1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Mailbox interface for Wilco Embedded Controller 4 * 5 * Copyright 2018 Google LLC 6 * 7 * The Wilco EC is similar to a typical ChromeOS embedded controller. 8 * It uses the same MEC based low-level communication and a similar 9 * protocol, but with some important differences. The EC firmware does 10 * not support the same mailbox commands so it is not registered as a 11 * cros_ec device type. 12 * 13 * Most messages follow a standard format, but there are some exceptions 14 * and an interface is provided to do direct/raw transactions that do not 15 * make assumptions about byte placement. 16 */ 17 18 #include <linux/delay.h> 19 #include <linux/device.h> 20 #include <linux/io.h> 21 #include <linux/platform_data/wilco-ec.h> 22 #include <linux/platform_device.h> 23 24 #include "../cros_ec_lpc_mec.h" 25 26 /* Version of mailbox interface */ 27 #define EC_MAILBOX_VERSION 0 28 29 /* Command to start mailbox transaction */ 30 #define EC_MAILBOX_START_COMMAND 0xda 31 32 /* Version of EC protocol */ 33 #define EC_MAILBOX_PROTO_VERSION 3 34 35 /* Number of header bytes to be counted as data bytes */ 36 #define EC_MAILBOX_DATA_EXTRA 2 37 38 /* Maximum timeout */ 39 #define EC_MAILBOX_TIMEOUT HZ 40 41 /* EC response flags */ 42 #define EC_CMDR_DATA BIT(0) /* Data ready for host to read */ 43 #define EC_CMDR_PENDING BIT(1) /* Write pending to EC */ 44 #define EC_CMDR_BUSY BIT(2) /* EC is busy processing a command */ 45 #define EC_CMDR_CMD BIT(3) /* Last host write was a command */ 46 47 /** 48 * wilco_ec_response_timed_out() - Wait for EC response. 49 * @ec: EC device. 50 * 51 * Return: true if EC timed out, false if EC did not time out. 52 */ 53 static bool wilco_ec_response_timed_out(struct wilco_ec_device *ec) 54 { 55 unsigned long timeout = jiffies + EC_MAILBOX_TIMEOUT; 56 57 do { 58 if (!(inb(ec->io_command->start) & 59 (EC_CMDR_PENDING | EC_CMDR_BUSY))) 60 return false; 61 usleep_range(100, 200); 62 } while (time_before(jiffies, timeout)); 63 64 return true; 65 } 66 67 /** 68 * wilco_ec_checksum() - Compute 8-bit checksum over data range. 69 * @data: Data to checksum. 70 * @size: Number of bytes to checksum. 71 * 72 * Return: 8-bit checksum of provided data. 73 */ 74 static u8 wilco_ec_checksum(const void *data, size_t size) 75 { 76 u8 *data_bytes = (u8 *)data; 77 u8 checksum = 0; 78 size_t i; 79 80 for (i = 0; i < size; i++) 81 checksum += data_bytes[i]; 82 83 return checksum; 84 } 85 86 /** 87 * wilco_ec_prepare() - Prepare the request structure for the EC. 88 * @msg: EC message with request information. 89 * @rq: EC request structure to fill. 90 */ 91 static void wilco_ec_prepare(struct wilco_ec_message *msg, 92 struct wilco_ec_request *rq) 93 { 94 memset(rq, 0, sizeof(*rq)); 95 rq->struct_version = EC_MAILBOX_PROTO_VERSION; 96 rq->mailbox_id = msg->type; 97 rq->mailbox_version = EC_MAILBOX_VERSION; 98 rq->data_size = msg->request_size; 99 100 /* Checksum header and data */ 101 rq->checksum = wilco_ec_checksum(rq, sizeof(*rq)); 102 rq->checksum += wilco_ec_checksum(msg->request_data, msg->request_size); 103 rq->checksum = -rq->checksum; 104 } 105 106 /** 107 * wilco_ec_transfer() - Perform actual data transfer. 108 * @ec: EC device. 109 * @msg: EC message data for request and response. 