// SPDX-License-Identifier: GPL-2.0
/*
 * UCSI driver for ChromeOS EC
 *
 * Copyright 2024 Google LLC.
 */

#include <linux/container_of.h>
#include <linux/dev_printk.h>
#include <linux/jiffies.h>
#include <linux/mod_devicetable.h>
#include <linux/module.h>
#include <linux/platform_data/cros_ec_commands.h>
#include <linux/platform_data/cros_usbpd_notify.h>
#include <linux/platform_data/cros_ec_proto.h>
#include <linux/platform_device.h>
#include <linux/slab.h>
#include <linux/wait.h>
#include <linux/usb/typec_altmode.h>

#include "ucsi.h"

/*
 * Maximum size in bytes of a UCSI message between AP and EC
 */
#define MAX_EC_DATA_SIZE        256

/*
 * Maximum time in milliseconds the cros_ec_ucsi driver
 * will wait for a response to a command or and ack.
 */
#define WRITE_TMO_MS            5000

/* Number of times to attempt recovery from a write timeout before giving up. */
#define WRITE_TMO_CTR_MAX       5

/* Delay between mode entry/exit attempts, ms */
static const unsigned int mode_selection_delay = 1000;
/* Timeout for a mode entry attempt, ms */
static const unsigned int mode_selection_timeout = 4000;

struct cros_ucsi_data {
        struct device *dev;
        struct ucsi *ucsi;

        struct cros_ec_device *ec;
        struct notifier_block nb;
        struct work_struct work;
        struct delayed_work write_tmo;
        int tmo_counter;

        struct completion complete;
        unsigned long flags;
};

static int cros_ucsi_read(struct ucsi *ucsi, unsigned int offset, void *val,
                          size_t val_len)
{
        struct cros_ucsi_data *udata = ucsi_get_drvdata(ucsi);
        struct ec_params_ucsi_ppm_get req = {
                .offset = offset,
                .size = val_len,
        };
        int ret;

        if (val_len > MAX_EC_DATA_SIZE) {
                dev_err(udata->dev, "Can't read %zu bytes. Too big.\n", val_len);
                return -EINVAL;
        }

        ret = cros_ec_cmd(udata->ec, 0, EC_CMD_UCSI_PPM_GET,
                          &req, sizeof(req), val, val_len);
        if (ret < 0) {
                dev_warn(udata->dev, "Failed to send EC message UCSI_PPM_GET: error=%d\n", ret);
                return ret;
        }
        return 0;
}

static int cros_ucsi_read_version(struct ucsi *ucsi, u16 *version)
{
        return cros_ucsi_read(ucsi, UCSI_VERSION, version, sizeof(*version));
}

static int cros_ucsi_read_cci(struct ucsi *ucsi, u32 *cci)
{
        return cros_ucsi_read(ucsi, UCSI_CCI, cci, sizeof(*cci));
}

static int cros_ucsi_read_message_in(struct ucsi *ucsi, void *val,
                                     size_t val_len)
{
        return cros_ucsi_read(ucsi, UCSI_MESSAGE_IN, val, val_len);
}

static int cros_ucsi_async_control(struct ucsi *ucsi, u64 cmd)
{
        struct cros_ucsi_data *udata = ucsi_get_drvdata(ucsi);
        u8 ec_buf[sizeof(struct ec_params_ucsi_ppm_set) + sizeof(cmd)];
        struct ec_params_ucsi_ppm_set *req = (struct ec_params_ucsi_ppm_set *) ec_buf;
        int ret;

        req->offset = UCSI_CONTROL;
        memcpy(req->data, &cmd, sizeof(cmd));
        ret = cros_ec_cmd(udata->ec, 0, EC_CMD_UCSI_PPM_SET,
                          req, sizeof(ec_buf), NULL, 0);
        if (ret < 0) {
                dev_warn(udata->dev, "Failed to send EC message UCSI_PPM_SET: error=%d\n", ret);
                return ret;
        }
        return 0;
}

static int cros_ucsi_sync_control(struct ucsi *ucsi, u64 cmd, u32 *cci,
                                  void *data, size_t size)
{
        struct cros_ucsi_data *udata = ucsi_get_drvdata(ucsi);
        int ret;

