/*
 * ChromeOS EC communication protocol helper functions
 *
 * Copyright (C) 2015 Google, Inc
 *
 * This software is licensed under the terms of the GNU General Public
 * License version 2, as published by the Free Software Foundation, and
 * may be copied, distributed, and modified under those terms.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 */

#include <linux/mfd/cros_ec.h>
#include <linux/delay.h>
#include <linux/device.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <asm/unaligned.h>

#define EC_COMMAND_RETRIES      50

static int prepare_packet(struct cros_ec_device *ec_dev,
                          struct cros_ec_command *msg)
{
        struct ec_host_request *request;
        u8 *out;
        int i;
        u8 csum = 0;

        BUG_ON(ec_dev->proto_version != EC_HOST_REQUEST_VERSION);
        BUG_ON(msg->outsize + sizeof(*request) > ec_dev->dout_size);

        out = ec_dev->dout;
        request = (struct ec_host_request *)out;
        request->struct_version = EC_HOST_REQUEST_VERSION;
        request->checksum = 0;
        request->command = msg->command;
        request->command_version = msg->version;
        request->reserved = 0;
        request->data_len = msg->outsize;

        for (i = 0; i < sizeof(*request); i++)
                csum += out[i];

        /* Copy data and update checksum */
        memcpy(out + sizeof(*request), msg->data, msg->outsize);
        for (i = 0; i < msg->outsize; i++)
                csum += msg->data[i];

        request->checksum = -csum;

        return sizeof(*request) + msg->outsize;
}

static int send_command(struct cros_ec_device *ec_dev,
                        struct cros_ec_command *msg)
{
        int ret;
        int (*xfer_fxn)(struct cros_ec_device *ec, struct cros_ec_command *msg);

        if (ec_dev->proto_version > 2)
                xfer_fxn = ec_dev->pkt_xfer;
        else
                xfer_fxn = ec_dev->cmd_xfer;

        ret = (*xfer_fxn)(ec_dev, msg);
        if (msg->result == EC_RES_IN_PROGRESS) {
                int i;
                struct cros_ec_command *status_msg;
                struct ec_response_get_comms_status *status;

                status_msg = kmalloc(sizeof(*status_msg) + sizeof(*status),
                                     GFP_KERNEL);
                if (!status_msg)
                        return -ENOMEM;

                status_msg->version = 0;
                status_msg->command = EC_CMD_GET_COMMS_STATUS;
                status_msg->insize = sizeof(*status);
                status_msg->outsize = 0;

                /*
                 * Query the EC's status until it's no longer busy or
                 * we encounter an error.
                 */
                for (i = 0; i < EC_COMMAND_RETRIES; i++) {
                        usleep_range(10000, 11000);

                        ret = (*xfer_fxn)(ec_dev, status_msg);
                        if (ret == -EAGAIN)
                                continue;
                        if (ret < 0)
                                break;

                        msg->result = status_msg->result;
                        if (status_msg->result != EC_RES_SUCCESS)
                                break;

                        status = (struct ec_response_get_comms_status *)
                                 status_msg->data;
                        if (!(status->flags & EC_COMMS_STATUS_PROCESSING))
                                break;
                }

                kfree(status_msg);
        }

        return ret;
}

int cros_ec_prepare_tx(struct cros_ec_device *ec_dev,
                       struct cros_ec_command *msg)
{
        u8 *out;
        u8 csum;
        int i;

        if (ec_dev->proto_version > 2)
                return prepare_packet(ec_dev, msg);

