diff options
Diffstat (limited to 'drivers/platform/chrome/wilco_ec/mailbox.c')
| -rw-r--r-- | drivers/platform/chrome/wilco_ec/mailbox.c | 215 |
1 files changed, 215 insertions, 0 deletions
diff --git a/drivers/platform/chrome/wilco_ec/mailbox.c b/drivers/platform/chrome/wilco_ec/mailbox.c new file mode 100644 index 000000000..0f98358ea --- /dev/null +++ b/drivers/platform/chrome/wilco_ec/mailbox.c @@ -0,0 +1,215 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Mailbox interface for Wilco Embedded Controller + * + * Copyright 2018 Google LLC + * + * The Wilco EC is similar to a typical ChromeOS embedded controller. + * It uses the same MEC based low-level communication and a similar + * protocol, but with some important differences. The EC firmware does + * not support the same mailbox commands so it is not registered as a + * cros_ec device type. + * + * Most messages follow a standard format, but there are some exceptions + * and an interface is provided to do direct/raw transactions that do not + * make assumptions about byte placement. + */ + +#include <linux/delay.h> +#include <linux/device.h> +#include <linux/io.h> +#include <linux/platform_data/wilco-ec.h> +#include <linux/platform_device.h> + +#include "../cros_ec_lpc_mec.h" + +/* Version of mailbox interface */ +#define EC_MAILBOX_VERSION 0 + +/* Command to start mailbox transaction */ +#define EC_MAILBOX_START_COMMAND 0xda + +/* Version of EC protocol */ +#define EC_MAILBOX_PROTO_VERSION 3 + +/* Number of header bytes to be counted as data bytes */ +#define EC_MAILBOX_DATA_EXTRA 2 + +/* Maximum timeout */ +#define EC_MAILBOX_TIMEOUT HZ + +/* EC response flags */ +#define EC_CMDR_DATA BIT(0) /* Data ready for host to read */ +#define EC_CMDR_PENDING BIT(1) /* Write pending to EC */ +#define EC_CMDR_BUSY BIT(2) /* EC is busy processing a command */ +#define EC_CMDR_CMD BIT(3) /* Last host write was a command */ + +/** + * wilco_ec_response_timed_out() - Wait for EC response. + * @ec: EC device. + * + * Return: true if EC timed out, false if EC did not time out. + */ +static bool wilco_ec_response_timed_out(struct wilco_ec_device *ec) +{ + unsigned long timeout = jiffies + EC_MAILBOX_TIMEOUT; + + do { + if (!(inb(ec->io_command->start) & + (EC_CMDR_PENDING | EC_CMDR_BUSY))) + return false; + usleep_range(100, 200); + } while (time_before(jiffies, timeout)); + + return true; +} + +/** + * wilco_ec_checksum() - Compute 8-bit checksum over data range. + * @data: Data to checksum. + * @size: Number of bytes to checksum. + * + * Return: 8-bit checksum of provided data. + */ +static u8 wilco_ec_checksum(const void *data, size_t size) +{ + u8 *data_bytes = (u8 *)data; + u8 checksum = 0; + size_t i; + + for (i = 0; i < size; i++) + checksum += data_bytes[i]; + + return checksum; +} + +/** + * wilco_ec_prepare() - Prepare the request structure for the EC. + * @msg: EC message with request information. + * @rq: EC request structure to fill. + */ +static void wilco_ec_prepare(struct wilco_ec_message *msg, + struct wilco_ec_request *rq) +{ + memset(rq, 0, sizeof(*rq)); + rq->struct_version = EC_MAILBOX_PROTO_VERSION; + rq->mailbox_id = msg->type; + rq->mailbox_version = EC_MAILBOX_VERSION; + rq->data_size = msg->request_size; + + /* Checksum header and data */ + rq->checksum = wilco_ec_checksum(rq, sizeof(*rq)); + rq->checksum += wilco_ec_checksum(msg->request_data, msg->request_size); + rq->checksum = -rq->checksum; +} + +/** + * wilco_ec_transfer() - Perform actual data transfer. + * @ec: EC device. + * @msg: EC message data for request and response. + * @rq: Filled in request structure + * + * Context: ec->mailbox_lock should be held while using this function. + * Return: number of bytes received or negative error code on failure. + */ +static int wilco_ec_transfer(struct wilco_ec_device *ec, + struct wilco_ec_message *msg, + struct wilco_ec_request *rq) +{ + struct wilco_ec_response *rs; + u8 checksum; + u8 flag; + + /* Write request header, then data */ + cros_ec_lpc_io_bytes_mec(MEC_IO_WRITE, 0, sizeof(*rq), (u8 *)rq); + cros_ec_lpc_io_bytes_mec(MEC_IO_WRITE, sizeof(*rq), msg->request_size, + msg->request_data); + + /* Start the command */ + outb(EC_MAILBOX_START_COMMAND, ec->io_command->start); + + /* For some commands (eg shutdown) the EC will not respond, that's OK */ + if (msg->flags & WILCO_EC_FLAG_NO_RESPONSE) { + dev_dbg(ec->dev, "EC does not respond to this command\n"); + return 0; + } + + /* Wait for it to complete */ + if (wilco_ec_response_timed_out(ec)) { + dev_dbg(ec->dev, "response timed out\n"); + return -ETIMEDOUT; + } + + /* Check result */ + flag = inb(ec->io_data->start); + if (flag) { + dev_dbg(ec->dev, "bad response: 0x%02x\n", flag); + return -EIO; + } + + /* Read back response */ + rs = ec->data_buffer; + checksum = cros_ec_lpc_io_bytes_mec(MEC_IO_READ, 0, + sizeof(*rs) + EC_MAILBOX_DATA_SIZE, + (u8 *)rs); + if (checksum) { + dev_dbg(ec->dev, "bad packet checksum 0x%02x\n", rs->checksum); + return -EBADMSG; + } + + if (rs->result) { + dev_dbg(ec->dev, "EC reported failure: 0x%02x\n", rs->result); + return -EBADMSG; + } + + if (rs->data_size != EC_MAILBOX_DATA_SIZE) { + dev_dbg(ec->dev, "unexpected packet size (%u != %u)\n", + rs->data_size, EC_MAILBOX_DATA_SIZE); + return -EMSGSIZE; + } + + if (rs->data_size < msg->response_size) { + dev_dbg(ec->dev, "EC didn't return enough data (%u < %zu)\n", + rs->data_size, msg->response_size); + return -EMSGSIZE; + } + + memcpy(msg->response_data, rs->data, msg->response_size); + + return rs->data_size; +} + +/** + * wilco_ec_mailbox() - Send EC request and receive EC response. + * @ec: EC device. + * @msg: EC message data for request and response. + * + * On entry msg->type, msg->request_size, and msg->request_data should all be + * filled in. If desired, msg->flags can be set. + * + * If a response is expected, msg->response_size should be set, and + * msg->response_data should point to a buffer with enough space. On exit + * msg->response_data will be filled. + * + * Return: number of bytes received or negative error code on failure. + */ +int wilco_ec_mailbox(struct wilco_ec_device *ec, struct wilco_ec_message *msg) +{ + struct wilco_ec_request *rq; + int ret; + + dev_dbg(ec->dev, "type=%04x flags=%02x rslen=%zu rqlen=%zu\n", + msg->type, msg->flags, msg->response_size, msg->request_size); + + mutex_lock(&ec->mailbox_lock); + /* Prepare request packet */ + rq = ec->data_buffer; + wilco_ec_prepare(msg, rq); + + ret = wilco_ec_transfer(ec, msg, rq); + mutex_unlock(&ec->mailbox_lock); + + return ret; + +} +EXPORT_SYMBOL_GPL(wilco_ec_mailbox); |