WIP FPC-III support

[linux/fpc-iii.git] / drivers / platform / chrome / cros_ec_ishtp.c

// SPDX-License-Identifier: GPL-2.0
// ISHTP interface for ChromeOS Embedded Controller
//
// Copyright (c) 2019, Intel Corporation.
//
// ISHTP client driver for talking to the Chrome OS EC firmware running
// on Intel Integrated Sensor Hub (ISH) using the ISH Transport protocol
// (ISH-TP).

#include <linux/delay.h>
#include <linux/module.h>
#include <linux/pci.h>
#include <linux/platform_data/cros_ec_commands.h>
#include <linux/platform_data/cros_ec_proto.h>
#include <linux/intel-ish-client-if.h>

#include "cros_ec.h"

/*
 * ISH TX/RX ring buffer pool size
 *
 * The AP->ISH messages and corresponding ISH->AP responses are
 * serialized. We need 1 TX and 1 RX buffer for these.
 *
 * The MKBP ISH->AP events are serialized. We need one additional RX
 * buffer for them.
 */
#define CROS_ISH_CL_TX_RING_SIZE                8
#define CROS_ISH_CL_RX_RING_SIZE                8

/* ISH CrOS EC Host Commands */
enum cros_ec_ish_channel {
        CROS_EC_COMMAND = 1,                    /* AP->ISH message */
        CROS_MKBP_EVENT = 2,                    /* ISH->AP events */
};

/*
 * ISH firmware timeout for 1 message send failure is 1Hz, and the
 * firmware will retry 2 times, so 3Hz is used for timeout.
 */
#define ISHTP_SEND_TIMEOUT                      (3 * HZ)

/* ISH Transport CrOS EC ISH client unique GUID */
static const guid_t cros_ish_guid =
        GUID_INIT(0x7b7154d0, 0x56f4, 0x4bdc,
                  0xb0, 0xd8, 0x9e, 0x7c, 0xda, 0xe0, 0xd6, 0xa0);

struct header {
        u8 channel;
        u8 status;
        u8 token;
        u8 reserved;
} __packed;

struct cros_ish_out_msg {
        struct header hdr;
        struct ec_host_request ec_request;
} __packed;

struct cros_ish_in_msg {
        struct header hdr;
        struct ec_host_response ec_response;
} __packed;

#define IN_MSG_EC_RESPONSE_PREAMBLE                                     \
        offsetof(struct cros_ish_in_msg, ec_response)

#define OUT_MSG_EC_REQUEST_PREAMBLE                                     \
        offsetof(struct cros_ish_out_msg, ec_request)

#define cl_data_to_dev(client_data) ishtp_device((client_data)->cl_device)

/*
 * The Read-Write Semaphore is used to prevent message TX or RX while
 * the ishtp client is being initialized or undergoing reset.
 *
 * The readers are the kernel function calls responsible for IA->ISH
 * and ISH->AP messaging.
 *
 * The writers are .reset() and .probe() function.
 */
static DECLARE_RWSEM(init_lock);

/**
 * struct response_info - Encapsulate firmware response related
 * information for passing between function ish_send() and
 * process_recv() callback.
 *
 * @data: Copy the data received from firmware here.
 * @max_size: Max size allocated for the @data buffer. If the received
 * data exceeds this value, we log an error.
 * @size: Actual size of data received from firmware.
 * @error: 0 for success, negative error code for a failure in process_recv().
 * @token: Expected token for response that we are waiting on.
 * @received: Set to true on receiving a valid firmware response to host command
 * @wait_queue: Wait queue for host to wait for firmware response.
 */
struct response_info {
        void *data;
        size_t max_size;
        size_t size;
        int error;
        u8 token;
        bool received;
        wait_queue_head_t wait_queue;
};

