// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2017 SiFive
 * Copyright (C) 2018 Christoph Hellwig
 */
#define pr_fmt(fmt) "plic: " 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/irqdomain.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/of_address.h>
#include <linux/of_irq.h>
#include <linux/platform_device.h>
#include <linux/spinlock.h>
#include <asm/smp.h>

/*
 * This driver implements a version of the RISC-V PLIC with the actual layout
 * specified in chapter 8 of the SiFive U5 Coreplex Series Manual:
 *
 *     https://static.dev.sifive.com/U54-MC-RVCoreIP.pdf
 *
 * The largest number supported by devices marked as 'sifive,plic-1.0.0', is
 * 1024, of which device 0 is defined as non-existent by the RISC-V Privileged
 * Spec.
 */

#define MAX_DEVICES                     1024
#define MAX_CONTEXTS                    15872

/*
 * Each interrupt source has a priority register associated with it.
 * We always hardwire it to one in Linux.
 */
#define PRIORITY_BASE                   0
#define     PRIORITY_PER_ID             4

/*
 * Each hart context has a vector of interrupt enable bits associated with it.
 * There's one bit for each interrupt source.
 */
#define ENABLE_BASE                     0x2000
#define     ENABLE_PER_HART             0x80

/*
 * Each hart context has a set of control registers associated with it.  Right
 * now there's only two: a source priority threshold over which the hart will
 * take an interrupt, and a register to claim interrupts.
 */
#define CONTEXT_BASE                    0x200000
#define     CONTEXT_PER_HART            0x1000
#define     CONTEXT_THRESHOLD           0x00
#define     CONTEXT_CLAIM               0x04

#define PLIC_DISABLE_THRESHOLD          0x7
#define PLIC_ENABLE_THRESHOLD           0

struct plic_priv {
        struct cpumask lmask;
        struct irq_domain *irqdomain;
        void __iomem *regs;
};

struct plic_handler {
        bool                    present;
        void __iomem            *hart_base;
        /*
         * Protect mask operations on the registers given that we can't
         * assume atomic memory operations work on them.
         */
        raw_spinlock_t          enable_lock;
        void __iomem            *enable_base;
        struct plic_priv        *priv;
};
static int plic_parent_irq __ro_after_init;
static bool plic_cpuhp_setup_done __ro_after_init;
static DEFINE_PER_CPU(struct plic_handler, plic_handlers);

static inline void plic_toggle(struct plic_handler *handler,
                                int hwirq, int enable)
{
        u32 __iomem *reg = handler->enable_base + (hwirq / 32) * sizeof(u32);
        u32 hwirq_mask = 1 << (hwirq % 32);

        raw_spin_lock(&handler->enable_lock);
        if (enable)
                writel(readl(reg) | hwirq_mask, reg);
        else
                writel(readl(reg) & ~hwirq_mask, reg);
        raw_spin_unlock(&handler->enable_lock);
}

static inline void plic_irq_toggle(const struct cpumask *mask,
                                   struct irq_data *d, int enable)
{
        int cpu;
        struct plic_priv *priv = irq_data_get_irq_chip_data(d);

        writel(enable, priv->regs + PRIORITY_BASE + d->hwirq * PRIORITY_PER_ID);
        for_each_cpu(cpu, mask) {
                struct plic_handler *handler = per_cpu_ptr(&plic_handlers, cpu);

                if (handler->present &&
                    cpumask_test_cpu(cpu, &handler->priv->lmask))
                        plic_toggle(handler, d->hwirq, enable);
        }
}

static void plic_irq_unmask(struct irq_data *d)
{
        struct cpumask amask;
        unsigned int cpu;
        struct plic_priv *priv = irq_data_get_irq_chip_data(d);

        cpumask_and(&amask, &priv->lmask, cpu_online_mask);
        cpu = cpumask_any_and(irq_data_get_affinity_mask(d),
                                           &amask);
        if (WARN_ON_ONCE(cpu >= nr_cpu_ids))
                return;
        plic_irq_toggle(cpumask_of(cpu), d, 1);
}

static void plic_irq_mask(struct irq_data *d)
{
        struct plic_priv *priv = irq_data_get_irq_chip_data(d);

