// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Copyright (C) 2016 Imagination Technologies
 * Author: Paul Burton <paul.burton@mips.com>
 */

#include <linux/delay.h>
#include <linux/io.h>
#include <linux/module.h>
#include <linux/pci.h>
#include <linux/pm.h>

static struct pci_dev *pm_dev;
static resource_size_t io_offset;

enum piix4_pm_io_reg {
        PIIX4_FUNC3IO_PMSTS                     = 0x00,
#define PIIX4_FUNC3IO_PMSTS_PWRBTN_STS          BIT(8)
        PIIX4_FUNC3IO_PMCNTRL                   = 0x04,
#define PIIX4_FUNC3IO_PMCNTRL_SUS_EN            BIT(13)
#define PIIX4_FUNC3IO_PMCNTRL_SUS_TYP_SOFF      (0x0 << 10)
};

#define PIIX4_SUSPEND_MAGIC                     0x00120002

static const int piix4_pm_io_region = PCI_BRIDGE_RESOURCES;

static void piix4_poweroff(void)
{
        int spec_devid;
        u16 sts;

        /* Ensure the power button status is clear */
        while (1) {
                sts = inw(io_offset + PIIX4_FUNC3IO_PMSTS);
                if (!(sts & PIIX4_FUNC3IO_PMSTS_PWRBTN_STS))
                        break;
                outw(sts, io_offset + PIIX4_FUNC3IO_PMSTS);
        }

        /* Enable entry to suspend */
        outw(PIIX4_FUNC3IO_PMCNTRL_SUS_TYP_SOFF | PIIX4_FUNC3IO_PMCNTRL_SUS_EN,
             io_offset + PIIX4_FUNC3IO_PMCNTRL);

        /* If the special cycle occurs too soon this doesn't work... */
        mdelay(10);

        /*
         * The PIIX4 will enter the suspend state only after seeing a special
         * cycle with the correct magic data on the PCI bus. Generate that
         * cycle now.
         */
        spec_devid = PCI_DEVID(0, PCI_DEVFN(0x1f, 0x7));
        pci_bus_write_config_dword(pm_dev->bus, spec_devid, 0,
                                   PIIX4_SUSPEND_MAGIC);

        /* Give the system some time to power down, then error */
        mdelay(1000);
        pr_emerg("Unable to poweroff system\n");
}

static int piix4_poweroff_probe(struct pci_dev *dev,
                                const struct pci_device_id *id)
{
        int res;

        if (pm_dev)
                return -EINVAL;

        /* Request access to the PIIX4 PM IO registers */
        res = pci_request_region(dev, piix4_pm_io_region,
                                 "PIIX4 PM IO registers");
        if (res) {
                dev_err(&dev->dev, "failed to request PM IO registers: %d\n",
                        res);
                return res;
        }

        pm_dev = dev;
        io_offset = pci_resource_start(dev, piix4_pm_io_region);
        pm_power_off = piix4_poweroff;

        return 0;
}

static void piix4_poweroff_remove(struct pci_dev *dev)
{
        if (pm_power_off == piix4_poweroff)
                pm_power_off = NULL;

        pci_release_region(dev, piix4_pm_io_region);
        pm_dev = NULL;
}

static const struct pci_device_id piix4_poweroff_ids[] = {
        { PCI_DEVICE(PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_82371AB_3) },
        { 0 },
};

static struct pci_driver piix4_poweroff_driver = {
        .name           = "piix4-poweroff",
        .id_table       = piix4_poweroff_ids,
        .probe          = piix4_poweroff_probe,
        .remove         = piix4_poweroff_remove,
};

module_pci_driver(piix4_poweroff_driver);
MODULE_AUTHOR("Paul Burton <paul.burton@mips.com>");
MODULE_DESCRIPTION("Intel PIIX4 power-off driver");
MODULE_LICENSE("GPL");