/**
 * struct ishtp_cl_data - Encapsulate per ISH TP Client.
 *
 * @cros_ish_cl: ISHTP firmware client instance.
 * @cl_device: ISHTP client device instance.
 * @response: Response info passing between ish_send() and process_recv().
 * @work_ishtp_reset: Work queue reset handling.
 * @work_ec_evt: Work queue for EC events.
 * @ec_dev: CrOS EC MFD device.
 *
 * This structure is used to store per client data.
 */
struct ishtp_cl_data {
        struct ishtp_cl *cros_ish_cl;
        struct ishtp_cl_device *cl_device;

        /*
         * Used for passing firmware response information between
         * ish_send() and process_recv() callback.
         */
        struct response_info response;

        struct work_struct work_ishtp_reset;
        struct work_struct work_ec_evt;
        struct cros_ec_device *ec_dev;
};

/**
 * ish_evt_handler - ISH to AP event handler
 * @work: Work struct
 */
static void ish_evt_handler(struct work_struct *work)
{
        struct ishtp_cl_data *client_data =
                container_of(work, struct ishtp_cl_data, work_ec_evt);
        struct cros_ec_device *ec_dev = client_data->ec_dev;
        bool ec_has_more_events;

        do {
                ec_has_more_events = cros_ec_handle_event(ec_dev);
        } while (ec_has_more_events);
}

/**
 * ish_send() - Send message from host to firmware
 *
 * @client_data: Client data instance
 * @out_msg: Message buffer to be sent to firmware
 * @out_size: Size of out going message
 * @in_msg: Message buffer where the incoming data is copied. This buffer
 * is allocated by calling
 * @in_size: Max size of incoming message
 *
 * Return: Number of bytes copied in the in_msg on success, negative
 * error code on failure.
 */
static int ish_send(struct ishtp_cl_data *client_data,
                    u8 *out_msg, size_t out_size,
                    u8 *in_msg, size_t in_size)
{
        static u8 next_token;
        int rv;
        struct header *out_hdr = (struct header *)out_msg;
        struct ishtp_cl *cros_ish_cl = client_data->cros_ish_cl;

        dev_dbg(cl_data_to_dev(client_data),
                "%s: channel=%02u status=%02u\n",
                __func__, out_hdr->channel, out_hdr->status);

        /* Setup for incoming response */
        client_data->response.data = in_msg;
        client_data->response.max_size = in_size;
        client_data->response.error = 0;
        client_data->response.token = next_token++;
        client_data->response.received = false;

        out_hdr->token = client_data->response.token;

        rv = ishtp_cl_send(cros_ish_cl, out_msg, out_size);
        if (rv) {
                dev_err(cl_data_to_dev(client_data),
                        "ishtp_cl_send error %d\n", rv);
                return rv;
        }

        wait_event_interruptible_timeout(client_data->response.wait_queue,
                                         client_data->response.received,
                                         ISHTP_SEND_TIMEOUT);
        if (!client_data->response.received) {
                dev_err(cl_data_to_dev(client_data),
                        "Timed out for response to host message\n");
                return -ETIMEDOUT;
        }

        if (client_data->response.error < 0)
                return client_data->response.error;

        return client_data->response.size;
}

/**
 * process_recv() - Received and parse incoming packet
 * @cros_ish_cl: Client instance to get stats
 * @rb_in_proc: Host interface message buffer
 * @timestamp: Timestamp of when parent callback started
 *
 * Parse the incoming packet. If it is a response packet then it will
 * update per instance flags and wake up the caller waiting to for the
 * response. If it is an event packet then it will schedule event work.
 */
static void process_recv(struct ishtp_cl *cros_ish_cl,
                         struct ishtp_cl_rb *rb_in_proc, ktime_t timestamp)
{
        size_t data_len = rb_in_proc->buf_idx;
        struct ishtp_cl_data *client_data =
                ishtp_get_client_data(cros_ish_cl);
        struct device *dev = cl_data_to_dev(client_data);
        struct cros_ish_in_msg *in_msg =
                (struct cros_ish_in_msg *)rb_in_proc->buffer.data;

