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 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(port: ec->io_command->start) & |
59 | (EC_CMDR_PENDING | EC_CMDR_BUSY))) |
60 | return false; |
61 | usleep_range(min: 100, max: 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(data: rq, size: sizeof(*rq)); |
102 | rq->checksum += wilco_ec_checksum(data: msg->request_data, size: 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(io_type: MEC_IO_WRITE, offset: 0, length: sizeof(*rq), buf: (u8 *)rq); |
125 | cros_ec_lpc_io_bytes_mec(io_type: MEC_IO_WRITE, offset: sizeof(*rq), length: msg->request_size, |
126 | buf: msg->request_data); |
127 | |
128 | /* Start the command */ |
129 | outb(EC_MAILBOX_START_COMMAND, port: 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(port: 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(io_type: MEC_IO_READ, offset: 0, |
153 | length: sizeof(*rs) + EC_MAILBOX_DATA_SIZE, |
154 | buf: (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(lock: &ec->mailbox_lock); |
211 | |
212 | return ret; |
213 | |
214 | } |
215 | EXPORT_SYMBOL_GPL(wilco_ec_mailbox); |
216 | |