        BUG_ON(msg->outsize > EC_PROTO2_MAX_PARAM_SIZE);
        out = ec_dev->dout;
        out[0] = EC_CMD_VERSION0 + msg->version;
        out[1] = msg->command;
        out[2] = msg->outsize;
        csum = out[0] + out[1] + out[2];
        for (i = 0; i < msg->outsize; i++)
                csum += out[EC_MSG_TX_HEADER_BYTES + i] = msg->data[i];
        out[EC_MSG_TX_HEADER_BYTES + msg->outsize] = csum;

        return EC_MSG_TX_PROTO_BYTES + msg->outsize;
}
EXPORT_SYMBOL(cros_ec_prepare_tx);

int cros_ec_check_result(struct cros_ec_device *ec_dev,
                         struct cros_ec_command *msg)
{
        switch (msg->result) {
        case EC_RES_SUCCESS:
                return 0;
        case EC_RES_IN_PROGRESS:
                dev_dbg(ec_dev->dev, "command 0x%02x in progress\n",
                        msg->command);
                return -EAGAIN;
        default:
                dev_dbg(ec_dev->dev, "command 0x%02x returned %d\n",
                        msg->command, msg->result);
                return 0;
        }
}
EXPORT_SYMBOL(cros_ec_check_result);

/*
 * cros_ec_get_host_event_wake_mask
 *
 * Get the mask of host events that cause wake from suspend.
 *
 * @ec_dev: EC device to call
 * @msg: message structure to use
 * @mask: result when function returns >=0.
 *
 * LOCKING:
 * the caller has ec_dev->lock mutex, or the caller knows there is
 * no other command in progress.
 */
static int cros_ec_get_host_event_wake_mask(struct cros_ec_device *ec_dev,
                                            struct cros_ec_command *msg,
                                            uint32_t *mask)
{
        struct ec_response_host_event_mask *r;
        int ret;

        msg->command = EC_CMD_HOST_EVENT_GET_WAKE_MASK;
        msg->version = 0;
        msg->outsize = 0;
        msg->insize = sizeof(*r);

        ret = send_command(ec_dev, msg);
        if (ret > 0) {
                r = (struct ec_response_host_event_mask *)msg->data;
                *mask = r->mask;
        }

        return ret;
}

static int cros_ec_host_command_proto_query(struct cros_ec_device *ec_dev,
                                            int devidx,
                                            struct cros_ec_command *msg)
{
        /*
         * Try using v3+ to query for supported protocols. If this
         * command fails, fall back to v2. Returns the highest protocol
         * supported by the EC.
         * Also sets the max request/response/passthru size.
         */
        int ret;

        if (!ec_dev->pkt_xfer)
                return -EPROTONOSUPPORT;

        memset(msg, 0, sizeof(*msg));
        msg->command = EC_CMD_PASSTHRU_OFFSET(devidx) | EC_CMD_GET_PROTOCOL_INFO;
        msg->insize = sizeof(struct ec_response_get_protocol_info);

        ret = send_command(ec_dev, msg);

        if (ret < 0) {
                dev_dbg(ec_dev->dev,
                        "failed to check for EC[%d] protocol version: %d\n",
                        devidx, ret);
                return ret;
        }

        if (devidx > 0 && msg->result == EC_RES_INVALID_COMMAND)
                return -ENODEV;
        else if (msg->result != EC_RES_SUCCESS)
                return msg->result;

        return 0;
}

static int cros_ec_host_command_proto_query_v2(struct cros_ec_device *ec_dev)
{
        struct cros_ec_command *msg;
        struct ec_params_hello *hello_params;
        struct ec_response_hello *hello_response;
        int ret;
        int len = max(sizeof(*hello_params), sizeof(*hello_response));

        msg = kmalloc(sizeof(*msg) + len, GFP_KERNEL);
        if (!msg)
                return -ENOMEM;

        msg->version = 0;
        msg->command = EC_CMD_HELLO;
        hello_params = (struct ec_params_hello *)msg->data;
        msg->outsize = sizeof(*hello_params);
        hello_response = (struct ec_response_hello *)msg->data;
        msg->insize = sizeof(*hello_response);

        hello_params->in_data = 0xa0b0c0d0;

        ret = send_command(ec_dev, msg);