        /* Proceed only if reset or init is not in progress */
        if (!down_read_trylock(&init_lock)) {
                /* Free the buffer */
                ishtp_cl_io_rb_recycle(rb_in_proc);
                dev_warn(dev,
                         "Host is not ready to receive incoming messages\n");
                return;
        }

        /*
         * All firmware messages contain a header. Check the buffer size
         * before accessing elements inside.
         */
        if (!rb_in_proc->buffer.data) {
                dev_warn(dev, "rb_in_proc->buffer.data returned null");
                client_data->response.error = -EBADMSG;
                goto end_error;
        }

        if (data_len < sizeof(struct header)) {
                dev_err(dev, "data size %zu is less than header %zu\n",
                        data_len, sizeof(struct header));
                client_data->response.error = -EMSGSIZE;
                goto end_error;
        }

        dev_dbg(dev, "channel=%02u status=%02u\n",
                in_msg->hdr.channel, in_msg->hdr.status);

        switch (in_msg->hdr.channel) {
        case CROS_EC_COMMAND:
                if (client_data->response.received) {
                        dev_err(dev,
                                "Previous firmware message not yet processed\n");
                        goto end_error;
                }

                if (client_data->response.token != in_msg->hdr.token) {
                        dev_err_ratelimited(dev,
                                            "Dropping old response token %d\n",
                                            in_msg->hdr.token);
                        goto end_error;
                }

                /* Sanity check */
                if (!client_data->response.data) {
                        dev_err(dev,
                                "Receiving buffer is null. Should be allocated by calling function\n");
                        client_data->response.error = -EINVAL;
                        goto error_wake_up;
                }

                if (data_len > client_data->response.max_size) {
                        dev_err(dev,
                                "Received buffer size %zu is larger than allocated buffer %zu\n",
                                data_len, client_data->response.max_size);
                        client_data->response.error = -EMSGSIZE;
                        goto error_wake_up;
                }

                if (in_msg->hdr.status) {
                        dev_err(dev, "firmware returned status %d\n",
                                in_msg->hdr.status);
                        client_data->response.error = -EIO;
                        goto error_wake_up;
                }

                /* Update the actual received buffer size */
                client_data->response.size = data_len;

                /*
                 * Copy the buffer received in firmware response for the
                 * calling thread.
                 */
                memcpy(client_data->response.data,
                       rb_in_proc->buffer.data, data_len);

error_wake_up:
                /* Free the buffer since we copied data or didn't need it */
                ishtp_cl_io_rb_recycle(rb_in_proc);
                rb_in_proc = NULL;

                /* Set flag before waking up the caller */
                client_data->response.received = true;

                /* Wake the calling thread */
                wake_up_interruptible(&client_data->response.wait_queue);

                break;

        case CROS_MKBP_EVENT:
                /* Free the buffer. This is just an event without data */
                ishtp_cl_io_rb_recycle(rb_in_proc);
                rb_in_proc = NULL;
                /*
                 * Set timestamp from beginning of function since we actually
                 * got an incoming MKBP event
                 */
                client_data->ec_dev->last_event_time = timestamp;
                schedule_work(&client_data->work_ec_evt);

                break;

        default:
                dev_err(dev, "Invalid channel=%02d\n", in_msg->hdr.channel);
        }

end_error:
        /* Free the buffer if we already haven't */
        if (rb_in_proc)
                ishtp_cl_io_rb_recycle(rb_in_proc);

        up_read(&init_lock);
}

/**
 * ish_event_cb() - bus driver callback for incoming message
 * @cl_device: ISHTP client device for which this message is targeted.
 *
 * Remove the packet from the list and process the message by calling
 * process_recv.
 */
static void ish_event_cb(struct ishtp_cl_device *cl_device)
{
        struct ishtp_cl_rb *rb_in_proc;
        struct ishtp_cl *cros_ish_cl = ishtp_get_drvdata(cl_device);
        ktime_t timestamp;

        /*
         * Take timestamp as close to hardware interrupt as possible for sensor
         * timestamps.
         */
        timestamp = cros_ec_get_time_ns();

        while ((rb_in_proc = ishtp_cl_rx_get_rb(cros_ish_cl)) != NULL) {
                /* Decide what to do with received data */
                process_recv(cros_ish_cl, rb_in_proc, timestamp);
        }
}

