/*
 * APM X-Gene MSI Driver
 *
 * Copyright (c) 2014, Applied Micro Circuits Corporation
 * Author: Tanmay Inamdar <tinamdar@apm.com>
 *         Duc Dang <dhdang@apm.com>
 *
 * This program is free software; you can redistribute  it and/or modify it
 * under  the terms of  the GNU General  Public License as published by the
 * Free Software Foundation;  either version 2 of the  License, or (at your
 * option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 */
#include <linux/cpu.h>
#include <linux/interrupt.h>
#include <linux/module.h>
#include <linux/msi.h>
#include <linux/of_irq.h>
#include <linux/irqchip/chained_irq.h>
#include <linux/pci.h>
#include <linux/platform_device.h>
#include <linux/of_pci.h>

#define MSI_IR0                 0x000000
#define MSI_INT0                0x800000
#define IDX_PER_GROUP           8
#define IRQS_PER_IDX            16
#define NR_HW_IRQS              16
#define NR_MSI_VEC              (IDX_PER_GROUP * IRQS_PER_IDX * NR_HW_IRQS)

struct xgene_msi_group {
        struct xgene_msi        *msi;
        int                     gic_irq;
        u32                     msi_grp;
};

struct xgene_msi {
        struct device_node      *node;
        struct msi_controller   mchip;
        struct irq_domain       *domain;
        u64                     msi_addr;
        void __iomem            *msi_regs;
        unsigned long           *bitmap;
        struct mutex            bitmap_lock;
        struct xgene_msi_group  *msi_groups;
        int                     num_cpus;
};

/* Global data */
static struct xgene_msi xgene_msi_ctrl;

static struct irq_chip xgene_msi_top_irq_chip = {
        .name           = "X-Gene1 MSI",
        .irq_enable     = pci_msi_unmask_irq,
        .irq_disable    = pci_msi_mask_irq,
        .irq_mask       = pci_msi_mask_irq,
        .irq_unmask     = pci_msi_unmask_irq,
};

static struct  msi_domain_info xgene_msi_domain_info = {
        .flags  = (MSI_FLAG_USE_DEF_DOM_OPS | MSI_FLAG_USE_DEF_CHIP_OPS |
                  MSI_FLAG_PCI_MSIX),
        .chip   = &xgene_msi_top_irq_chip,
};

/*
 * X-Gene v1 has 16 groups of MSI termination registers MSInIRx, where
 * n is group number (0..F), x is index of registers in each group (0..7)
 * The register layout is as follows:
 * MSI0IR0                      base_addr
 * MSI0IR1                      base_addr +  0x10000
 * ...                          ...
 * MSI0IR6                      base_addr +  0x60000
 * MSI0IR7                      base_addr +  0x70000
 * MSI1IR0                      base_addr +  0x80000
 * MSI1IR1                      base_addr +  0x90000
 * ...                          ...
 * MSI1IR7                      base_addr +  0xF0000
 * MSI2IR0                      base_addr + 0x100000
 * ...                          ...
 * MSIFIR0                      base_addr + 0x780000
 * MSIFIR1                      base_addr + 0x790000
 * ...                          ...
 * MSIFIR7                      base_addr + 0x7F0000
 * MSIINT0                      base_addr + 0x800000
 * MSIINT1                      base_addr + 0x810000
 * ...                          ...
 * MSIINTF                      base_addr + 0x8F0000
 *
 * Each index register supports 16 MSI vectors (0..15) to generate interrupt.
 * There are total 16 GIC IRQs assigned for these 16 groups of MSI termination
 * registers.
 *
 * Each MSI termination group has 1 MSIINTn register (n is 0..15) to indicate
 * the MSI pending status caused by 1 of its 8 index registers.
 */

/* MSInIRx read helper */
static u32 xgene_msi_ir_read(struct xgene_msi *msi,
                                    u32 msi_grp, u32 msir_idx)
{
        return readl_relaxed(msi->msi_regs + MSI_IR0 +
                              (msi_grp << 19) + (msir_idx << 16));
}

/* MSIINTn read helper */
static u32 xgene_msi_int_read(struct xgene_msi *msi, u32 msi_grp)
{
        return readl_relaxed(msi->msi_regs + MSI_INT0 + (msi_grp << 16));
}

