state (error %d)\n",
> +			fwnode, rc);
> +		return 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;
> +	}
> +	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);
> +		return rc;
> +	}
> +
> +	/*
> +	 * 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);
> +
> +	return 0;
> +}
> +
> +static int __init imsic_early_dt_init(struct device_node *node,
> +				      struct device_node *parent)
> +{
> +	int rc;
> +
> +	/* Do early setup of IMSIC state and IPIs */
> +	rc = imsic_early_probe(&node->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);
> diff --git a/drivers/irqchip/irq-riscv-imsic-state.c b/drivers/irqchip/irq-riscv-imsic-state.c
> new file mode 100644
> index 000000000000..412b5b919dcc
> --- /dev/null
> +++ b/drivers/irqchip/irq-riscv-imsic-state.c
> @@ -0,0 +1,523 @@
> +// 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/module.h>
> +#include <linux/of_address.h>
> +#include <linux/spinlock.h>
> +#include <linux/smp.h>
> +#include <asm/hwcap.h>
> +
> +#include "irq-riscv-imsic-state.h"
> +
> +#define IMSIC_DISABLE_EIDELIVERY		0
> +#define IMSIC_ENABLE_EIDELIVERY			1
> +#define IMSIC_DISABLE_EITHRESHOLD		1
> +#define IMSIC_ENABLE_EITHRESHOLD		0
> +
> +#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 *imsic;
> +
> +const struct imsic_global_config *imsic_get_global_config(void)
> +{
> +	return (imsic) ? &imsic->global : NULL;
> +}
> +EXPORT_SYMBOL_GPL(imsic_get_global_config);
> +
> +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);
> +	}
> +}
> +
> +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);
> +}
> +
> +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;
> +}
> +
> +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);
> +}
> +
> +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);
> +	}
> +}
> +
> +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;
> +}
> +
> +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);
> +}
> +
> +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_get_intc_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);
> +}
> +
> +int __init imsic_setup_state(struct fwnode_handle *fwnode)
> +{
> +	int rc, cpu;
> +	phys_addr_t base_addr;
> +	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 -EALREADY;
> +	}
> +
> +	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;
> +	imsic->fwnode = fwnode;
> +	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;
> +	}
> +

Could you create a separate function for DT to fill up this
imsic_global structure? In case of ACPI, we can not get this data from
the fwnode and hence need to have separate function to fill up this
structure.

Thanks!
Sunil
> +	/* 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;
> +		}
> +
> +		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;
> +	}
> +
> +	/* We don't need MMIO arrays anymore so let's free-up */
> +	kfree(mmios_va);
> +	kfree(mmios);
> +
> +	return 0;
> +
> +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;
> +}
> diff --git a/drivers/irqchip/irq-riscv-imsic-state.h b/drivers/irqchip/irq-riscv-imsic-state.h
> new file mode 100644
> index 000000000000..3170018949a8
> --- /dev/null
> +++ b/drivers/irqchip/irq-riscv-imsic-state.h
> @@ -0,0 +1,66 @@
> +/* 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>
> +
> +struct imsic_priv {
> +	/* Device details */
> +	struct fwnode_handle *fwnode;
> +
> +	/* 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;
> +
> +	/* IPI interrupt identity and synchronization */
> +	u32 ipi_id;
> +	int ipi_virq;
> +	struct irq_desc *ipi_lsync_desc;
> +
> +	/* IRQ domains (created by platform driver) */
> +	struct irq_domain *base_domain;
> +	struct irq_domain *plat_domain;
> +};
> +
> +extern struct imsic_priv *imsic;
> +
> +void __imsic_eix_update(unsigned long base_id,
> +			unsigned long num_id, bool pend, bool val);
> +
> +#define __imsic_id_enable(__id)		\
> +	__imsic_eix_update((__id), 1, false, true)
> +#define __imsic_id_disable(__id)	\
> +	__imsic_eix_update((__id), 1, false, false)
> +
> +void imsic_id_set_target(unsigned int id, unsigned int target_cpu);
> +unsigned int imsic_id_get_target(unsigned int id);
> +
> +void imsic_ids_local_sync(void);
> +void imsic_ids_local_delivery(bool enable);
> +
> +#ifdef CONFIG_SMP
> +void imsic_ids_remote_sync(void);
> +#else
> +static inline void imsic_ids_remote_sync(void)
> +{
> +}
> +#endif
> +
> +int imsic_ids_alloc(unsigned int order);
> +void imsic_ids_free(unsigned int base_id, unsigned int order);
> +
> +int imsic_setup_state(struct fwnode_handle *fwnode);
> +
> +#endif
> 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
>