/**
 * cros_ish_init() - Init function for ISHTP client
 * @cros_ish_cl: ISHTP client instance
 *
 * This function complete the initializtion of the client.
 *
 * Return: 0 for success, negative error code for failure.
 */
static int cros_ish_init(struct ishtp_cl *cros_ish_cl)
{
        int rv;
        struct ishtp_device *dev;
        struct ishtp_fw_client *fw_client;
        struct ishtp_cl_data *client_data = ishtp_get_client_data(cros_ish_cl);

        rv = ishtp_cl_link(cros_ish_cl);
        if (rv) {
                dev_err(cl_data_to_dev(client_data),
                        "ishtp_cl_link failed\n");
                return rv;
        }

        dev = ishtp_get_ishtp_device(cros_ish_cl);

        /* Connect to firmware client */
        ishtp_set_tx_ring_size(cros_ish_cl, CROS_ISH_CL_TX_RING_SIZE);
        ishtp_set_rx_ring_size(cros_ish_cl, CROS_ISH_CL_RX_RING_SIZE);

        fw_client = ishtp_fw_cl_get_client(dev, &cros_ish_guid);
        if (!fw_client) {
                dev_err(cl_data_to_dev(client_data),
                        "ish client uuid not found\n");
                rv = -ENOENT;
                goto err_cl_unlink;
        }

        ishtp_cl_set_fw_client_id(cros_ish_cl,
                                  ishtp_get_fw_client_id(fw_client));
        ishtp_set_connection_state(cros_ish_cl, ISHTP_CL_CONNECTING);

        rv = ishtp_cl_connect(cros_ish_cl);
        if (rv) {
                dev_err(cl_data_to_dev(client_data),
                        "client connect fail\n");
                goto err_cl_unlink;
        }

        ishtp_register_event_cb(client_data->cl_device, ish_event_cb);
        return 0;

err_cl_unlink:
        ishtp_cl_unlink(cros_ish_cl);
        return rv;
}

/**
 * cros_ish_deinit() - Deinit function for ISHTP client
 * @cros_ish_cl: ISHTP client instance
 *
 * Unlink and free cros_ec client
 */
static void cros_ish_deinit(struct ishtp_cl *cros_ish_cl)
{
        ishtp_set_connection_state(cros_ish_cl, ISHTP_CL_DISCONNECTING);
        ishtp_cl_disconnect(cros_ish_cl);
        ishtp_cl_unlink(cros_ish_cl);
        ishtp_cl_flush_queues(cros_ish_cl);

        /* Disband and free all Tx and Rx client-level rings */
        ishtp_cl_free(cros_ish_cl);
}

/**
 * prepare_cros_ec_rx() - Check & prepare receive buffer
 * @ec_dev: CrOS EC MFD device.
 * @in_msg: Incoming message buffer
 * @msg: cros_ec command used to send & receive data
 *
 * Return: 0 for success, negative error code for failure.
 *
 * Check the received buffer. Convert to cros_ec_command format.
 */
static int prepare_cros_ec_rx(struct cros_ec_device *ec_dev,
                              const struct cros_ish_in_msg *in_msg,
                              struct cros_ec_command *msg)
{
        u8 sum = 0;
        int i, rv, offset;

        /* Check response error code */
        msg->result = in_msg->ec_response.result;
        rv = cros_ec_check_result(ec_dev, msg);
        if (rv < 0)
                return rv;

        if (in_msg->ec_response.data_len > msg->insize) {
                dev_err(ec_dev->dev, "Packet too long (%d bytes, expected %d)",
                        in_msg->ec_response.data_len, msg->insize);
                return -ENOSPC;
        }