        if (ret < 0) {
                dev_dbg(ec_dev->dev,
                        "EC failed to respond to v2 hello: %d\n",
                        ret);
                goto exit;
        } else if (msg->result != EC_RES_SUCCESS) {
                dev_err(ec_dev->dev,
                        "EC responded to v2 hello with error: %d\n",
                        msg->result);
                ret = msg->result;
                goto exit;
        } else if (hello_response->out_data != 0xa1b2c3d4) {
                dev_err(ec_dev->dev,
                        "EC responded to v2 hello with bad result: %u\n",
                        hello_response->out_data);
                ret = -EBADMSG;
                goto exit;
        }

        ret = 0;

 exit:
        kfree(msg);
        return ret;
}

/*
 * cros_ec_get_host_command_version_mask
 *
 * Get the version mask of a given command.
 *
 * @ec_dev: EC device to call
 * @msg: message structure to use
 * @cmd: command to get the version of.
 * @mask: result when function returns 0.
 *
 * @return 0 on success, error code otherwise
 *
 * LOCKING:
 * the caller has ec_dev->lock mutex or the caller knows there is
 * no other command in progress.
 */
static int cros_ec_get_host_command_version_mask(struct cros_ec_device *ec_dev,
        u16 cmd, u32 *mask)
{
        struct ec_params_get_cmd_versions *pver;
        struct ec_response_get_cmd_versions *rver;
        struct cros_ec_command *msg;
        int ret;

        msg = kmalloc(sizeof(*msg) + max(sizeof(*rver), sizeof(*pver)),
                      GFP_KERNEL);
        if (!msg)
                return -ENOMEM;

        msg->version = 0;
        msg->command = EC_CMD_GET_CMD_VERSIONS;
        msg->insize = sizeof(*rver);
        msg->outsize = sizeof(*pver);

        pver = (struct ec_params_get_cmd_versions *)msg->data;
        pver->cmd = cmd;

        ret = send_command(ec_dev, msg);
        if (ret > 0) {
                rver = (struct ec_response_get_cmd_versions *)msg->data;
                *mask = rver->version_mask;
        }

        kfree(msg);

        return ret;
}

int cros_ec_query_all(struct cros_ec_device *ec_dev)
{
        struct device *dev = ec_dev->dev;
        struct cros_ec_command *proto_msg;
        struct ec_response_get_protocol_info *proto_info;
        u32 ver_mask = 0;
        int ret;

        proto_msg = kzalloc(sizeof(*proto_msg) + sizeof(*proto_info),
                            GFP_KERNEL);
        if (!proto_msg)
                return -ENOMEM;

        /* First try sending with proto v3. */
        ec_dev->proto_version = 3;
        ret = cros_ec_host_command_proto_query(ec_dev, 0, proto_msg);

        if (ret == 0) {
                proto_info = (struct ec_response_get_protocol_info *)
                        proto_msg->data;
                ec_dev->max_request = proto_info->max_request_packet_size -
                        sizeof(struct ec_host_request);
                ec_dev->max_response = proto_info->max_response_packet_size -
                        sizeof(struct ec_host_response);
                ec_dev->proto_version =
                        min(EC_HOST_REQUEST_VERSION,
                                        fls(proto_info->protocol_versions) - 1);
                dev_dbg(ec_dev->dev,
                        "using proto v%u\n",
                        ec_dev->proto_version);

                ec_dev->din_size = ec_dev->max_response +
                        sizeof(struct ec_host_response) +
                        EC_MAX_RESPONSE_OVERHEAD;
                ec_dev->dout_size = ec_dev->max_request +
                        sizeof(struct ec_host_request) +
                        EC_MAX_REQUEST_OVERHEAD;

                /*
                 * Check for PD
                 */
                ret = cros_ec_host_command_proto_query(ec_dev, 1, proto_msg);

                if (ret) {
                        dev_dbg(ec_dev->dev, "no PD chip found: %d\n", ret);
                        ec_dev->max_passthru = 0;
                } else {
                        dev_dbg(ec_dev->dev, "found PD chip\n");
                        ec_dev->max_passthru =
                                proto_info->max_request_packet_size -
                                sizeof(struct ec_host_request);
                }
        } else {
                /* Try querying with a v2 hello message. */
                ec_dev->proto_version = 2;
                ret = cros_ec_host_command_proto_query_v2(ec_dev);

                if (ret == 0) {
                        /* V2 hello succeeded. */
                        dev_dbg(ec_dev->dev, "falling back to proto v2\n");

