/*
 * ICS backend for OPAL managed interrupts.
 *
 * Copyright 2011 IBM Corp.
 *
 * 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.
 */

#undef DEBUG

#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/irq.h>
#include <linux/smp.h>
#include <linux/interrupt.h>
#include <linux/init.h>
#include <linux/cpu.h>
#include <linux/of.h>
#include <linux/spinlock.h>
#include <linux/msi.h>

#include <asm/prom.h>
#include <asm/smp.h>
#include <asm/machdep.h>
#include <asm/irq.h>
#include <asm/errno.h>
#include <asm/xics.h>
#include <asm/opal.h>
#include <asm/firmware.h>

static int ics_opal_mangle_server(int server)
{
        /* No link for now */
        return server << 2;
}

static int ics_opal_unmangle_server(int server)
{
        /* No link for now */
        return server >> 2;
}

static void ics_opal_unmask_irq(struct irq_data *d)
{
        unsigned int hw_irq = (unsigned int)irqd_to_hwirq(d);
        int64_t rc;
        int server;

        pr_devel("ics-hal: unmask virq %d [hw 0x%x]\n", d->irq, hw_irq);

        if (hw_irq == XICS_IPI || hw_irq == XICS_IRQ_SPURIOUS)
                return;

        server = xics_get_irq_server(d->irq, irq_data_get_affinity_mask(d), 0);
        server = ics_opal_mangle_server(server);

        rc = opal_set_xive(hw_irq, server, DEFAULT_PRIORITY);
        if (rc != OPAL_SUCCESS)
                pr_err("%s: opal_set_xive(irq=%d [hw 0x%x] server=%x)"
                       " error %lld\n",
                       __func__, d->irq, hw_irq, server, rc);
}

static unsigned int ics_opal_startup(struct irq_data *d)
{
#ifdef CONFIG_PCI_MSI
        /*
         * The generic MSI code returns with the interrupt disabled on the
         * card, using the MSI mask bits. Firmware doesn't appear to unmask
         * at that level, so we do it here by hand.
         */
        if (irq_data_get_msi_desc(d))
                pci_msi_unmask_irq(d);
#endif

        /* unmask it */
        ics_opal_unmask_irq(d);
        return 0;
}

static void ics_opal_mask_real_irq(unsigned int hw_irq)
{
        int server = ics_opal_mangle_server(xics_default_server);
        int64_t rc;

        if (hw_irq == XICS_IPI)
                return;

        /* Have to set XIVE to 0xff to be able to remove a slot */
        rc = opal_set_xive(hw_irq, server, 0xff);
        if (rc != OPAL_SUCCESS)
                pr_err("%s: opal_set_xive(0xff) irq=%u returned %lld\n",
                       __func__, hw_irq, rc);
}

static void ics_opal_mask_irq(struct irq_data *d)
{
        unsigned int hw_irq = (unsigned int)irqd_to_hwirq(d);

        pr_devel("ics-hal: mask virq %d [hw 0x%x]\n", d->irq, hw_irq);

        if (hw_irq == XICS_IPI || hw_irq == XICS_IRQ_SPURIOUS)
                return;
        ics_opal_mask_real_irq(hw_irq);
}

static int ics_opal_set_affinity(struct irq_data *d,
                                 const struct cpumask *cpumask,
                                 bool force)
{
        unsigned int hw_irq = (unsigned int)irqd_to_hwirq(d);
        __be16 oserver;
        int16_t server;
        int8_t priority;
        int64_t rc;
        int wanted_server;

        if (hw_irq == XICS_IPI || hw_irq == XICS_IRQ_SPURIOUS)
                return -1;

        rc = opal_get_xive(hw_irq, &oserver, &priority);
        if (rc != OPAL_SUCCESS) {
                pr_err("%s: opal_get_xive(irq=%d [hw 0x%x]) error %lld\n",
                       __func__, d->irq, hw_irq, rc);
                return -1;
        }
        server = be16_to_cpu(oserver);

        wanted_server = xics_get_irq_server(d->irq, cpumask, 1);
        if (wanted_server < 0) {
                pr_warning("%s: No online cpus in the mask %*pb for irq %d\n",
                           __func__, cpumask_pr_args(cpumask), d->irq);
                return -1;
        }
        server = ics_opal_mangle_server(wanted_server);

        pr_devel("ics-hal: set-affinity irq %d [hw 0x%x] server: 0x%x/0x%x\n",
                 d->irq, hw_irq, wanted_server, server);

        rc = opal_set_xive(hw_irq, server, priority);
        if (rc != OPAL_SUCCESS) {
                pr_err("%s: opal_set_xive(irq=%d [hw 0x%x] server=%x)"
                       " error %lld\n",
                       __func__, d->irq, hw_irq, server, rc);
                return -1;
        }
        return IRQ_SET_MASK_OK;
}

static struct irq_chip ics_opal_irq_chip = {
        .name = "OPAL ICS",
        .irq_startup = ics_opal_startup,
        .irq_mask = ics_opal_mask_irq,
        .irq_unmask = ics_opal_unmask_irq,
        .irq_eoi = NULL, /* Patched at init time */
        .irq_set_affinity = ics_opal_set_affinity
};

static int ics_opal_map(struct ics *ics, unsigned int virq);
static void ics_opal_mask_unknown(struct ics *ics, unsigned long vec);
static long ics_opal_get_server(struct ics *ics, unsigned long vec);

static int ics_opal_host_match(struct ics *ics, struct device_node *node)
{
        return 1;
}

/* Only one global & state struct ics */
static struct ics ics_hal = {
        .map            = ics_opal_map,
        .mask_unknown   = ics_opal_mask_unknown,
        .get_server     = ics_opal_get_server,
        .host_match     = ics_opal_host_match,
};

static int ics_opal_map(struct ics *ics, unsigned int virq)
{
        unsigned int hw_irq = (unsigned int)virq_to_hw(virq);
        int64_t rc;
        __be16 server;
        int8_t priority;

        if (WARN_ON(hw_irq == XICS_IPI || hw_irq == XICS_IRQ_SPURIOUS))
                return -EINVAL;

        /* Check if HAL knows about this interrupt */
        rc = opal_get_xive(hw_irq, &server, &priority);
        if (rc != OPAL_SUCCESS)
                return -ENXIO;

        irq_set_chip_and_handler(virq, &ics_opal_irq_chip, handle_fasteoi_irq);
        irq_set_chip_data(virq, &ics_hal);

        return 0;
}

static void ics_opal_mask_unknown(struct ics *ics, unsigned long vec)
{
        int64_t rc;
        __be16 server;
        int8_t priority;

        /* Check if HAL knows about this interrupt */
        rc = opal_get_xive(vec, &server, &priority);
        if (rc != OPAL_SUCCESS)
                return;

        ics_opal_mask_real_irq(vec);
}

static long ics_opal_get_server(struct ics *ics, unsigned long vec)
{
        int64_t rc;
        __be16 server;
        int8_t priority;

        /* Check if HAL knows about this interrupt */
        rc = opal_get_xive(vec, &server, &priority);
        if (rc != OPAL_SUCCESS)
                return -1;
        return ics_opal_unmangle_server(be16_to_cpu(server));
}

int __init ics_opal_init(void)
{
        if (!firmware_has_feature(FW_FEATURE_OPAL))
                return -ENODEV;

        /* We need to patch our irq chip's EOI to point to the
         * right ICP
         */
        ics_opal_irq_chip.irq_eoi = icp_ops->eoi;

        /* Register ourselves */
        xics_register_ics(&ics_hal);

        pr_info("ICS OPAL backend registered\n");

        return 0;
}