1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * I2C slave mode testunit
4  *
5  * Copyright (C) 2020 by Wolfram Sang, Sang Engineering <wsa@sang-engineering.com>
6  * Copyright (C) 2020 by Renesas Electronics Corporation
7  */
8 
9 #include <linux/bitops.h>
10 #include <linux/i2c.h>
11 #include <linux/init.h>
12 #include <linux/module.h>
13 #include <linux/of.h>
14 #include <linux/slab.h>
15 #include <linux/workqueue.h> /* FIXME: is system_long_wq the best choice? */
16 
17 #define TU_CUR_VERSION 0x01
18 
19 enum testunit_cmds {
20 	TU_CMD_READ_BYTES = 1,	/* save 0 for ABORT, RESET or similar */
21 	TU_CMD_HOST_NOTIFY,
22 	TU_CMD_SMBUS_BLOCK_PROC_CALL,
23 	TU_NUM_CMDS
24 };
25 
26 enum testunit_regs {
27 	TU_REG_CMD,
28 	TU_REG_DATAL,
29 	TU_REG_DATAH,
30 	TU_REG_DELAY,
31 	TU_NUM_REGS
32 };
33 
34 enum testunit_flags {
35 	TU_FLAG_IN_PROCESS,
36 };
37 
38 struct testunit_data {
39 	unsigned long flags;
40 	u8 regs[TU_NUM_REGS];
41 	u8 reg_idx;
42 	struct i2c_client *client;
43 	struct delayed_work worker;
44 };
45 
46 static void i2c_slave_testunit_work(struct work_struct *work)
47 {
48 	struct testunit_data *tu = container_of(work, struct testunit_data, worker.work);
49 	struct i2c_msg msg;
50 	u8 msgbuf[256];
51 	int ret = 0;
52 
53 	msg.addr = I2C_CLIENT_END;
54 	msg.buf = msgbuf;
55 
56 	switch (tu->regs[TU_REG_CMD]) {
57 	case TU_CMD_READ_BYTES:
58 		msg.addr = tu->regs[TU_REG_DATAL];
59 		msg.flags = I2C_M_RD;
60 		msg.len = tu->regs[TU_REG_DATAH];
61 		break;
62 
63 	case TU_CMD_HOST_NOTIFY:
64 		msg.addr = 0x08;
65 		msg.flags = 0;
66 		msg.len = 3;
67 		msgbuf[0] = tu->client->addr;
68 		msgbuf[1] = tu->regs[TU_REG_DATAL];
69 		msgbuf[2] = tu->regs[TU_REG_DATAH];
70 		break;
71 
72 	default:
73 		break;
74 	}
75 
76 	if (msg.addr != I2C_CLIENT_END) {
77 		ret = i2c_transfer(tu->client->adapter, &msg, 1);
78 		/* convert '0 msgs transferred' to errno */
79 		ret = (ret == 0) ? -EIO : ret;
80 	}
81 
82 	if (ret < 0)
83 		dev_err(&tu->client->dev, "CMD%02X failed (%d)\n", tu->regs[TU_REG_CMD], ret);
84 
85 	clear_bit(TU_FLAG_IN_PROCESS, &tu->flags);
86 }
87 
88 static int i2c_slave_testunit_slave_cb(struct i2c_client *client,
89 				     enum i2c_slave_event event, u8 *val)
90 {
91 	struct testunit_data *tu = i2c_get_clientdata(client);
92 	bool is_proc_call = tu->reg_idx == 3 && tu->regs[TU_REG_DATAL] == 1 &&
93 			    tu->regs[TU_REG_CMD] == TU_CMD_SMBUS_BLOCK_PROC_CALL;
94 	int ret = 0;
95 
96 	switch (event) {
97 	case I2C_SLAVE_WRITE_RECEIVED:
98 		if (test_bit(TU_FLAG_IN_PROCESS, &tu->flags))
99 			return -EBUSY;
100 
101 		if (tu->reg_idx < TU_NUM_REGS)
102 			tu->regs[tu->reg_idx] = *val;
103 		else
104 			ret = -EMSGSIZE;
105 
106 		if (tu->reg_idx <= TU_NUM_REGS)
107 			tu->reg_idx++;
108 
109 		/* TU_REG_CMD always written at this point */
110 		if (tu->regs[TU_REG_CMD] >= TU_NUM_CMDS)
111 			ret = -EINVAL;
112 
113 		break;
114 
115 	case I2C_SLAVE_STOP:
116 		if (tu->reg_idx == TU_NUM_REGS) {
117 			set_bit(TU_FLAG_IN_PROCESS, &tu->flags);
118 			queue_delayed_work(system_long_wq, &tu->worker,
119 					   msecs_to_jiffies(10 * tu->regs[TU_REG_DELAY]));
120 		}
121 		fallthrough;
122 
123 	case I2C_SLAVE_WRITE_REQUESTED:
124 		memset(tu->regs, 0, TU_NUM_REGS);
125 		tu->reg_idx = 0;
126 		break;
127 
128 	case I2C_SLAVE_READ_PROCESSED:
129 		if (is_proc_call && tu->regs[TU_REG_DATAH])
130 			tu->regs[TU_REG_DATAH]--;
131 		fallthrough;
132 
133 	case I2C_SLAVE_READ_REQUESTED:
134 		*val = is_proc_call ? tu->regs[TU_REG_DATAH] : TU_CUR_VERSION;
135 		break;
136 	}
137 
138 	return ret;
139 }
140 
141 static int i2c_slave_testunit_probe(struct i2c_client *client)
142 {
143 	struct testunit_data *tu;
144 
145 	tu = devm_kzalloc(&client->dev, sizeof(struct testunit_data), GFP_KERNEL);
146 	if (!tu)
147 		return -ENOMEM;
148 
149 	tu->client = client;
150 	i2c_set_clientdata(client, tu);
151 	INIT_DELAYED_WORK(&tu->worker, i2c_slave_testunit_work);
152 
153 	return i2c_slave_register(client, i2c_slave_testunit_slave_cb);
154 };
155 
156 static void i2c_slave_testunit_remove(struct i2c_client *client)
157 {
158 	struct testunit_data *tu = i2c_get_clientdata(client);
159 
160 	cancel_delayed_work_sync(&tu->worker);
161 	i2c_slave_unregister(client);
162 }
163 
164 static const struct i2c_device_id i2c_slave_testunit_id[] = {
165 	{ "slave-testunit", 0 },
166 	{ }
167 };
168 MODULE_DEVICE_TABLE(i2c, i2c_slave_testunit_id);
169 
170 static struct i2c_driver i2c_slave_testunit_driver = {
171 	.driver = {
172 		.name = "i2c-slave-testunit",
173 	},
174 	.probe = i2c_slave_testunit_probe,
175 	.remove = i2c_slave_testunit_remove,
176 	.id_table = i2c_slave_testunit_id,
177 };
178 module_i2c_driver(i2c_slave_testunit_driver);
179 
180 MODULE_AUTHOR("Wolfram Sang <wsa@sang-engineering.com>");
181 MODULE_DESCRIPTION("I2C slave mode test unit");
182 MODULE_LICENSE("GPL v2");
183