aml_nfw.c

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/*
 * OpRegion handler to allow AML to call native firmware
 *
 * (c) Copyright 2007 Hewlett-Packard Development Company, L.P.
 *  Bjorn Helgaas <[email protected]>
 *
 * 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 <acpi/acpi_bus.h>
#include <acpi/acpi_drivers.h>
#include <asm/sal.h>

MODULE_AUTHOR("Bjorn Helgaas <[email protected]>");
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, int type)
{
    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);