/*
 * With 2048 MSI vectors supported, the MSI message can be constructed using
 * following scheme:
 * - Divide into 8 256-vector groups
 *              Group 0: 0-255
 *              Group 1: 256-511
 *              Group 2: 512-767
 *              ...
 *              Group 7: 1792-2047
 * - Each 256-vector group is divided into 16 16-vector groups
 *      As an example: 16 16-vector groups for 256-vector group 0-255 is
 *              Group 0: 0-15
 *              Group 1: 16-32
 *              ...
 *              Group 15: 240-255
 * - The termination address of MSI vector in 256-vector group n and 16-vector
 *   group x is the address of MSIxIRn
 * - The data for MSI vector in 16-vector group x is x
 */
static u32 hwirq_to_reg_set(unsigned long hwirq)
{
        return (hwirq / (NR_HW_IRQS * IRQS_PER_IDX));
}

static u32 hwirq_to_group(unsigned long hwirq)
{
        return (hwirq % NR_HW_IRQS);
}

static u32 hwirq_to_msi_data(unsigned long hwirq)
{
        return ((hwirq / NR_HW_IRQS) % IRQS_PER_IDX);
}

static void xgene_compose_msi_msg(struct irq_data *data, struct msi_msg *msg)
{
        struct xgene_msi *msi = irq_data_get_irq_chip_data(data);
        u32 reg_set = hwirq_to_reg_set(data->hwirq);
        u32 group = hwirq_to_group(data->hwirq);
        u64 target_addr = msi->msi_addr + (((8 * group) + reg_set) << 16);

        msg->address_hi = upper_32_bits(target_addr);
        msg->address_lo = lower_32_bits(target_addr);
        msg->data = hwirq_to_msi_data(data->hwirq);
}

/*
 * X-Gene v1 only has 16 MSI GIC IRQs for 2048 MSI vectors.  To maintain
 * the expected behaviour of .set_affinity for each MSI interrupt, the 16
 * MSI GIC IRQs are statically allocated to 8 X-Gene v1 cores (2 GIC IRQs
 * for each core).  The MSI vector is moved fom 1 MSI GIC IRQ to another
 * MSI GIC IRQ to steer its MSI interrupt to correct X-Gene v1 core.  As a
 * consequence, the total MSI vectors that X-Gene v1 supports will be
 * reduced to 256 (2048/8) vectors.
 */
static int hwirq_to_cpu(unsigned long hwirq)
{
        return (hwirq % xgene_msi_ctrl.num_cpus);
}

static unsigned long hwirq_to_canonical_hwirq(unsigned long hwirq)
{
        return (hwirq - hwirq_to_cpu(hwirq));
}

static int xgene_msi_set_affinity(struct irq_data *irqdata,
                                  const struct cpumask *mask, bool force)
{
        int target_cpu = cpumask_first(mask);
        int curr_cpu;

        curr_cpu = hwirq_to_cpu(irqdata->hwirq);
        if (curr_cpu == target_cpu)
                return IRQ_SET_MASK_OK_DONE;

        /* Update MSI number to target the new CPU */
        irqdata->hwirq = hwirq_to_canonical_hwirq(irqdata->hwirq) + target_cpu;

        return IRQ_SET_MASK_OK;
}

static struct irq_chip xgene_msi_bottom_irq_chip = {
        .name                   = "MSI",
        .irq_set_affinity       = xgene_msi_set_affinity,
        .irq_compose_msi_msg    = xgene_compose_msi_msg,
};

static int xgene_irq_domain_alloc(struct irq_domain *domain, unsigned int virq,
                                  unsigned int nr_irqs, void *args)
{
        struct xgene_msi *msi = domain->host_data;
        int msi_irq;

        mutex_lock(&msi->bitmap_lock);

        msi_irq = bitmap_find_next_zero_area(msi->bitmap, NR_MSI_VEC, 0,
                                             msi->num_cpus, 0);
        if (msi_irq < NR_MSI_VEC)
                bitmap_set(msi->bitmap, msi_irq, msi->num_cpus);
        else
                msi_irq = -ENOSPC;

