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