/*
 * OpRegion handler to allow AML to call native firmware
 *
 * (c) Copyright 2007 Hewlett-Packard Development Company, L.P.
 *      Bjorn Helgaas <bjorn.helgaas@hp.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * This driver implements HP Open Source Review Board proposal 1842,
 * which was approved on 9/20/2006.
 *
 * For technical documentation, see the HP SPPA Firmware EAS, Appendix F.
 *
 * ACPI does not define a mechanism for AML methods to call native firmware
 * interfaces such as PAL or SAL.  This OpRegion handler adds such a mechanism.
 * After the handler is installed, an AML method can call native firmware by
 * storing the arguments and firmware entry point to specific offsets in the
 * OpRegion.  When AML reads the "return value" offset from the OpRegion, this
 * handler loads up the arguments, makes the firmware call, and returns the
 * result.
 */

#include <linux/module.h>
#include <linux/acpi.h>
#include <asm/sal.h>

MODULE_AUTHOR("Bjorn Helgaas <bjorn.helgaas@hp.com>");
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("ACPI opregion handler for native firmware calls");

static bool force_register;
module_param_named(force, force_register, bool, 0);
MODULE_PARM_DESC(force, "Install opregion handler even without HPQ5001 device");

#define AML_NFW_SPACE           0xA1

struct ia64_pdesc {
        void *ip;
        void *gp;
};

/*
 * N.B.  The layout of this structure is defined in the HP SPPA FW EAS, and
 *       the member offsets are embedded in AML methods.
 */
struct ia64_nfw_context {
        u64 arg[8];
        struct ia64_sal_retval ret;
        u64 ip;
        u64 gp;
        u64 pad[2];
};

static void *virt_map(u64 address)
{
        if (address & (1UL << 63))
                return (void *) (__IA64_UNCACHED_OFFSET | address);

        return __va(address);
}

static void aml_nfw_execute(struct ia64_nfw_context *c)
{
        struct ia64_pdesc virt_entry;
        ia64_sal_handler entry;

        virt_entry.ip = virt_map(c->ip);
        virt_entry.gp = virt_map(c->gp);

        entry = (ia64_sal_handler) &virt_entry;

        IA64_FW_CALL(entry, c->ret,
                     c->arg[0], c->arg[1], c->arg[2], c->arg[3],
                     c->arg[4], c->arg[5], c->arg[6], c->arg[7]);
}

static void aml_nfw_read_arg(u8 *offset, u32 bit_width, u64 *value)
{
        switch (bit_width) {
        case 8:
                *value = *(u8 *)offset;
                break;
        case 16:
                *value = *(u16 *)offset;
                break;
        case 32:
                *value = *(u32 *)offset;
                break;
        case 64:
                *value = *(u64 *)offset;
                break;
        }
}

static void aml_nfw_write_arg(u8 *offset, u32 bit_width, u64 *value)
{
        switch (bit_width) {
        case 8:
                *(u8 *) offset = *value;
                break;
        case 16:
                *(u16 *) offset = *value;
                break;
        case 32:
                *(u32 *) offset = *value;
                break;
        case 64:
                *(u64 *) offset = *value;
                break;
        }
}

static acpi_status aml_nfw_handler(u32 function, acpi_physical_address address,
        u32 bit_width, u64 *value, void *handler_context,
        void *region_context)
{
        struct ia64_nfw_context *context = handler_context;
        u8 *offset = (u8 *) context + address;

        if (bit_width !=  8 && bit_width != 16 &&
            bit_width != 32 && bit_width != 64)
                return AE_BAD_PARAMETER;

        if (address + (bit_width >> 3) > sizeof(struct ia64_nfw_context))
                return AE_BAD_PARAMETER;

        switch (function) {
        case ACPI_READ:
                if (address == offsetof(struct ia64_nfw_context, ret))
                        aml_nfw_execute(context);
                aml_nfw_read_arg(offset, bit_width, value);
                break;
        case ACPI_WRITE:
                aml_nfw_write_arg(offset, bit_width, value);
                break;
        }

        return AE_OK;
}

static struct ia64_nfw_context global_context;
static int global_handler_registered;

static int aml_nfw_add_global_handler(void)
{
        acpi_status status;

        if (global_handler_registered)
                return 0;

        status = acpi_install_address_space_handler(ACPI_ROOT_OBJECT,
                AML_NFW_SPACE, aml_nfw_handler, NULL, &global_context);
        if (ACPI_FAILURE(status))
                return -ENODEV;

        global_handler_registered = 1;
        printk(KERN_INFO "Global 0x%02X opregion handler registered\n",
                AML_NFW_SPACE);
        return 0;
}

static int aml_nfw_remove_global_handler(void)
{
        acpi_status status;

        if (!global_handler_registered)
                return 0;

        status = acpi_remove_address_space_handler(ACPI_ROOT_OBJECT,
                AML_NFW_SPACE, aml_nfw_handler);
        if (ACPI_FAILURE(status))
                return -ENODEV;

        global_handler_registered = 0;
        printk(KERN_INFO "Global 0x%02X opregion handler removed\n",
                AML_NFW_SPACE);
        return 0;
}

static int aml_nfw_add(struct acpi_device *device)
{
        /*
         * We would normally allocate a new context structure and install
         * the address space handler for the specific device we found.
         * But the HP-UX implementation shares a single global context
         * and always puts the handler at the root, so we'll do the same.
         */
        return aml_nfw_add_global_handler();
}

static int aml_nfw_remove(struct acpi_device *device)
{
        return aml_nfw_remove_global_handler();
}

static const struct acpi_device_id aml_nfw_ids[] = {
        {"HPQ5001", 0},
        {"", 0}
};

static struct acpi_driver acpi_aml_nfw_driver = {
        .name = "native firmware",
        .ids = aml_nfw_ids,
        .ops = {
                .add = aml_nfw_add,
                .remove = aml_nfw_remove,
                },
};

static int __init aml_nfw_init(void)
{
        int result;

        if (force_register)
                aml_nfw_add_global_handler();

        result = acpi_bus_register_driver(&acpi_aml_nfw_driver);
        if (result < 0) {
                aml_nfw_remove_global_handler();
                return result;
        }

        return 0;
}

static void __exit aml_nfw_exit(void)
{
        acpi_bus_unregister_driver(&acpi_aml_nfw_driver);
        aml_nfw_remove_global_handler();
}

module_init(aml_nfw_init);
module_exit(aml_nfw_exit);