// SPDX-License-Identifier: GPL-2.0-only
/*
 *  SMI methods for use with dell-smbios
 *
 *  Copyright (c) Red Hat <mjg@redhat.com>
 *  Copyright (c) 2014 Gabriele Mazzotta <gabriele.mzt@gmail.com>
 *  Copyright (c) 2014 Pali Rohár <pali@kernel.org>
 *  Copyright (c) 2017 Dell Inc.
 */
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/dmi.h>
#include <linux/gfp.h>
#include <linux/io.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/platform_device.h>
#include "dcdbas.h"
#include "dell-smbios.h"

static int da_command_address;
static int da_command_code;
static struct smi_buffer smi_buf;
static struct calling_interface_buffer *buffer;
static struct platform_device *platform_device;
static DEFINE_MUTEX(smm_mutex);

static void parse_da_table(const struct dmi_header *dm)
{
        struct calling_interface_structure *table =
                container_of(dm, struct calling_interface_structure, header);

        /* 4 bytes of table header, plus 7 bytes of Dell header, plus at least
         * 6 bytes of entry
         */
        if (dm->length < 17)
                return;

        da_command_address = table->cmdIOAddress;
        da_command_code = table->cmdIOCode;
}

static void find_cmd_address(const struct dmi_header *dm, void *dummy)
{
        switch (dm->type) {
        case 0xda: /* Calling interface */
                parse_da_table(dm);
                break;
        }
}

static int dell_smbios_smm_call(struct calling_interface_buffer *input)
{
        struct smi_cmd command;
        size_t size;

        size = sizeof(struct calling_interface_buffer);
        command.magic = SMI_CMD_MAGIC;
        command.command_address = da_command_address;
        command.command_code = da_command_code;
        command.ebx = smi_buf.dma;
        command.ecx = 0x42534931;

        mutex_lock(&smm_mutex);
        memcpy(buffer, input, size);
        dcdbas_smi_request(&command);
        memcpy(input, buffer, size);
        mutex_unlock(&smm_mutex);
        return 0;
}

/* When enabled this indicates that SMM won't work */
static bool test_wsmt_enabled(void)
{
        struct calling_interface_token *wsmt;

        /* if token doesn't exist, SMM will work */
        wsmt = dell_smbios_find_token(WSMT_EN_TOKEN);
        if (!wsmt)
                return false;

        /* If token exists, try to access over SMM but set a dummy return.
         * - If WSMT disabled it will be overwritten by SMM
         * - If WSMT enabled then dummy value will remain
         */
        buffer->cmd_class = CLASS_TOKEN_READ;
        buffer->cmd_select = SELECT_TOKEN_STD;
        memset(buffer, 0, sizeof(struct calling_interface_buffer));
        buffer->input[0] = wsmt->location;
        buffer->output[0] = 99;
        dell_smbios_smm_call(buffer);
        if (buffer->output[0] == 99)
                return true;

        return false;
}

int init_dell_smbios_smm(void)
{
        int ret;
        /*
         * Allocate buffer below 4GB for SMI data--only 32-bit physical addr
         * is passed to SMI handler.
         */
        ret = dcdbas_smi_alloc(&smi_buf, PAGE_SIZE);
        if (ret)
                return ret;
        buffer = (void *)smi_buf.virt;

        dmi_walk(find_cmd_address, NULL);

        if (test_wsmt_enabled()) {
                pr_debug("Disabling due to WSMT enabled\n");
                ret = -ENODEV;
                goto fail_wsmt;
        }

        platform_device = platform_device_alloc("dell-smbios", 1);
        if (!platform_device) {
                ret = -ENOMEM;
                goto fail_platform_device_alloc;
        }

        ret = platform_device_add(platform_device);
        if (ret)
                goto fail_platform_device_add;

        ret = dell_smbios_register_device(&platform_device->dev, 0, &dell_smbios_smm_call);
        if (ret)
                goto fail_register;

        return 0;

fail_register:
        platform_device_del(platform_device);

fail_platform_device_add:
        platform_device_put(platform_device);

fail_wsmt:
fail_platform_device_alloc:
        dcdbas_smi_free(&smi_buf);
        return ret;
}

void exit_dell_smbios_smm(void)
{
        if (platform_device) {
                dell_smbios_unregister_device(&platform_device->dev);
                platform_device_unregister(platform_device);
                dcdbas_smi_free(&smi_buf);
        }
}