        ret = ucsi_sync_control_common(ucsi, cmd, cci, data, size);
        switch (ret) {
        case -EBUSY:
                /* EC may return -EBUSY if CCI.busy is set.
                 * Convert this to a timeout.
                 */
        case -ETIMEDOUT:
                /* Schedule recovery attempt when we timeout
                 * or tried to send a command while still busy.
                 */
                cancel_delayed_work_sync(&udata->write_tmo);
                schedule_delayed_work(&udata->write_tmo,
                                      msecs_to_jiffies(WRITE_TMO_MS));
                break;
        case 0:
                /* Successful write. Cancel any pending recovery work. */
                cancel_delayed_work_sync(&udata->write_tmo);
                break;
        }

        return ret;
}

static void cros_ucsi_add_partner_altmodes(struct ucsi_connector *con)
{
        if (!con->typec_cap.no_mode_control)
                typec_mode_selection_start(con->partner,
                                           mode_selection_delay,
                                           mode_selection_timeout);
}

static void cros_ucsi_remove_partner_altmodes(struct ucsi_connector *con)
{
        if (!con->typec_cap.no_mode_control)
                typec_mode_selection_delete(con->partner);
}

static const struct ucsi_operations cros_ucsi_ops = {
        .read_version = cros_ucsi_read_version,
        .read_cci = cros_ucsi_read_cci,
        .poll_cci = cros_ucsi_read_cci,
        .read_message_in = cros_ucsi_read_message_in,
        .async_control = cros_ucsi_async_control,
        .sync_control = cros_ucsi_sync_control,
        .add_partner_altmodes = cros_ucsi_add_partner_altmodes,
        .remove_partner_altmodes = cros_ucsi_remove_partner_altmodes,
};

static void cros_ucsi_work(struct work_struct *work)
{
        struct cros_ucsi_data *udata = container_of(work, struct cros_ucsi_data, work);
        u32 cci;

        if (cros_ucsi_read_cci(udata->ucsi, &cci))
                return;

        ucsi_notify_common(udata->ucsi, cci);
}

static void cros_ucsi_write_timeout(struct work_struct *work)
{
        struct cros_ucsi_data *udata =
                container_of(work, struct cros_ucsi_data, write_tmo.work);
        u32 cci;
        u64 cmd;

        if (cros_ucsi_read(udata->ucsi, UCSI_CCI, &cci, sizeof(cci))) {
                dev_err(udata->dev,
                        "Reading CCI failed; no write timeout recovery possible.\n");
                return;
        }

        if (cci & UCSI_CCI_BUSY) {
                udata->tmo_counter++;

                if (udata->tmo_counter <= WRITE_TMO_CTR_MAX)
                        schedule_delayed_work(&udata->write_tmo,
                                              msecs_to_jiffies(WRITE_TMO_MS));
                else
                        dev_err(udata->dev,
                                "PPM unresponsive - too many write timeouts.\n");

                return;
        }

        /* No longer busy means we can reset our timeout counter. */
        udata->tmo_counter = 0;

        /* Need to ack previous command which may have timed out. */
        if (cci & UCSI_CCI_COMMAND_COMPLETE) {
                cmd = UCSI_ACK_CC_CI | UCSI_ACK_COMMAND_COMPLETE;
                cros_ucsi_async_control(udata->ucsi, cmd);

                /* Check again after a few seconds that the system has
                 * recovered to make sure our async write above was successful.
                 */
                schedule_delayed_work(&udata->write_tmo,
                                      msecs_to_jiffies(WRITE_TMO_MS));
                return;
        }

        /* We recovered from a previous timeout. Treat this as a recovery from
         * suspend and call resume.
         */
        ucsi_resume(udata->ucsi);
}

static int cros_ucsi_event(struct notifier_block *nb,
                           unsigned long host_event, void *_notify)
{
        struct cros_ucsi_data *udata = container_of(nb, struct cros_ucsi_data, nb);

        if (host_event & PD_EVENT_INIT) {
                /* Late init event received from ChromeOS EC. Treat this as a
                 * system resume to re-enable communication with the PPM.
                 */
                dev_dbg(udata->dev, "Late PD init received\n");
                ucsi_resume(udata->ucsi);
        }