        mutex_unlock(&msi->bitmap_lock);

        if (msi_irq < 0)
                return msi_irq;

        irq_domain_set_info(domain, virq, msi_irq,
                            &xgene_msi_bottom_irq_chip, domain->host_data,
                            handle_simple_irq, NULL, NULL);
        set_irq_flags(virq, IRQF_VALID);

        return 0;
}

static void xgene_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);
        struct xgene_msi *msi = irq_data_get_irq_chip_data(d);
        u32 hwirq;

        mutex_lock(&msi->bitmap_lock);

        hwirq = hwirq_to_canonical_hwirq(d->hwirq);
        bitmap_clear(msi->bitmap, hwirq, msi->num_cpus);

        mutex_unlock(&msi->bitmap_lock);

        irq_domain_free_irqs_parent(domain, virq, nr_irqs);
}

static const struct irq_domain_ops msi_domain_ops = {
        .alloc  = xgene_irq_domain_alloc,
        .free   = xgene_irq_domain_free,
};

static int xgene_allocate_domains(struct xgene_msi *msi)
{
        msi->domain = irq_domain_add_linear(NULL, NR_MSI_VEC,
                                            &msi_domain_ops, msi);
        if (!msi->domain)
                return -ENOMEM;

        msi->mchip.domain = pci_msi_create_irq_domain(msi->mchip.of_node,
                                                      &xgene_msi_domain_info,
                                                      msi->domain);

        if (!msi->mchip.domain) {
                irq_domain_remove(msi->domain);
                return -ENOMEM;
        }

        return 0;
}

static void xgene_free_domains(struct xgene_msi *msi)
{
        if (msi->mchip.domain)
                irq_domain_remove(msi->mchip.domain);
        if (msi->domain)
                irq_domain_remove(msi->domain);
}

static int xgene_msi_init_allocator(struct xgene_msi *xgene_msi)
{
        int size = BITS_TO_LONGS(NR_MSI_VEC) * sizeof(long);

        xgene_msi->bitmap = kzalloc(size, GFP_KERNEL);
        if (!xgene_msi->bitmap)
                return -ENOMEM;

        mutex_init(&xgene_msi->bitmap_lock);

        xgene_msi->msi_groups = kcalloc(NR_HW_IRQS,
                                        sizeof(struct xgene_msi_group),
                                        GFP_KERNEL);
        if (!xgene_msi->msi_groups)
                return -ENOMEM;

        return 0;
}

static void xgene_msi_isr(unsigned int irq, struct irq_desc *desc)
{
        struct irq_chip *chip = irq_desc_get_chip(desc);
        struct xgene_msi_group *msi_groups;
        struct xgene_msi *xgene_msi;
        unsigned int virq;
        int msir_index, msir_val, hw_irq;
        u32 intr_index, grp_select, msi_grp;

        chained_irq_enter(chip, desc);

        msi_groups = irq_desc_get_handler_data(desc);
        xgene_msi = msi_groups->msi;
        msi_grp = msi_groups->msi_grp;

        /*
         * MSIINTn (n is 0..F) indicates if there is a pending MSI interrupt
         * If bit x of this register is set (x is 0..7), one or more interupts
         * corresponding to MSInIRx is set.
         */
        grp_select = xgene_msi_int_read(xgene_msi, msi_grp);
        while (grp_select) {
                msir_index = ffs(grp_select) - 1;
                /*
                 * Calculate MSInIRx address to read to check for interrupts
                 * (refer to termination address and data assignment
                 * described in xgene_compose_msi_msg() )
                 */
                msir_val = xgene_msi_ir_read(xgene_msi, msi_grp, msir_index);
                while (msir_val) {
                        intr_index = ffs(msir_val) - 1;
                        /*
                         * Calculate MSI vector number (refer to the termination
                         * address and data assignment described in
                         * xgene_compose_msi_msg function)
                         */
                        hw_irq = (((msir_index * IRQS_PER_IDX) + intr_index) *
                                 NR_HW_IRQS) + msi_grp;
                        /*
                         * As we have multiple hw_irq that maps to single MSI,
                         * always look up the virq using the hw_irq as seen from
                         * CPU0
                         */
                        hw_irq = hwirq_to_canonical_hwirq(hw_irq);
                        virq = irq_find_mapping(xgene_msi->domain, hw_irq);
                        WARN_ON(!virq);
                        if (virq != 0)
                                generic_handle_irq(virq);
                        msir_val &= ~(1 << intr_index);
                }
                grp_select &= ~(1 << msir_index);