110 * @rq: Filled in request structure 111 * 112 * Context: ec->mailbox_lock should be held while using this function. 113 * Return: number of bytes received or negative error code on failure. 114 */ 115 static int wilco_ec_transfer(struct wilco_ec_device *ec, 116 struct wilco_ec_message *msg, 117 struct wilco_ec_request *rq) 118 { 119 struct wilco_ec_response *rs; 120 int ret; 121 u8 flag; 122 123 /* Write request header, then data */ 124 ret = cros_ec_lpc_io_bytes_mec(MEC_IO_WRITE, 0, sizeof(*rq), (u8 *)rq); 125 if (ret < 0) 126 return ret; 127 ret = cros_ec_lpc_io_bytes_mec(MEC_IO_WRITE, sizeof(*rq), msg->request_size, 128 msg->request_data); 129 if (ret < 0) 130 return ret; 131 132 /* Start the command */ 133 outb(EC_MAILBOX_START_COMMAND, ec->io_command->start); 134 135 /* For some commands (eg shutdown) the EC will not respond, that's OK */ 136 if (msg->flags & WILCO_EC_FLAG_NO_RESPONSE) { 137 dev_dbg(ec->dev, "EC does not respond to this command\n"); 138 return 0; 139 } 140 141 /* Wait for it to complete */ 142 if (wilco_ec_response_timed_out(ec)) { 143 dev_dbg(ec->dev, "response timed out\n"); 144 return -ETIMEDOUT; 145 } 146 147 /* Check result */ 148 flag = inb(ec->io_data->start); 149 if (flag) { 150 dev_dbg(ec->dev, "bad response: 0x%02x\n", flag); 151 return -EIO; 152 } 153 154 /* Read back response */ 155 rs = ec->data_buffer; 156 ret = cros_ec_lpc_io_bytes_mec(MEC_IO_READ, 0, 157 sizeof(*rs) + EC_MAILBOX_DATA_SIZE, 158 (u8 *)rs); 159 if (ret < 0) 160 return ret; 161 if (ret) { 162 dev_dbg(ec->dev, "bad packet checksum 0x%02x\n", rs->checksum); 163 return -EBADMSG; 164 } 165 166 if (rs->result) { 167 dev_dbg(ec->dev, "EC reported failure: 0x%02x\n", rs->result); 168 return -EBADMSG; 169 } 170 171 if (rs->data_size != EC_MAILBOX_DATA_SIZE) { 172 dev_dbg(ec->dev, "unexpected packet size (%u != %u)\n", 173 rs->data_size, EC_MAILBOX_DATA_SIZE); 174 return -EMSGSIZE; 175 } 176 177 if (rs->data_size < msg->response_size) { 178 dev_dbg(ec->dev, "EC didn't return enough data (%u < %zu)\n", 179 rs->data_size, msg->response_size); 180 return -EMSGSIZE; 181 } 182 183 memcpy(msg->response_data, rs->data, msg->response_size); 184 185 return rs->data_size; 186 } 187 188 /** 189 * wilco_ec_mailbox() - Send EC request and receive EC response. 190 * @ec: EC device. 191 * @msg: EC message data for request and response. 192 * 193 * On entry msg->type, msg->request_size, and msg->request_data should all be 194 * filled in. If desired, msg->flags can be set. 195 * 196 * If a response is expected, msg->response_size should be set, and 197 * msg->response_data should point to a buffer with enough space. On exit 198 * msg->response_data will be filled. 199 * 200 * Return: number of bytes received or negative error code on failure. 201 */ 202 int wilco_ec_mailbox(struct wilco_ec_device *ec, struct wilco_ec_message *msg) 203 { 204 struct wilco_ec_request *rq; 205 int ret; 206 207 dev_dbg(ec->dev, "type=%04x flags=%02x rslen=%zu rqlen=%zu\n", 208 msg->type, msg->flags, msg->response_size, msg->request_size); 209 210 mutex_lock(&ec->mailbox_lock); 211 /* Prepare request packet */ 212 rq = ec->data_buffer; 213 wilco_ec_prepare(msg, rq); 214 215 ret = wilco_ec_transfer(ec, msg, rq); 216 mutex_unlock(&ec->mailbox_lock); 217 218 return ret; 219 220 } 221 EXPORT_SYMBOL_GPL(wilco_ec_mailbox); 222