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

#include <linux/cpufeature.h>
#include <linux/module.h>
#include <linux/pci.h>
#include <linux/sched/signal.h>
#include <linux/uaccess.h>
#include <uapi/linux/isst_if.h>

#include "isst_if_common.h"

#define PUNIT_MAILBOX_DATA              0xA0
#define PUNIT_MAILBOX_INTERFACE         0xA4
#define PUNIT_MAILBOX_BUSY_BIT          31

/*
 * The average time to complete mailbox commands is less than 40us. Most of
 * the commands complete in few micro seconds. But the same firmware handles
 * requests from all power management features.
 * We can create a scenario where we flood the firmware with requests then
 * the mailbox response can be delayed for 100s of micro seconds. So define
 * two timeouts. One for average case and one for long.
 * If the firmware is taking more than average, just call cond_resched().
 */
#define OS_MAILBOX_TIMEOUT_AVG_US       40
#define OS_MAILBOX_TIMEOUT_MAX_US       1000

struct isst_if_device {
        struct mutex mutex;
};

static int isst_if_mbox_cmd(struct pci_dev *pdev,
                            struct isst_if_mbox_cmd *mbox_cmd)
{
        s64 tm_delta = 0;
        ktime_t tm;
        u32 data;
        int ret;

        /* Poll for rb bit == 0 */
        tm = ktime_get();
        do {
                ret = pci_read_config_dword(pdev, PUNIT_MAILBOX_INTERFACE,
                                            &data);
                if (ret)
                        return ret;

                if (data & BIT_ULL(PUNIT_MAILBOX_BUSY_BIT)) {
                        ret = -EBUSY;
                        tm_delta = ktime_us_delta(ktime_get(), tm);
                        if (tm_delta > OS_MAILBOX_TIMEOUT_AVG_US)
                                cond_resched();
                        continue;
                }
                ret = 0;
                break;
        } while (tm_delta < OS_MAILBOX_TIMEOUT_MAX_US);

        if (ret)
                return ret;

        /* Write DATA register */
        ret = pci_write_config_dword(pdev, PUNIT_MAILBOX_DATA,
                                     mbox_cmd->req_data);
        if (ret)
                return ret;

        /* Write command register */
        data = BIT_ULL(PUNIT_MAILBOX_BUSY_BIT) |
                      (mbox_cmd->parameter & GENMASK_ULL(13, 0)) << 16 |
                      (mbox_cmd->sub_command << 8) |
                      mbox_cmd->command;

        ret = pci_write_config_dword(pdev, PUNIT_MAILBOX_INTERFACE, data);
        if (ret)
                return ret;

        /* Poll for rb bit == 0 */
        tm_delta = 0;
        tm = ktime_get();
        do {
                ret = pci_read_config_dword(pdev, PUNIT_MAILBOX_INTERFACE,
                                            &data);
                if (ret)
                        return ret;

                if (data & BIT_ULL(PUNIT_MAILBOX_BUSY_BIT)) {
                        ret = -EBUSY;
                        tm_delta = ktime_us_delta(ktime_get(), tm);
                        if (tm_delta > OS_MAILBOX_TIMEOUT_AVG_US)
                                cond_resched();
                        continue;
                }

                if (data & 0xff)
                        return -ENXIO;

                ret = pci_read_config_dword(pdev, PUNIT_MAILBOX_DATA, &data);
                if (ret)
                        return ret;

                mbox_cmd->resp_data = data;
                ret = 0;
                break;
        } while (tm_delta < OS_MAILBOX_TIMEOUT_MAX_US);

        return ret;
}

static long isst_if_mbox_proc_cmd(u8 *cmd_ptr, int *write_only, int resume)
{
        struct isst_if_mbox_cmd *mbox_cmd;
        struct isst_if_device *punit_dev;
        struct pci_dev *pdev;
        int ret;

        mbox_cmd = (struct isst_if_mbox_cmd *)cmd_ptr;

        if (isst_if_mbox_cmd_invalid(mbox_cmd))
                return -EINVAL;

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

        pdev = isst_if_get_pci_dev(mbox_cmd->logical_cpu, 1, 30, 1);
        if (!pdev)
                return -EINVAL;

        punit_dev = pci_get_drvdata(pdev);
        if (!punit_dev)
                return -EINVAL;

        /*
         * Basically we are allowing one complete mailbox transaction on
         * a mapped PCI device at a time.
         */
        mutex_lock(&punit_dev->mutex);
        ret = isst_if_mbox_cmd(pdev, mbox_cmd);
        if (!ret && !resume && isst_if_mbox_cmd_set_req(mbox_cmd))
                ret = isst_store_cmd(mbox_cmd->command,
                                     mbox_cmd->sub_command,
                                     mbox_cmd->logical_cpu, 1,
                                     mbox_cmd->parameter,
                                     mbox_cmd->req_data);
        mutex_unlock(&punit_dev->mutex);
        if (ret)
                return ret;

        *write_only = 0;

        return 0;
}

static const struct pci_device_id isst_if_mbox_ids[] = {
        { PCI_VDEVICE(INTEL, PCI_DEVICE_ID_INTEL_CFG_MBOX_DEVID_0)},
        { PCI_VDEVICE(INTEL, PCI_DEVICE_ID_INTEL_CFG_MBOX_DEVID_1)},
        { 0 },
};
MODULE_DEVICE_TABLE(pci, isst_if_mbox_ids);

static int isst_if_mbox_probe(struct pci_dev *pdev,
                              const struct pci_device_id *ent)
{
        struct isst_if_device *punit_dev;
        struct isst_if_cmd_cb cb;
        int ret;

        punit_dev = devm_kzalloc(&pdev->dev, sizeof(*punit_dev), GFP_KERNEL);
        if (!punit_dev)
                return -ENOMEM;

        ret = pcim_enable_device(pdev);
        if (ret)
                return ret;

        mutex_init(&punit_dev->mutex);
        pci_set_drvdata(pdev, punit_dev);

        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)
                mutex_destroy(&punit_dev->mutex);

        return ret;
}

static void isst_if_mbox_remove(struct pci_dev *pdev)
{
        struct isst_if_device *punit_dev;

        punit_dev = pci_get_drvdata(pdev);
        isst_if_cdev_unregister(ISST_IF_DEV_MBOX);
        mutex_destroy(&punit_dev->mutex);
}

static int __maybe_unused isst_if_resume(struct device *device)
{
        isst_resume_common();
        return 0;
}

static SIMPLE_DEV_PM_OPS(isst_if_pm_ops, NULL, isst_if_resume);

static struct pci_driver isst_if_pci_driver = {
        .name                   = "isst_if_mbox_pci",
        .id_table               = isst_if_mbox_ids,
        .probe                  = isst_if_mbox_probe,
        .remove                 = isst_if_mbox_remove,
        .driver.pm              = &isst_if_pm_ops,
};

module_pci_driver(isst_if_pci_driver);

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