                if (!grp_select) {
                        /*
                         * We handled all interrupts happened in this group,
                         * resample this group MSI_INTx register in case
                         * something else has been made pending in the meantime
                         */
                        grp_select = xgene_msi_int_read(xgene_msi, msi_grp);
                }
        }

        chained_irq_exit(chip, desc);
}

static int xgene_msi_remove(struct platform_device *pdev)
{
        int virq, i;
        struct xgene_msi *msi = platform_get_drvdata(pdev);

        for (i = 0; i < NR_HW_IRQS; i++) {
                virq = msi->msi_groups[i].gic_irq;
                if (virq != 0) {
                        irq_set_chained_handler(virq, NULL);
                        irq_set_handler_data(virq, NULL);
                }
        }
        kfree(msi->msi_groups);

        kfree(msi->bitmap);
        msi->bitmap = NULL;

        xgene_free_domains(msi);

        return 0;
}

static int xgene_msi_hwirq_alloc(unsigned int cpu)
{
        struct xgene_msi *msi = &xgene_msi_ctrl;
        struct xgene_msi_group *msi_group;
        cpumask_var_t mask;
        int i;
        int err;

        for (i = cpu; i < NR_HW_IRQS; i += msi->num_cpus) {
                msi_group = &msi->msi_groups[i];
                if (!msi_group->gic_irq)
                        continue;

                irq_set_chained_handler(msi_group->gic_irq,
                                        xgene_msi_isr);
                err = irq_set_handler_data(msi_group->gic_irq, msi_group);
                if (err) {
                        pr_err("failed to register GIC IRQ handler\n");
                        return -EINVAL;
                }
                /*
                 * Statically allocate MSI GIC IRQs to each CPU core.
                 * With 8-core X-Gene v1, 2 MSI GIC IRQs are allocated
                 * to each core.
                 */
                if (alloc_cpumask_var(&mask, GFP_KERNEL)) {
                        cpumask_clear(mask);
                        cpumask_set_cpu(cpu, mask);
                        err = irq_set_affinity(msi_group->gic_irq, mask);
                        if (err)
                                pr_err("failed to set affinity for GIC IRQ");
                        free_cpumask_var(mask);
                } else {
                        pr_err("failed to alloc CPU mask for affinity\n");
                        err = -EINVAL;
                }

                if (err) {
                        irq_set_chained_handler(msi_group->gic_irq, NULL);
                        irq_set_handler_data(msi_group->gic_irq, NULL);
                        return err;
                }
        }

        return 0;
}

static void xgene_msi_hwirq_free(unsigned int cpu)
{
        struct xgene_msi *msi = &xgene_msi_ctrl;
        struct xgene_msi_group *msi_group;
        int i;

        for (i = cpu; i < NR_HW_IRQS; i += msi->num_cpus) {
                msi_group = &msi->msi_groups[i];
                if (!msi_group->gic_irq)
                        continue;

                irq_set_chained_handler(msi_group->gic_irq, NULL);
                irq_set_handler_data(msi_group->gic_irq, NULL);
        }
}

static int xgene_msi_cpu_callback(struct notifier_block *nfb,
                                  unsigned long action, void *hcpu)
{
        unsigned cpu = (unsigned long)hcpu;

        switch (action) {
        case CPU_ONLINE:
        case CPU_ONLINE_FROZEN:
                xgene_msi_hwirq_alloc(cpu);
                break;
        case CPU_DEAD:
        case CPU_DEAD_FROZEN:
                xgene_msi_hwirq_free(cpu);
                break;
        default:
                break;
        }

        return NOTIFY_OK;
}

static struct notifier_block xgene_msi_cpu_notifier = {
        .notifier_call = xgene_msi_cpu_callback,
};

static const struct of_device_id xgene_msi_match_table[] = {
        {.compatible = "apm,xgene1-msi"},
        {},
};

static int xgene_msi_probe(struct platform_device *pdev)
{
        struct resource *res;
        int rc, irq_index;
        struct xgene_msi *xgene_msi;
        unsigned int cpu;
        int virt_msir;
        u32 msi_val, msi_idx;

        xgene_msi = &xgene_msi_ctrl;

        platform_set_drvdata(pdev, xgene_msi);

