1/*
2 * NXP SC18IS602/603 SPI driver
3 *
4 * Copyright (C) Guenter Roeck <linux@roeck-us.net>
5 *
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License as published by
8 * the Free Software Foundation; either version 2 of the License, or
9 * (at your option) any later version.
10 *
11 * This program is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
14 * GNU General Public License for more details.
15 */
16
17#include <linux/kernel.h>
18#include <linux/err.h>
19#include <linux/module.h>
20#include <linux/spi/spi.h>
21#include <linux/i2c.h>
22#include <linux/delay.h>
23#include <linux/pm_runtime.h>
24#include <linux/of.h>
25#include <linux/platform_data/sc18is602.h>
26
27enum chips { sc18is602, sc18is602b, sc18is603 };
28
29#define SC18IS602_BUFSIZ		200
30#define SC18IS602_CLOCK			7372000
31
32#define SC18IS602_MODE_CPHA		BIT(2)
33#define SC18IS602_MODE_CPOL		BIT(3)
34#define SC18IS602_MODE_LSB_FIRST	BIT(5)
35#define SC18IS602_MODE_CLOCK_DIV_4	0x0
36#define SC18IS602_MODE_CLOCK_DIV_16	0x1
37#define SC18IS602_MODE_CLOCK_DIV_64	0x2
38#define SC18IS602_MODE_CLOCK_DIV_128	0x3
39
40struct sc18is602 {
41	struct spi_master	*master;
42	struct device		*dev;
43	u8			ctrl;
44	u32			freq;
45	u32			speed;
46
47	/* I2C data */
48	struct i2c_client	*client;
49	enum chips		id;
50	u8			buffer[SC18IS602_BUFSIZ + 1];
51	int			tlen;	/* Data queued for tx in buffer */
52	int			rindex;	/* Receive data index in buffer */
53};
54
55static int sc18is602_wait_ready(struct sc18is602 *hw, int len)
56{
57	int i, err;
58	int usecs = 1000000 * len / hw->speed + 1;
59	u8 dummy[1];
60
61	for (i = 0; i < 10; i++) {
62		err = i2c_master_recv(hw->client, dummy, 1);
63		if (err >= 0)
64			return 0;
65		usleep_range(usecs, usecs * 2);
66	}
67	return -ETIMEDOUT;
68}
69
70static int sc18is602_txrx(struct sc18is602 *hw, struct spi_message *msg,
71			  struct spi_transfer *t, bool do_transfer)
72{
73	unsigned int len = t->len;
74	int ret;
75
76	if (hw->tlen == 0) {
77		/* First byte (I2C command) is chip select */
78		hw->buffer[0] = 1 << msg->spi->chip_select;
79		hw->tlen = 1;
80		hw->rindex = 0;
81	}
82	/*
83	 * We can not immediately send data to the chip, since each I2C message
84	 * resembles a full SPI message (from CS active to CS inactive).
85	 * Enqueue messages up to the first read or until do_transfer is true.
86	 */
87	if (t->tx_buf) {
88		memcpy(&hw->buffer[hw->tlen], t->tx_buf, len);
89		hw->tlen += len;
90		if (t->rx_buf)
91			do_transfer = true;
92		else
93			hw->rindex = hw->tlen - 1;
94	} else if (t->rx_buf) {
95		/*
96		 * For receive-only transfers we still need to perform a dummy
97		 * write to receive data from the SPI chip.
98		 * Read data starts at the end of transmit data (minus 1 to
99		 * account for CS).
100		 */
101		hw->rindex = hw->tlen - 1;
102		memset(&hw->buffer[hw->tlen], 0, len);
103		hw->tlen += len;
104		do_transfer = true;
105	}
106
107	if (do_transfer && hw->tlen > 1) {
108		ret = sc18is602_wait_ready(hw, SC18IS602_BUFSIZ);
109		if (ret < 0)
110			return ret;
111		ret = i2c_master_send(hw->client, hw->buffer, hw->tlen);
112		if (ret < 0)
113			return ret;
114		if (ret != hw->tlen)
115			return -EIO;
116
117		if (t->rx_buf) {
118			int rlen = hw->rindex + len;
119
120			ret = sc18is602_wait_ready(hw, hw->tlen);
121			if (ret < 0)
122				return ret;
123			ret = i2c_master_recv(hw->client, hw->buffer, rlen);
124			if (ret < 0)
125				return ret;
126			if (ret != rlen)
127				return -EIO;
128			memcpy(t->rx_buf, &hw->buffer[hw->rindex], len);
129		}
130		hw->tlen = 0;
131	}
132	return len;
133}
134
135static int sc18is602_setup_transfer(struct sc18is602 *hw, u32 hz, u8 mode)
136{
137	u8 ctrl = 0;
138	int ret;
139
140	if (mode & SPI_CPHA)
141		ctrl |= SC18IS602_MODE_CPHA;
142	if (mode & SPI_CPOL)
143		ctrl |= SC18IS602_MODE_CPOL;
144	if (mode & SPI_LSB_FIRST)
145		ctrl |= SC18IS602_MODE_LSB_FIRST;
146
147	/* Find the closest clock speed */
148	if (hz >= hw->freq / 4) {
149		ctrl |= SC18IS602_MODE_CLOCK_DIV_4;
150		hw->speed = hw->freq / 4;
151	} else if (hz >= hw->freq / 16) {
152		ctrl |= SC18IS602_MODE_CLOCK_DIV_16;
153		hw->speed = hw->freq / 16;
154	} else if (hz >= hw->freq / 64) {
155		ctrl |= SC18IS602_MODE_CLOCK_DIV_64;
156		hw->speed = hw->freq / 64;
157	} else {
158		ctrl |= SC18IS602_MODE_CLOCK_DIV_128;
159		hw->speed = hw->freq / 128;
160	}
161
162	/*
163	 * Don't do anything if the control value did not change. The initial
164	 * value of 0xff for hw->ctrl ensures that the correct mode will be set
165	 * with the first call to this function.
