drivers/platform/chrome/wilco_ec/mailbox.c

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