        /* Copy response packet payload and compute checksum */
        for (i = 0; i < sizeof(struct ec_host_response); i++)
                sum += ((u8 *)in_msg)[IN_MSG_EC_RESPONSE_PREAMBLE + i];

        offset = sizeof(struct cros_ish_in_msg);
        for (i = 0; i < in_msg->ec_response.data_len; i++)
                sum += msg->data[i] = ((u8 *)in_msg)[offset + i];

        if (sum) {
                dev_dbg(ec_dev->dev, "Bad received packet checksum %d\n", sum);
                return -EBADMSG;
        }

        return 0;
}

static int cros_ec_pkt_xfer_ish(struct cros_ec_device *ec_dev,
                                struct cros_ec_command *msg)
{
        int rv;
        struct ishtp_cl *cros_ish_cl = ec_dev->priv;
        struct ishtp_cl_data *client_data = ishtp_get_client_data(cros_ish_cl);
        struct device *dev = cl_data_to_dev(client_data);
        struct cros_ish_in_msg *in_msg = (struct cros_ish_in_msg *)ec_dev->din;
        struct cros_ish_out_msg *out_msg =
                (struct cros_ish_out_msg *)ec_dev->dout;
        size_t in_size = sizeof(struct cros_ish_in_msg) + msg->insize;
        size_t out_size = sizeof(struct cros_ish_out_msg) + msg->outsize;

        /* Sanity checks */
        if (in_size > ec_dev->din_size) {
                dev_err(dev,
                        "Incoming payload size %zu is too large for ec_dev->din_size %d\n",
                        in_size, ec_dev->din_size);
                return -EMSGSIZE;
        }

        if (out_size > ec_dev->dout_size) {
                dev_err(dev,
                        "Outgoing payload size %zu is too large for ec_dev->dout_size %d\n",
                        out_size, ec_dev->dout_size);
                return -EMSGSIZE;
        }

        /* Proceed only if reset-init is not in progress */
        if (!down_read_trylock(&init_lock)) {
                dev_warn(dev,
                         "Host is not ready to send messages to ISH. Try again\n");
                return -EAGAIN;
        }

        /* Prepare the package to be sent over ISH TP */
        out_msg->hdr.channel = CROS_EC_COMMAND;
        out_msg->hdr.status = 0;

        ec_dev->dout += OUT_MSG_EC_REQUEST_PREAMBLE;
        cros_ec_prepare_tx(ec_dev, msg);
        ec_dev->dout -= OUT_MSG_EC_REQUEST_PREAMBLE;

        dev_dbg(dev,
                "out_msg: struct_ver=0x%x checksum=0x%x command=0x%x command_ver=0x%x data_len=0x%x\n",
                out_msg->ec_request.struct_version,
                out_msg->ec_request.checksum,
                out_msg->ec_request.command,
                out_msg->ec_request.command_version,
                out_msg->ec_request.data_len);

        /* Send command to ISH EC firmware and read response */
        rv = ish_send(client_data,
                      (u8 *)out_msg, out_size,
                      (u8 *)in_msg, in_size);
        if (rv < 0)
                goto end_error;

        rv = prepare_cros_ec_rx(ec_dev, in_msg, msg);
        if (rv)
                goto end_error;

        rv = in_msg->ec_response.data_len;

        dev_dbg(dev,
                "in_msg: struct_ver=0x%x checksum=0x%x result=0x%x data_len=0x%x\n",
                in_msg->ec_response.struct_version,
                in_msg->ec_response.checksum,
                in_msg->ec_response.result,
                in_msg->ec_response.data_len);

end_error:
        if (msg->command == EC_CMD_REBOOT_EC)
                msleep(EC_REBOOT_DELAY_MS);

        up_read(&init_lock);

        return rv;
}

static int cros_ec_dev_init(struct ishtp_cl_data *client_data)
{
        struct cros_ec_device *ec_dev;
        struct device *dev = cl_data_to_dev(client_data);

