// SPDX-License-Identifier: GPL-2.0
/*
 * Intel Speed Select Interface: Mbox via MSR Interface
 * Copyright (c) 2019, Intel Corporation.
 * All rights reserved.
 *
 * Author: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
 */

#include <linux/module.h>
#include <linux/cpuhotplug.h>
#include <linux/pci.h>
#include <linux/sched/signal.h>
#include <linux/slab.h>
#include <linux/suspend.h>
#include <linux/topology.h>
#include <linux/uaccess.h>
#include <uapi/linux/isst_if.h>
#include <asm/cpu_device_id.h>
#include <asm/intel-family.h>
#include <asm/msr.h>

#include "isst_if_common.h"

#define MSR_OS_MAILBOX_BUSY_BIT         31

/*
 * Based on experiments count is never more than 1, as the MSR overhead
 * is enough to finish the command. So here this is the worst case number.
 */
#define OS_MAILBOX_RETRY_COUNT          3

static int isst_if_send_mbox_cmd(u8 command, u8 sub_command, u32 parameter,
                                 u32 command_data, u32 *response_data)
{
        u32 retries;
        u64 data;
        int ret;

        /* Poll for rb bit == 0 */
        retries = OS_MAILBOX_RETRY_COUNT;
        do {
                rdmsrq(MSR_OS_MAILBOX_INTERFACE, data);
                if (data & BIT_ULL(MSR_OS_MAILBOX_BUSY_BIT)) {
                        ret = -EBUSY;
                        continue;
                }
                ret = 0;
                break;
        } while (--retries);

        if (ret)
                return ret;

        /* Write DATA register */
        wrmsrq(MSR_OS_MAILBOX_DATA, command_data);

        /* Write command register */
        data = BIT_ULL(MSR_OS_MAILBOX_BUSY_BIT) |
                      (parameter & GENMASK_ULL(13, 0)) << 16 |
                      (sub_command << 8) |
                      command;
        wrmsrq(MSR_OS_MAILBOX_INTERFACE, data);

        /* Poll for rb bit == 0 */
        retries = OS_MAILBOX_RETRY_COUNT;
        do {
                rdmsrq(MSR_OS_MAILBOX_INTERFACE, data);
                if (data & BIT_ULL(MSR_OS_MAILBOX_BUSY_BIT)) {
                        ret = -EBUSY;
                        continue;
                }

                if (data & 0xff)
                        return -ENXIO;

                if (response_data) {
                        rdmsrq(MSR_OS_MAILBOX_DATA, data);
                        *response_data = data;
                }
                ret = 0;
                break;
        } while (--retries);

        return ret;
}

struct msrl_action {
        int err;
        struct isst_if_mbox_cmd *mbox_cmd;
};

/* revisit, smp_call_function_single should be enough for atomic mailbox! */
static void msrl_update_func(void *info)
{
        struct msrl_action *act = info;

        act->err = isst_if_send_mbox_cmd(act->mbox_cmd->command,
                                         act->mbox_cmd->sub_command,
                                         act->mbox_cmd->parameter,
                                         act->mbox_cmd->req_data,
                                         &act->mbox_cmd->resp_data);
}

static long isst_if_mbox_proc_cmd(u8 *cmd_ptr, int *write_only, int resume)
{
        struct msrl_action action;
        int ret;

        action.mbox_cmd = (struct isst_if_mbox_cmd *)cmd_ptr;

        if (isst_if_mbox_cmd_invalid(action.mbox_cmd))
                return -EINVAL;

        if (isst_if_mbox_cmd_set_req(action.mbox_cmd) &&
            !capable(CAP_SYS_ADMIN))
                return -EPERM;

        /*
         * To complete mailbox command, we need to access two MSRs.
         * So we don't want race to complete a mailbox transcation.
         * Here smp_call ensures that msrl_update_func() has no race
         * and also with wait flag, wait for completion.
         * smp_call_function_single is using get_cpu() and put_cpu().
         */
        ret = smp_call_function_single(action.mbox_cmd->logical_cpu,
                                       msrl_update_func, &action, 1);
        if (ret)
                return ret;

        if (!action.err && !resume && isst_if_mbox_cmd_set_req(action.mbox_cmd))
                action.err = isst_store_cmd(action.mbox_cmd->command,
                                            action.mbox_cmd->sub_command,
                                            action.mbox_cmd->logical_cpu, 1,
                                            action.mbox_cmd->parameter,
                                            action.mbox_cmd->req_data);
        *write_only = 0;

        return action.err;
}


static int isst_pm_notify(struct notifier_block *nb,
                               unsigned long mode, void *_unused)
{
        switch (mode) {
        case PM_POST_HIBERNATION:
        case PM_POST_RESTORE:
        case PM_POST_SUSPEND:
                isst_resume_common();
                break;
        default:
                break;
        }
        return 0;
}

static struct notifier_block isst_pm_nb = {
        .notifier_call = isst_pm_notify,
};

static const struct x86_cpu_id isst_if_cpu_ids[] = {
        X86_MATCH_VFM(INTEL_SKYLAKE_X, NULL),
        {}
};
MODULE_DEVICE_TABLE(x86cpu, isst_if_cpu_ids);

static int __init isst_if_mbox_init(void)
{
        struct isst_if_cmd_cb cb;
        const struct x86_cpu_id *id;
        u64 data;
        int ret;

        id = x86_match_cpu(isst_if_cpu_ids);
        if (!id)
                return -ENODEV;

        /* Check presence of mailbox MSRs */
        ret = rdmsrq_safe(MSR_OS_MAILBOX_INTERFACE, &data);
        if (ret)
                return ret;

        ret = rdmsrq_safe(MSR_OS_MAILBOX_DATA, &data);
        if (ret)
                return ret;

        memset(&cb, 0, sizeof(cb));
        cb.cmd_size = sizeof(struct isst_if_mbox_cmd);
        cb.offset = offsetof(struct isst_if_mbox_cmds, mbox_cmd);
        cb.cmd_callback = isst_if_mbox_proc_cmd;
        cb.owner = THIS_MODULE;
        ret = isst_if_cdev_register(ISST_IF_DEV_MBOX, &cb);
        if (ret)
                return ret;

        ret = register_pm_notifier(&isst_pm_nb);
        if (ret)
                isst_if_cdev_unregister(ISST_IF_DEV_MBOX);

        return ret;
}
module_init(isst_if_mbox_init)

static void __exit isst_if_mbox_exit(void)
{
        unregister_pm_notifier(&isst_pm_nb);
        isst_if_cdev_unregister(ISST_IF_DEV_MBOX);
}
module_exit(isst_if_mbox_exit)

MODULE_LICENSE("GPL v2");
MODULE_DESCRIPTION("Intel speed select interface mailbox driver");