        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        xgene_msi->msi_regs = devm_ioremap_resource(&pdev->dev, res);
        if (IS_ERR(xgene_msi->msi_regs)) {
                dev_err(&pdev->dev, "no reg space\n");
                rc = -EINVAL;
                goto error;
        }
        xgene_msi->msi_addr = res->start;

        xgene_msi->num_cpus = num_possible_cpus();

        rc = xgene_msi_init_allocator(xgene_msi);
        if (rc) {
                dev_err(&pdev->dev, "Error allocating MSI bitmap\n");
                goto error;
        }

        rc = xgene_allocate_domains(xgene_msi);
        if (rc) {
                dev_err(&pdev->dev, "Failed to allocate MSI domain\n");
                goto error;
        }

        for (irq_index = 0; irq_index < NR_HW_IRQS; irq_index++) {
                virt_msir = platform_get_irq(pdev, irq_index);
                if (virt_msir < 0) {
                        dev_err(&pdev->dev, "Cannot translate IRQ index %d\n",
                                irq_index);
                        rc = -EINVAL;
                        goto error;
                }
                xgene_msi->msi_groups[irq_index].gic_irq = virt_msir;
                xgene_msi->msi_groups[irq_index].msi_grp = irq_index;
                xgene_msi->msi_groups[irq_index].msi = xgene_msi;
        }

        /*
         * MSInIRx registers are read-to-clear; before registering
         * interrupt handlers, read all of them to clear spurious
         * interrupts that may occur before the driver is probed.
         */
        for (irq_index = 0; irq_index < NR_HW_IRQS; irq_index++) {
                for (msi_idx = 0; msi_idx < IDX_PER_GROUP; msi_idx++)
                        msi_val = xgene_msi_ir_read(xgene_msi, irq_index,
                                                    msi_idx);
                /* Read MSIINTn to confirm */
                msi_val = xgene_msi_int_read(xgene_msi, irq_index);
                if (msi_val) {
                        dev_err(&pdev->dev, "Failed to clear spurious IRQ\n");
                        rc = -EINVAL;
                        goto error;
                }
        }

        cpu_notifier_register_begin();

        for_each_online_cpu(cpu)
                if (xgene_msi_hwirq_alloc(cpu)) {
                        dev_err(&pdev->dev, "failed to register MSI handlers\n");
                        cpu_notifier_register_done();
                        goto error;
                }

        rc = __register_hotcpu_notifier(&xgene_msi_cpu_notifier);
        if (rc) {
                dev_err(&pdev->dev, "failed to add CPU MSI notifier\n");
                cpu_notifier_register_done();
                goto error;
        }

        cpu_notifier_register_done();

        xgene_msi->mchip.of_node = pdev->dev.of_node;
        rc = of_pci_msi_chip_add(&xgene_msi->mchip);
        if (rc) {
                dev_err(&pdev->dev, "failed to add MSI controller chip\n");
                goto error_notifier;
        }

        dev_info(&pdev->dev, "APM X-Gene PCIe MSI driver loaded\n");

        return 0;

error_notifier:
        unregister_hotcpu_notifier(&xgene_msi_cpu_notifier);
error:
        xgene_msi_remove(pdev);
        return rc;
}

static struct platform_driver xgene_msi_driver = {
        .driver = {
                .name = "xgene-msi",
                .owner = THIS_MODULE,
                .of_match_table = xgene_msi_match_table,
        },
        .probe = xgene_msi_probe,
        .remove = xgene_msi_remove,
};

static int __init xgene_pcie_msi_init(void)
{
        return platform_driver_register(&xgene_msi_driver);
}
subsys_initcall(xgene_pcie_msi_init);