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

        client_data->ec_dev = ec_dev;
        dev->driver_data = ec_dev;

        ec_dev->dev = dev;
        ec_dev->priv = client_data->cros_ish_cl;
        ec_dev->cmd_xfer = NULL;
        ec_dev->pkt_xfer = cros_ec_pkt_xfer_ish;
        ec_dev->phys_name = dev_name(dev);
        ec_dev->din_size = sizeof(struct cros_ish_in_msg) +
                           sizeof(struct ec_response_get_protocol_info);
        ec_dev->dout_size = sizeof(struct cros_ish_out_msg);

        return cros_ec_register(ec_dev);
}

static void reset_handler(struct work_struct *work)
{
        int rv;
        struct device *dev;
        struct ishtp_cl *cros_ish_cl;
        struct ishtp_cl_device *cl_device;
        struct ishtp_cl_data *client_data =
                container_of(work, struct ishtp_cl_data, work_ishtp_reset);

        /* Lock for reset to complete */
        down_write(&init_lock);

        cros_ish_cl = client_data->cros_ish_cl;
        cl_device = client_data->cl_device;

        /* Unlink, flush queues & start again */
        ishtp_cl_unlink(cros_ish_cl);
        ishtp_cl_flush_queues(cros_ish_cl);
        ishtp_cl_free(cros_ish_cl);

        cros_ish_cl = ishtp_cl_allocate(cl_device);
        if (!cros_ish_cl) {
                up_write(&init_lock);
                return;
        }

        ishtp_set_drvdata(cl_device, cros_ish_cl);
        ishtp_set_client_data(cros_ish_cl, client_data);
        client_data->cros_ish_cl = cros_ish_cl;

        rv = cros_ish_init(cros_ish_cl);
        if (rv) {
                ishtp_cl_free(cros_ish_cl);
                dev_err(cl_data_to_dev(client_data), "Reset Failed\n");
                up_write(&init_lock);
                return;
        }

        /* Refresh ec_dev device pointers */
        client_data->ec_dev->priv = client_data->cros_ish_cl;
        dev = cl_data_to_dev(client_data);
        dev->driver_data = client_data->ec_dev;

        dev_info(cl_data_to_dev(client_data), "Chrome EC ISH reset done\n");

        up_write(&init_lock);
}

/**
 * cros_ec_ishtp_probe() - ISHTP client driver probe callback
 * @cl_device: ISHTP client device instance
 *
 * Return: 0 for success, negative error code for failure.
 */
static int cros_ec_ishtp_probe(struct ishtp_cl_device *cl_device)
{
        int rv;
        struct ishtp_cl *cros_ish_cl;
        struct ishtp_cl_data *client_data =
                devm_kzalloc(ishtp_device(cl_device),
                             sizeof(*client_data), GFP_KERNEL);
        if (!client_data)
                return -ENOMEM;

        /* Lock for initialization to complete */
        down_write(&init_lock);

        cros_ish_cl = ishtp_cl_allocate(cl_device);
        if (!cros_ish_cl) {
                rv = -ENOMEM;
                goto end_ishtp_cl_alloc_error;
        }

        ishtp_set_drvdata(cl_device, cros_ish_cl);
        ishtp_set_client_data(cros_ish_cl, client_data);
        client_data->cros_ish_cl = cros_ish_cl;
        client_data->cl_device = cl_device;

        init_waitqueue_head(&client_data->response.wait_queue);

        INIT_WORK(&client_data->work_ishtp_reset,
                  reset_handler);
        INIT_WORK(&client_data->work_ec_evt,
                  ish_evt_handler);

        rv = cros_ish_init(cros_ish_cl);
        if (rv)
                goto end_ishtp_cl_init_error;

        ishtp_get_device(cl_device);

        up_write(&init_lock);

        /* Register croc_ec_dev mfd */
        rv = cros_ec_dev_init(client_data);
        if (rv) {
                down_write(&init_lock);
                goto end_cros_ec_dev_init_error;
        }

        return 0;

end_cros_ec_dev_init_error:
        ishtp_set_connection_state(cros_ish_cl, ISHTP_CL_DISCONNECTING);
        ishtp_cl_disconnect(cros_ish_cl);
        ishtp_cl_unlink(cros_ish_cl);
        ishtp_cl_flush_queues(cros_ish_cl);
        ishtp_put_device(cl_device);
end_ishtp_cl_init_error:
        ishtp_cl_free(cros_ish_cl);
end_ishtp_cl_alloc_error:
        up_write(&init_lock);
        return rv;
}

