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 u8 checksum; 121 u8 flag; 122 size_t size; 123 124 /* Write request header, then data */ 125 cros_ec_lpc_io_bytes_mec(MEC_IO_WRITE, 0, sizeof(*rq), (u8 *)rq); 126 cros_ec_lpc_io_bytes_mec(MEC_IO_WRITE, sizeof(*rq), msg->request_size, 127 msg->request_data); 128 129 /* Start the command */ 130 outb(EC_MAILBOX_START_COMMAND, ec->io_command->start); 131 132 /* For some commands (eg shutdown) the EC will not respond, that's OK */ 133 if (msg->flags & WILCO_EC_FLAG_NO_RESPONSE) { 134 dev_dbg(ec->dev, "EC does not respond to this command\n"); 135 return 0; 136 } 137 138 /* Wait for it to complete */ 139 if (wilco_ec_response_timed_out(ec)) { 140 dev_dbg(ec->dev, "response timed out\n"); 141 return -ETIMEDOUT; 142 } 143 144 /* Check result */ 145 flag = inb(ec->io_data->start); 146 if (flag) { 147 dev_dbg(ec->dev, "bad response: 0x%02x\n", flag); 148 return -EIO; 149 } 150 151 /* 152 * The EC always returns either EC_MAILBOX_DATA_SIZE or 153 * EC_MAILBOX_DATA_SIZE_EXTENDED bytes of data, so we need to 154 * calculate the checksum on **all** of this data, even if we 155 * won't use all of it. 156 */ 157 if (msg->flags & WILCO_EC_FLAG_EXTENDED_DATA) 158 size = EC_MAILBOX_DATA_SIZE_EXTENDED; 159 else 160 size = EC_MAILBOX_DATA_SIZE; 161 162 /* Read back response */ 163 rs = ec->data_buffer; 164 checksum = cros_ec_lpc_io_bytes_mec(MEC_IO_READ, 0, 165 sizeof(*rs) + size, (u8 *)rs); 166 if (checksum) { 167 dev_dbg(ec->dev, "bad packet checksum 0x%02x\n", rs->checksum); 168 return -EBADMSG; 169 } 170 171 if (rs->result) { 172 dev_dbg(ec->dev, "EC reported failure: 0x%02x\n", rs->result); 173 return -EBADMSG; 174 } 175 176 if (rs->data_size != size) { 177 dev_dbg(ec->dev, "unexpected packet size (%u != %zu)", 178 rs->data_size, size); 179 return -EMSGSIZE; 180 } 181 182 if (rs->data_size < msg->response_size) { 183 dev_dbg(ec->dev, "EC didn't return enough data (%u < %zu)", 184 rs->data_size, msg->response_size); 185 return -EMSGSIZE; 186 } 187 188 memcpy(msg->response_data, rs->data, msg->response_size); 189 190 return rs->data_size; 191 } 192 193 /** 194 * wilco_ec_mailbox() - Send EC request and receive EC response. 195 * @ec: EC device. 196 * @msg: EC message data for request and response. 197 * 198 * On entry msg->type, msg->request_size, and msg->request_data should all be 199 * filled in. If desired, msg->flags can be set. 200 * 201 * If a response is expected, msg->response_size should be set, and 202 * msg->response_data should point to a buffer with enough space. On exit 203 * msg->response_data will be filled. 204 * 205 * Return: number of bytes received or negative error code on failure. 206 */ 207 int wilco_ec_mailbox(struct wilco_ec_device *ec, struct wilco_ec_message *msg) 208 { 209 struct wilco_ec_request *rq; 210 int ret; 211 212 dev_dbg(ec->dev, "type=%04x flags=%02x rslen=%zu rqlen=%zu\n", 213 msg->type, msg->flags, msg->response_size, msg->request_size); 214 215 mutex_lock(&ec->mailbox_lock); 216 /* Prepare request packet */ 217 rq = ec->data_buffer; 218 wilco_ec_prepare(msg, rq); 219 220 ret = wilco_ec_transfer(ec, msg, rq); 221 mutex_unlock(&ec->mailbox_lock); 222 223 return ret; 224 225 } 226 EXPORT_SYMBOL_GPL(wilco_ec_mailbox); 227