        plic_irq_toggle(&priv->lmask, d, 0);
}

#ifdef CONFIG_SMP
static int plic_set_affinity(struct irq_data *d,
                             const struct cpumask *mask_val, bool force)
{
        unsigned int cpu;
        struct cpumask amask;
        struct plic_priv *priv = irq_data_get_irq_chip_data(d);

        cpumask_and(&amask, &priv->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;

        plic_irq_toggle(&priv->lmask, d, 0);
        plic_irq_toggle(cpumask_of(cpu), d, !irqd_irq_masked(d));

        irq_data_update_effective_affinity(d, cpumask_of(cpu));

        return IRQ_SET_MASK_OK_DONE;
}
#endif

static void plic_irq_eoi(struct irq_data *d)
{
        struct plic_handler *handler = this_cpu_ptr(&plic_handlers);

        writel(d->hwirq, handler->hart_base + CONTEXT_CLAIM);
}

static struct irq_chip plic_chip = {
        .name           = "SiFive PLIC",
        .irq_mask       = plic_irq_mask,
        .irq_unmask     = plic_irq_unmask,
        .irq_eoi        = plic_irq_eoi,
#ifdef CONFIG_SMP
        .irq_set_affinity = plic_set_affinity,
#endif
};

static int plic_irqdomain_map(struct irq_domain *d, unsigned int irq,
                              irq_hw_number_t hwirq)
{
        struct plic_priv *priv = d->host_data;

        irq_domain_set_info(d, irq, hwirq, &plic_chip, d->host_data,
                            handle_fasteoi_irq, NULL, NULL);
        irq_set_noprobe(irq);
        irq_set_affinity(irq, &priv->lmask);
        return 0;
}

static int plic_irq_domain_alloc(struct irq_domain *domain, unsigned int virq,
                                 unsigned int nr_irqs, void *arg)
{
        int i, ret;
        irq_hw_number_t hwirq;
        unsigned int type;
        struct irq_fwspec *fwspec = arg;

        ret = irq_domain_translate_onecell(domain, fwspec, &hwirq, &type);
        if (ret)
                return ret;

        for (i = 0; i < nr_irqs; i++) {
                ret = plic_irqdomain_map(domain, virq + i, hwirq + i);
                if (ret)
                        return ret;
        }

        return 0;
}

static const struct irq_domain_ops plic_irqdomain_ops = {
        .translate      = irq_domain_translate_onecell,
        .alloc          = plic_irq_domain_alloc,
        .free           = irq_domain_free_irqs_top,
};

/*
 * Handling an interrupt is a two-step process: first you claim the interrupt
 * by reading the claim register, then you complete the interrupt by writing
 * that source ID back to the same claim register.  This automatically enables
 * and disables the interrupt, so there's nothing else to do.
 */
static void plic_handle_irq(struct irq_desc *desc)
{
        struct plic_handler *handler = this_cpu_ptr(&plic_handlers);
        struct irq_chip *chip = irq_desc_get_chip(desc);
        void __iomem *claim = handler->hart_base + CONTEXT_CLAIM;
        irq_hw_number_t hwirq;

        WARN_ON_ONCE(!handler->present);

        chained_irq_enter(chip, desc);

        while ((hwirq = readl(claim))) {
                int irq = irq_find_mapping(handler->priv->irqdomain, hwirq);

                if (unlikely(irq <= 0))
                        pr_warn_ratelimited("can't find mapping for hwirq %lu\n",
                                        hwirq);
                else
                        generic_handle_irq(irq);
        }

        chained_irq_exit(chip, desc);
}

static void plic_set_threshold(struct plic_handler *handler, u32 threshold)
{
        /* priority must be > threshold to trigger an interrupt */
        writel(threshold, handler->hart_base + CONTEXT_THRESHOLD);
}

static int plic_dying_cpu(unsigned int cpu)
{
        if (plic_parent_irq)
                disable_percpu_irq(plic_parent_irq);

        return 0;
}

static int plic_starting_cpu(unsigned int cpu)
{
        struct plic_handler *handler = this_cpu_ptr(&plic_handlers);

        if (plic_parent_irq)
                enable_percpu_irq(plic_parent_irq,
                                  irq_get_trigger_type(plic_parent_irq));
        else
                pr_warn("cpu%d: parent irq not available\n", cpu);
        plic_set_threshold(handler, PLIC_ENABLE_THRESHOLD);