166	 */
167	if (ctrl == hw->ctrl)
168		return 0;
169
170	ret = i2c_smbus_write_byte_data(hw->client, 0xf0, ctrl);
171	if (ret < 0)
172		return ret;
173
174	hw->ctrl = ctrl;
175
176	return 0;
177}
178
179static int sc18is602_check_transfer(struct spi_device *spi,
180				    struct spi_transfer *t, int tlen)
181{
182	if (t && t->len + tlen > SC18IS602_BUFSIZ)
183		return -EINVAL;
184
185	return 0;
186}
187
188static int sc18is602_transfer_one(struct spi_master *master,
189				  struct spi_message *m)
190{
191	struct sc18is602 *hw = spi_master_get_devdata(master);
192	struct spi_device *spi = m->spi;
193	struct spi_transfer *t;
194	int status = 0;
195
196	hw->tlen = 0;
197	list_for_each_entry(t, &m->transfers, transfer_list) {
198		bool do_transfer;
199
200		status = sc18is602_check_transfer(spi, t, hw->tlen);
201		if (status < 0)
202			break;
203
204		status = sc18is602_setup_transfer(hw, t->speed_hz, spi->mode);
205		if (status < 0)
206			break;
207
208		do_transfer = t->cs_change || list_is_last(&t->transfer_list,
209							   &m->transfers);
210
211		if (t->len) {
212			status = sc18is602_txrx(hw, m, t, do_transfer);
213			if (status < 0)
214				break;
215			m->actual_length += status;
216		}
217		status = 0;
218
219		if (t->delay_usecs)
220			udelay(t->delay_usecs);
221	}
222	m->status = status;
223	spi_finalize_current_message(master);
224
225	return status;
226}
227
228static int sc18is602_setup(struct spi_device *spi)
229{
230	struct sc18is602 *hw = spi_master_get_devdata(spi->master);
231
232	/* SC18IS602 does not support CS2 */
233	if (hw->id == sc18is602 && spi->chip_select == 2)
234		return -ENXIO;
235
236	return 0;
237}
238
239static int sc18is602_probe(struct i2c_client *client,
240			   const struct i2c_device_id *id)
241{
242	struct device *dev = &client->dev;
243	struct device_node *np = dev->of_node;
244	struct sc18is602_platform_data *pdata = dev_get_platdata(dev);
245	struct sc18is602 *hw;
246	struct spi_master *master;
247	int error;
248
249	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C |
250				     I2C_FUNC_SMBUS_WRITE_BYTE_DATA))
251		return -EINVAL;
252
253	master = spi_alloc_master(dev, sizeof(struct sc18is602));
254	if (!master)
255		return -ENOMEM;
256
257	hw = spi_master_get_devdata(master);
258	i2c_set_clientdata(client, hw);
259
260	hw->master = master;
261	hw->client = client;
262	hw->dev = dev;
263	hw->ctrl = 0xff;
264
265	hw->id = id->driver_data;
266
267	switch (hw->id) {
268	case sc18is602:
269	case sc18is602b:
270		master->num_chipselect = 4;
271		hw->freq = SC18IS602_CLOCK;
272		break;
273	case sc18is603:
274		master->num_chipselect = 2;
275		if (pdata) {
276			hw->freq = pdata->clock_frequency;
277		} else {
278			const __be32 *val;
279			int len;
280
281			val = of_get_property(np, "clock-frequency", &len);
282			if (val && len >= sizeof(__be32))
283				hw->freq = be32_to_cpup(val);
284		}
285		if (!hw->freq)
286			hw->freq = SC18IS602_CLOCK;
287		break;
288	}
289	master->bus_num = np ? -1 : client->adapter->nr;
290	master->mode_bits = SPI_CPHA | SPI_CPOL | SPI_LSB_FIRST;
291	master->bits_per_word_mask = SPI_BPW_MASK(8);
292	master->setup = sc18is602_setup;
293	master->transfer_one_message = sc18is602_transfer_one;
294	master->dev.of_node = np;
295	master->min_speed_hz = hw->freq / 128;
296	master->max_speed_hz = hw->freq / 4;
297
298	error = devm_spi_register_master(dev, master);
299	if (error)
300		goto error_reg;
301
302	return 0;
303
304error_reg:
305	spi_master_put(master);
306	return error;
307}
308
309static const struct i2c_device_id sc18is602_id[] = {
310	{ "sc18is602", sc18is602 },
311	{ "sc18is602b", sc18is602b },
312	{ "sc18is603", sc18is603 },
313	{ }
314};
315MODULE_DEVICE_TABLE(i2c, sc18is602_id);
316
317static struct i2c_driver sc18is602_driver = {
318	.driver = {
319		.name = "sc18is602",
320	},
321	.probe = sc18is602_probe,
322	.id_table = sc18is602_id,
323};
324
325module_i2c_driver(sc18is602_driver);
326
327MODULE_DESCRIPTION("SC18IC602/603 SPI Master Driver");
328MODULE_AUTHOR("Guenter Roeck");
329MODULE_LICENSE("GPL");
330