                        ec_dev->max_request = EC_PROTO2_MAX_PARAM_SIZE;
                        ec_dev->max_response = EC_PROTO2_MAX_PARAM_SIZE;
                        ec_dev->max_passthru = 0;
                        ec_dev->pkt_xfer = NULL;
                        ec_dev->din_size = EC_PROTO2_MSG_BYTES;
                        ec_dev->dout_size = EC_PROTO2_MSG_BYTES;
                } else {
                        /*
                         * It's possible for a test to occur too early when
                         * the EC isn't listening. If this happens, we'll
                         * test later when the first command is run.
                         */
                        ec_dev->proto_version = EC_PROTO_VERSION_UNKNOWN;
                        dev_dbg(ec_dev->dev, "EC query failed: %d\n", ret);
                        goto exit;
                }
        }

        devm_kfree(dev, ec_dev->din);
        devm_kfree(dev, ec_dev->dout);

        ec_dev->din = devm_kzalloc(dev, ec_dev->din_size, GFP_KERNEL);
        if (!ec_dev->din) {
                ret = -ENOMEM;
                goto exit;
        }

        ec_dev->dout = devm_kzalloc(dev, ec_dev->dout_size, GFP_KERNEL);
        if (!ec_dev->dout) {
                devm_kfree(dev, ec_dev->din);
                ret = -ENOMEM;
                goto exit;
        }

        /* Probe if MKBP event is supported */
        ret = cros_ec_get_host_command_version_mask(ec_dev,
                                                    EC_CMD_GET_NEXT_EVENT,
                                                    &ver_mask);
        if (ret < 0 || ver_mask == 0)
                ec_dev->mkbp_event_supported = 0;
        else
                ec_dev->mkbp_event_supported = 1;

        /*
         * Get host event wake mask, assume all events are wake events
         * if unavailable.
         */
        ret = cros_ec_get_host_event_wake_mask(ec_dev, proto_msg,
                                               &ec_dev->host_event_wake_mask);
        if (ret < 0)
                ec_dev->host_event_wake_mask = U32_MAX;

        ret = 0;

exit:
        kfree(proto_msg);
        return ret;
}
EXPORT_SYMBOL(cros_ec_query_all);

int cros_ec_cmd_xfer(struct cros_ec_device *ec_dev,
                     struct cros_ec_command *msg)
{
        int ret;

        mutex_lock(&ec_dev->lock);
        if (ec_dev->proto_version == EC_PROTO_VERSION_UNKNOWN) {
                ret = cros_ec_query_all(ec_dev);
                if (ret) {
                        dev_err(ec_dev->dev,
                                "EC version unknown and query failed; aborting command\n");
                        mutex_unlock(&ec_dev->lock);
                        return ret;
                }
        }

        if (msg->insize > ec_dev->max_response) {
                dev_dbg(ec_dev->dev, "clamping message receive buffer\n");
                msg->insize = ec_dev->max_response;
        }

        if (msg->command < EC_CMD_PASSTHRU_OFFSET(1)) {
                if (msg->outsize > ec_dev->max_request) {
                        dev_err(ec_dev->dev,
                                "request of size %u is too big (max: %u)\n",
                                msg->outsize,
                                ec_dev->max_request);
                        mutex_unlock(&ec_dev->lock);
                        return -EMSGSIZE;
                }
        } else {
                if (msg->outsize > ec_dev->max_passthru) {
                        dev_err(ec_dev->dev,
                                "passthru rq of size %u is too big (max: %u)\n",
                                msg->outsize,
                                ec_dev->max_passthru);
                        mutex_unlock(&ec_dev->lock);
                        return -EMSGSIZE;
                }
        }
        ret = send_command(ec_dev, msg);
        mutex_unlock(&ec_dev->lock);