/**
 * cros_ec_ishtp_remove() - ISHTP client driver remove callback
 * @cl_device: ISHTP client device instance
 *
 * Return: 0
 */
static int cros_ec_ishtp_remove(struct ishtp_cl_device *cl_device)
{
        struct ishtp_cl *cros_ish_cl = ishtp_get_drvdata(cl_device);
        struct ishtp_cl_data *client_data = ishtp_get_client_data(cros_ish_cl);

        cancel_work_sync(&client_data->work_ishtp_reset);
        cancel_work_sync(&client_data->work_ec_evt);
        cros_ish_deinit(cros_ish_cl);
        ishtp_put_device(cl_device);

        return 0;
}

/**
 * cros_ec_ishtp_reset() - ISHTP client driver reset callback
 * @cl_device: ISHTP client device instance
 *
 * Return: 0
 */
static int cros_ec_ishtp_reset(struct ishtp_cl_device *cl_device)
{
        struct ishtp_cl *cros_ish_cl = ishtp_get_drvdata(cl_device);
        struct ishtp_cl_data *client_data = ishtp_get_client_data(cros_ish_cl);

        schedule_work(&client_data->work_ishtp_reset);

        return 0;
}

/**
 * cros_ec_ishtp_suspend() - ISHTP client driver suspend callback
 * @device: device instance
 *
 * Return: 0 for success, negative error code for failure.
 */
static int __maybe_unused cros_ec_ishtp_suspend(struct device *device)
{
        struct ishtp_cl_device *cl_device = ishtp_dev_to_cl_device(device);
        struct ishtp_cl *cros_ish_cl = ishtp_get_drvdata(cl_device);
        struct ishtp_cl_data *client_data = ishtp_get_client_data(cros_ish_cl);

        return cros_ec_suspend(client_data->ec_dev);
}

/**
 * cros_ec_ishtp_resume() - ISHTP client driver resume callback
 * @device: device instance
 *
 * Return: 0 for success, negative error code for failure.
 */
static int __maybe_unused cros_ec_ishtp_resume(struct device *device)
{
        struct ishtp_cl_device *cl_device = ishtp_dev_to_cl_device(device);
        struct ishtp_cl *cros_ish_cl = ishtp_get_drvdata(cl_device);
        struct ishtp_cl_data *client_data = ishtp_get_client_data(cros_ish_cl);

        return cros_ec_resume(client_data->ec_dev);
}

static SIMPLE_DEV_PM_OPS(cros_ec_ishtp_pm_ops, cros_ec_ishtp_suspend,
                         cros_ec_ishtp_resume);

static struct ishtp_cl_driver   cros_ec_ishtp_driver = {
        .name = "cros_ec_ishtp",
        .guid = &cros_ish_guid,
        .probe = cros_ec_ishtp_probe,
        .remove = cros_ec_ishtp_remove,
        .reset = cros_ec_ishtp_reset,
        .driver = {
                .pm = &cros_ec_ishtp_pm_ops,
        },
};

static int __init cros_ec_ishtp_mod_init(void)
{
        return ishtp_cl_driver_register(&cros_ec_ishtp_driver, THIS_MODULE);
}

static void __exit cros_ec_ishtp_mod_exit(void)
{
        ishtp_cl_driver_unregister(&cros_ec_ishtp_driver);
}

module_init(cros_ec_ishtp_mod_init);
module_exit(cros_ec_ishtp_mod_exit);

MODULE_DESCRIPTION("ChromeOS EC ISHTP Client Driver");
MODULE_AUTHOR("Rushikesh S Kadam <rushikesh.s.kadam@intel.com>");

MODULE_LICENSE("GPL v2");
MODULE_ALIAS("ishtp:*");