        return 0;
}

static int __init plic_init(struct device_node *node,
                struct device_node *parent)
{
        int error = 0, nr_contexts, nr_handlers = 0, i;
        u32 nr_irqs;
        struct plic_priv *priv;
        struct plic_handler *handler;

        priv = kzalloc(sizeof(*priv), GFP_KERNEL);
        if (!priv)
                return -ENOMEM;

        priv->regs = of_iomap(node, 0);
        if (WARN_ON(!priv->regs)) {
                error = -EIO;
                goto out_free_priv;
        }

        error = -EINVAL;
        of_property_read_u32(node, "riscv,ndev", &nr_irqs);
        if (WARN_ON(!nr_irqs))
                goto out_iounmap;

        nr_contexts = of_irq_count(node);
        if (WARN_ON(!nr_contexts))
                goto out_iounmap;

        error = -ENOMEM;
        priv->irqdomain = irq_domain_add_linear(node, nr_irqs + 1,
                        &plic_irqdomain_ops, priv);
        if (WARN_ON(!priv->irqdomain))
                goto out_iounmap;

        for (i = 0; i < nr_contexts; i++) {
                struct of_phandle_args parent;
                irq_hw_number_t hwirq;
                int cpu, hartid;

                if (of_irq_parse_one(node, i, &parent)) {
                        pr_err("failed to parse parent for context %d.\n", i);
                        continue;
                }

                /*
                 * Skip contexts other than external interrupts for our
                 * privilege level.
                 */
                if (parent.args[0] != RV_IRQ_EXT)
                        continue;

                hartid = riscv_of_parent_hartid(parent.np);
                if (hartid < 0) {
                        pr_warn("failed to parse hart ID for context %d.\n", i);
                        continue;
                }

                cpu = riscv_hartid_to_cpuid(hartid);
                if (cpu < 0) {
                        pr_warn("Invalid cpuid for context %d\n", i);
                        continue;
                }

                /* Find parent domain and register chained handler */
                if (!plic_parent_irq && irq_find_host(parent.np)) {
                        plic_parent_irq = irq_of_parse_and_map(node, i);
                        if (plic_parent_irq)
                                irq_set_chained_handler(plic_parent_irq,
                                                        plic_handle_irq);
                }

                /*
                 * When running in M-mode we need to ignore the S-mode handler.
                 * Here we assume it always comes later, but that might be a
                 * little fragile.
                 */
                handler = per_cpu_ptr(&plic_handlers, cpu);
                if (handler->present) {
                        pr_warn("handler already present for context %d.\n", i);
                        plic_set_threshold(handler, PLIC_DISABLE_THRESHOLD);
                        goto done;
                }

                cpumask_set_cpu(cpu, &priv->lmask);
                handler->present = true;
                handler->hart_base =
                        priv->regs + CONTEXT_BASE + i * CONTEXT_PER_HART;
                raw_spin_lock_init(&handler->enable_lock);
                handler->enable_base =
                        priv->regs + ENABLE_BASE + i * ENABLE_PER_HART;
                handler->priv = priv;
done:
                for (hwirq = 1; hwirq <= nr_irqs; hwirq++)
                        plic_toggle(handler, hwirq, 0);
                nr_handlers++;
        }

        /*
         * We can have multiple PLIC instances so setup cpuhp state only
         * when context handler for current/boot CPU is present.
         */
        handler = this_cpu_ptr(&plic_handlers);
        if (handler->present && !plic_cpuhp_setup_done) {
                cpuhp_setup_state(CPUHP_AP_IRQ_SIFIVE_PLIC_STARTING,
                                  "irqchip/sifive/plic:starting",
                                  plic_starting_cpu, plic_dying_cpu);
                plic_cpuhp_setup_done = true;
        }

        pr_info("%pOFP: mapped %d interrupts with %d handlers for"
                " %d contexts.\n", node, nr_irqs, nr_handlers, nr_contexts);
        return 0;

out_iounmap:
        iounmap(priv->regs);
out_free_priv:
        kfree(priv);
        return error;
}

IRQCHIP_DECLARE(sifive_plic, "sifive,plic-1.0.0", plic_init);
IRQCHIP_DECLARE(riscv_plic0, "riscv,plic0", plic_init); /* for legacy systems */