        return ret;
}
EXPORT_SYMBOL(cros_ec_cmd_xfer);

int cros_ec_cmd_xfer_status(struct cros_ec_device *ec_dev,
                            struct cros_ec_command *msg)
{
        int ret;

        ret = cros_ec_cmd_xfer(ec_dev, msg);
        if (ret < 0) {
                dev_err(ec_dev->dev, "Command xfer error (err:%d)\n", ret);
        } else if (msg->result != EC_RES_SUCCESS) {
                dev_dbg(ec_dev->dev, "Command result (err: %d)\n", msg->result);
                return -EPROTO;
        }

        return ret;
}
EXPORT_SYMBOL(cros_ec_cmd_xfer_status);

static int get_next_event(struct cros_ec_device *ec_dev)
{
        u8 buffer[sizeof(struct cros_ec_command) + sizeof(ec_dev->event_data)];
        struct cros_ec_command *msg = (struct cros_ec_command *)&buffer;
        int ret;

        if (ec_dev->suspended) {
                dev_dbg(ec_dev->dev, "Device suspended.\n");
                return -EHOSTDOWN;
        }

        msg->version = 0;
        msg->command = EC_CMD_GET_NEXT_EVENT;
        msg->insize = sizeof(ec_dev->event_data);
        msg->outsize = 0;

        ret = cros_ec_cmd_xfer(ec_dev, msg);
        if (ret > 0) {
                ec_dev->event_size = ret - 1;
                memcpy(&ec_dev->event_data, msg->data,
                       sizeof(ec_dev->event_data));
        }

        return ret;
}

static int get_keyboard_state_event(struct cros_ec_device *ec_dev)
{
        u8 buffer[sizeof(struct cros_ec_command) +
                  sizeof(ec_dev->event_data.data)];
        struct cros_ec_command *msg = (struct cros_ec_command *)&buffer;

        msg->version = 0;
        msg->command = EC_CMD_MKBP_STATE;
        msg->insize = sizeof(ec_dev->event_data.data);
        msg->outsize = 0;

        ec_dev->event_size = cros_ec_cmd_xfer(ec_dev, msg);
        ec_dev->event_data.event_type = EC_MKBP_EVENT_KEY_MATRIX;
        memcpy(&ec_dev->event_data.data, msg->data,
               sizeof(ec_dev->event_data.data));

        return ec_dev->event_size;
}

int cros_ec_get_next_event(struct cros_ec_device *ec_dev, bool *wake_event)
{
        u32 host_event;
        int ret;

        if (!ec_dev->mkbp_event_supported) {
                ret = get_keyboard_state_event(ec_dev);
                if (ret < 0)
                        return ret;

                if (wake_event)
                        *wake_event = true;

                return ret;
        }

        ret = get_next_event(ec_dev);
        if (ret < 0)
                return ret;

        if (wake_event) {
                host_event = cros_ec_get_host_event(ec_dev);

                /* Consider non-host_event as wake event */
                *wake_event = !host_event ||
                              !!(host_event & ec_dev->host_event_wake_mask);
        }

        return ret;
}
EXPORT_SYMBOL(cros_ec_get_next_event);

u32 cros_ec_get_host_event(struct cros_ec_device *ec_dev)
{
        u32 host_event;

        BUG_ON(!ec_dev->mkbp_event_supported);

        if (ec_dev->event_data.event_type != EC_MKBP_EVENT_HOST_EVENT)
                return 0;

        if (ec_dev->event_size != sizeof(host_event)) {
                dev_warn(ec_dev->dev, "Invalid host event size\n");
                return 0;
        }

        host_event = get_unaligned_le32(&ec_dev->event_data.data.host_event);

        return host_event;
}
EXPORT_SYMBOL(cros_ec_get_host_event);