        if (host_event & PD_EVENT_PPM) {
                dev_dbg(udata->dev, "UCSI notification received\n");
                flush_work(&udata->work);
                schedule_work(&udata->work);
        }

        return NOTIFY_OK;
}

static void cros_ucsi_destroy(struct cros_ucsi_data *udata)
{
        cros_usbpd_unregister_notify(&udata->nb);
        cancel_delayed_work_sync(&udata->write_tmo);
        cancel_work_sync(&udata->work);
        ucsi_destroy(udata->ucsi);
}

static int cros_ucsi_probe(struct platform_device *pdev)
{
        struct device *dev = &pdev->dev;
        struct cros_ec_dev *ec_data = dev_get_drvdata(dev->parent);
        struct cros_ucsi_data *udata;
        int ret;

        udata = devm_kzalloc(dev, sizeof(*udata), GFP_KERNEL);
        if (!udata)
                return -ENOMEM;

        udata->dev = dev;

        udata->ec = ec_data->ec_dev;
        if (!udata->ec)
                return dev_err_probe(dev, -ENODEV, "couldn't find parent EC device\n");

        platform_set_drvdata(pdev, udata);

        INIT_WORK(&udata->work, cros_ucsi_work);
        INIT_DELAYED_WORK(&udata->write_tmo, cros_ucsi_write_timeout);
        init_completion(&udata->complete);

        udata->ucsi = ucsi_create(dev, &cros_ucsi_ops);
        if (IS_ERR(udata->ucsi))
                return dev_err_probe(dev, PTR_ERR(udata->ucsi), "failed to allocate UCSI instance\n");

        ucsi_set_drvdata(udata->ucsi, udata);

        udata->nb.notifier_call = cros_ucsi_event;
        ret = cros_usbpd_register_notify(&udata->nb);
        if (ret) {
                dev_err_probe(dev, ret, "failed to register notifier\n");
                ucsi_destroy(udata->ucsi);
                return ret;
        }

        ret = ucsi_register(udata->ucsi);
        if (ret) {
                dev_err_probe(dev, ret, "failed to register UCSI\n");
                cros_ucsi_destroy(udata);
                return ret;
        }

        return 0;
}

static void cros_ucsi_remove(struct platform_device *dev)
{
        struct cros_ucsi_data *udata = platform_get_drvdata(dev);

        ucsi_unregister(udata->ucsi);
        cros_ucsi_destroy(udata);
}

static int __maybe_unused cros_ucsi_suspend(struct device *dev)
{
        struct cros_ucsi_data *udata = dev_get_drvdata(dev);

        cancel_delayed_work_sync(&udata->write_tmo);
        cancel_work_sync(&udata->work);

        return 0;
}

static void __maybe_unused cros_ucsi_complete(struct device *dev)
{
        struct cros_ucsi_data *udata = dev_get_drvdata(dev);

        ucsi_resume(udata->ucsi);
}

/*
 * UCSI protocol is also used on ChromeOS platforms which reply on
 * cros_ec_lpc.c driver for communication with embedded controller (EC).
 * On such platforms communication with the EC is not available until
 * the .complete() callback of the cros_ec_lpc driver is executed.
 * For this reason we delay ucsi_resume() until the .complete() stage
 * otherwise UCSI SET_NOTIFICATION_ENABLE command will fail and we won't
 * receive any UCSI notifications from the EC where PPM is implemented.
 */
static const struct dev_pm_ops cros_ucsi_pm_ops = {
#ifdef CONFIG_PM_SLEEP
        .suspend = cros_ucsi_suspend,
        .complete = cros_ucsi_complete,
#endif
};

static const struct platform_device_id cros_ucsi_id[] = {
        { KBUILD_MODNAME, 0 },
        {}
};
MODULE_DEVICE_TABLE(platform, cros_ucsi_id);

static struct platform_driver cros_ucsi_driver = {
        .driver = {
                .name = KBUILD_MODNAME,
                .pm = &cros_ucsi_pm_ops,
        },
        .id_table = cros_ucsi_id,
        .probe = cros_ucsi_probe,
        .remove = cros_ucsi_remove,
};

module_platform_driver(cros_ucsi_driver);

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("UCSI driver for ChromeOS EC");