/*
 * Copyright 2011 IBM Corporation.
 *
 *  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.
 *
 */

#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/module.h>

#include <asm/prom.h>
#include <asm/io.h>
#include <asm/smp.h>
#include <asm/irq.h>
#include <asm/errno.h>
#include <asm/xics.h>
#include <asm/kvm_ppc.h>
#include <asm/dbell.h>

struct icp_ipl {
        union {
                u32 word;
                u8 bytes[4];
        } xirr_poll;
        union {
                u32 word;
                u8 bytes[4];
        } xirr;
        u32 dummy;
        union {
                u32 word;
                u8 bytes[4];
        } qirr;
        u32 link_a;
        u32 link_b;
        u32 link_c;
};

static struct icp_ipl __iomem *icp_native_regs[NR_CPUS];

static inline unsigned int icp_native_get_xirr(void)
{
        int cpu = smp_processor_id();
        unsigned int xirr;

        /* Handled an interrupt latched by KVM */
        xirr = kvmppc_get_xics_latch();
        if (xirr)
                return xirr;

        return in_be32(&icp_native_regs[cpu]->xirr.word);
}

static inline void icp_native_set_xirr(unsigned int value)
{
        int cpu = smp_processor_id();

        out_be32(&icp_native_regs[cpu]->xirr.word, value);
}

static inline void icp_native_set_cppr(u8 value)
{
        int cpu = smp_processor_id();

        out_8(&icp_native_regs[cpu]->xirr.bytes[0], value);
}

static inline void icp_native_set_qirr(int n_cpu, u8 value)
{
        out_8(&icp_native_regs[n_cpu]->qirr.bytes[0], value);
}

static void icp_native_set_cpu_priority(unsigned char cppr)
{
        xics_set_base_cppr(cppr);
        icp_native_set_cppr(cppr);
        iosync();
}

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

        iosync();
        icp_native_set_xirr((xics_pop_cppr() << 24) | hw_irq);
}

static void icp_native_teardown_cpu(void)
{
        int cpu = smp_processor_id();

        /* Clear any pending IPI */
        icp_native_set_qirr(cpu, 0xff);
}

static void icp_native_flush_ipi(void)
{
        /* We take the ipi irq but and never return so we
         * need to EOI the IPI, but want to leave our priority 0
         *
         * should we check all the other interrupts too?
         * should we be flagging idle loop instead?
         * or creating some task to be scheduled?
         */

        icp_native_set_xirr((0x00 << 24) | XICS_IPI);
}

static unsigned int icp_native_get_irq(void)
{
        unsigned int xirr = icp_native_get_xirr();
        unsigned int vec = xirr & 0x00ffffff;
        unsigned int irq;

        if (vec == XICS_IRQ_SPURIOUS)
                return 0;

        irq = irq_find_mapping(xics_host, vec);
        if (likely(irq)) {
                xics_push_cppr(vec);
                return irq;
        }

        /* We don't have a linux mapping, so have rtas mask it. */
        xics_mask_unknown_vec(vec);

        /* We might learn about it later, so EOI it */
        icp_native_set_xirr(xirr);

        return 0;
}

#ifdef CONFIG_SMP

static void icp_native_cause_ipi(int cpu)
{
        kvmppc_set_host_ipi(cpu, 1);
        icp_native_set_qirr(cpu, IPI_PRIORITY);
}

#ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE
void icp_native_cause_ipi_rm(int cpu)
{
        /*
         * Currently not used to send IPIs to another CPU
         * on the same core. Only caller is KVM real mode.
         * Need the physical address of the XICS to be
         * previously saved in kvm_hstate in the paca.
         */
        void __iomem *xics_phys;

        /*
         * Just like the cause_ipi functions, it is required to
         * include a full barrier before causing the IPI.
         */
        xics_phys = paca[cpu].kvm_hstate.xics_phys;
        mb();
        __raw_rm_writeb(IPI_PRIORITY, xics_phys + XICS_MFRR);
}
#endif

/*
 * Called when an interrupt is received on an off-line CPU to
 * clear the interrupt, so that the CPU can go back to nap mode.
 */
void icp_native_flush_interrupt(void)
{
        unsigned int xirr = icp_native_get_xirr();
        unsigned int vec = xirr & 0x00ffffff;

        if (vec == XICS_IRQ_SPURIOUS)
                return;
        if (vec == XICS_IPI) {
                /* Clear pending IPI */
                int cpu = smp_processor_id();
                kvmppc_set_host_ipi(cpu, 0);
                icp_native_set_qirr(cpu, 0xff);
        } else {
                pr_err("XICS: hw interrupt 0x%x to offline cpu, disabling\n",
                       vec);
                xics_mask_unknown_vec(vec);
        }
        /* EOI the interrupt */
        icp_native_set_xirr(xirr);
}

void xics_wake_cpu(int cpu)
{
        icp_native_set_qirr(cpu, IPI_PRIORITY);
}
EXPORT_SYMBOL_GPL(xics_wake_cpu);

static irqreturn_t icp_native_ipi_action(int irq, void *dev_id)
{
        int cpu = smp_processor_id();

        kvmppc_set_host_ipi(cpu, 0);
        icp_native_set_qirr(cpu, 0xff);

        return smp_ipi_demux();
}

#endif /* CONFIG_SMP */

static int __init icp_native_map_one_cpu(int hw_id, unsigned long addr,
                                         unsigned long size)
{
        char *rname;
        int i, cpu = -1;

        /* This may look gross but it's good enough for now, we don't quite
         * have a hard -> linux processor id matching.
         */
        for_each_possible_cpu(i) {
                if (!cpu_present(i))
                        continue;
                if (hw_id == get_hard_smp_processor_id(i)) {
                        cpu = i;
                        break;
                }
        }

        /* Fail, skip that CPU. Don't print, it's normal, some XICS come up
         * with way more entries in there than you have CPUs
         */
        if (cpu == -1)
                return 0;

        rname = kasprintf(GFP_KERNEL, "CPU %d [0x%x] Interrupt Presentation",
                          cpu, hw_id);

        if (!request_mem_region(addr, size, rname)) {
                pr_warning("icp_native: Could not reserve ICP MMIO"
                           " for CPU %d, interrupt server #0x%x\n",
                           cpu, hw_id);
                return -EBUSY;
        }

        icp_native_regs[cpu] = ioremap(addr, size);
        kvmppc_set_xics_phys(cpu, addr);
        if (!icp_native_regs[cpu]) {
                pr_warning("icp_native: Failed ioremap for CPU %d, "
                           "interrupt server #0x%x, addr %#lx\n",
                           cpu, hw_id, addr);
                release_mem_region(addr, size);
                return -ENOMEM;
        }
        return 0;
}

static int __init icp_native_init_one_node(struct device_node *np,
                                           unsigned int *indx)
{
        unsigned int ilen;
        const __be32 *ireg;
        int i;
        int reg_tuple_size;
        int num_servers = 0;

        /* This code does the theorically broken assumption that the interrupt
         * server numbers are the same as the hard CPU numbers.
         * This happens to be the case so far but we are playing with fire...
         * should be fixed one of these days. -BenH.
         */
        ireg = of_get_property(np, "ibm,interrupt-server-ranges", &ilen);

        /* Do that ever happen ? we'll know soon enough... but even good'old
         * f80 does have that property ..
         */
        WARN_ON((ireg == NULL) || (ilen != 2*sizeof(u32)));

        if (ireg) {
                *indx = of_read_number(ireg, 1);
                if (ilen >= 2*sizeof(u32))
                        num_servers = of_read_number(ireg + 1, 1);
        }

        ireg = of_get_property(np, "reg", &ilen);
        if (!ireg) {
                pr_err("icp_native: Can't find interrupt reg property");
                return -1;
        }

        reg_tuple_size = (of_n_addr_cells(np) + of_n_size_cells(np)) * 4;
        if (((ilen % reg_tuple_size) != 0)
            || (num_servers && (num_servers != (ilen / reg_tuple_size)))) {
                pr_err("icp_native: ICP reg len (%d) != num servers (%d)",
                       ilen / reg_tuple_size, num_servers);
                return -1;
        }

        for (i = 0; i < (ilen / reg_tuple_size); i++) {
                struct resource r;
                int err;

                err = of_address_to_resource(np, i, &r);
                if (err) {
                        pr_err("icp_native: Could not translate ICP MMIO"
                               " for interrupt server 0x%x (%d)\n", *indx, err);
                        return -1;
                }

                if (icp_native_map_one_cpu(*indx, r.start, resource_size(&r)))
                        return -1;

                (*indx)++;
        }
        return 0;
}

static const struct icp_ops icp_native_ops = {
        .get_irq        = icp_native_get_irq,
        .eoi            = icp_native_eoi,
        .set_priority   = icp_native_set_cpu_priority,
        .teardown_cpu   = icp_native_teardown_cpu,
        .flush_ipi      = icp_native_flush_ipi,
#ifdef CONFIG_SMP
        .ipi_action     = icp_native_ipi_action,
        .cause_ipi      = icp_native_cause_ipi,
#endif
};

int __init icp_native_init(void)
{
        struct device_node *np;
        u32 indx = 0;
        int found = 0;

        for_each_compatible_node(np, NULL, "ibm,ppc-xicp")
                if (icp_native_init_one_node(np, &indx) == 0)
                        found = 1;
        if (!found) {
                for_each_node_by_type(np,
                        "PowerPC-External-Interrupt-Presentation") {
                                if (icp_native_init_one_node(np, &indx) == 0)
                                        found = 1;
                }
        }

        if (found == 0)
                return -ENODEV;

        icp_ops = &icp_native_ops;

        return 0;
}