xref: /openbmc/linux/drivers/spi/spi-mt7621.c (revision f125e2d4) 
1 // SPDX-License-Identifier: GPL-2.0
2 //
3 // spi-mt7621.c -- MediaTek MT7621 SPI controller driver
4 //
5 // Copyright (C) 2011 Sergiy <piratfm@gmail.com>
6 // Copyright (C) 2011-2013 Gabor Juhos <juhosg@openwrt.org>
7 // Copyright (C) 2014-2015 Felix Fietkau <nbd@nbd.name>
8 //
9 // Some parts are based on spi-orion.c:
10 //   Author: Shadi Ammouri <shadi@marvell.com>
11 //   Copyright (C) 2007-2008 Marvell Ltd.
12 
13 #include <linux/clk.h>
14 #include <linux/delay.h>
15 #include <linux/io.h>
16 #include <linux/module.h>
17 #include <linux/of_device.h>
18 #include <linux/reset.h>
19 #include <linux/spi/spi.h>
20 
21 #define DRIVER_NAME		"spi-mt7621"
22 
23 /* in usec */
24 #define RALINK_SPI_WAIT_MAX_LOOP 2000
25 
26 /* SPISTAT register bit field */
27 #define SPISTAT_BUSY		BIT(0)
28 
29 #define MT7621_SPI_TRANS	0x00
30 #define SPITRANS_BUSY		BIT(16)
31 
32 #define MT7621_SPI_OPCODE	0x04
33 #define MT7621_SPI_DATA0	0x08
34 #define MT7621_SPI_DATA4	0x18
35 #define SPI_CTL_TX_RX_CNT_MASK	0xff
36 #define SPI_CTL_START		BIT(8)
37 
38 #define MT7621_SPI_MASTER	0x28
39 #define MASTER_MORE_BUFMODE	BIT(2)
40 #define MASTER_FULL_DUPLEX	BIT(10)
41 #define MASTER_RS_CLK_SEL	GENMASK(27, 16)
42 #define MASTER_RS_CLK_SEL_SHIFT	16
43 #define MASTER_RS_SLAVE_SEL	GENMASK(31, 29)
44 
45 #define MT7621_SPI_MOREBUF	0x2c
46 #define MT7621_SPI_POLAR	0x38
47 #define MT7621_SPI_SPACE	0x3c
48 
49 #define MT7621_CPHA		BIT(5)
50 #define MT7621_CPOL		BIT(4)
51 #define MT7621_LSB_FIRST	BIT(3)
52 
53 struct mt7621_spi {
54 	struct spi_controller	*master;
55 	void __iomem		*base;
56 	unsigned int		sys_freq;
57 	unsigned int		speed;
58 	struct clk		*clk;
59 	int			pending_write;
60 };
61 
62 static inline struct mt7621_spi *spidev_to_mt7621_spi(struct spi_device *spi)
63 {
64 	return spi_controller_get_devdata(spi->master);
65 }
66 
67 static inline u32 mt7621_spi_read(struct mt7621_spi *rs, u32 reg)
68 {
69 	return ioread32(rs->base + reg);
70 }
71 
72 static inline void mt7621_spi_write(struct mt7621_spi *rs, u32 reg, u32 val)
73 {
74 	iowrite32(val, rs->base + reg);
75 }
76 
77 static void mt7621_spi_set_cs(struct spi_device *spi, int enable)
78 {
79 	struct mt7621_spi *rs = spidev_to_mt7621_spi(spi);
80 	int cs = spi->chip_select;
81 	u32 polar = 0;
82 	u32 master;
83 
84 	/*
85 	 * Select SPI device 7, enable "more buffer mode" and disable
86 	 * full-duplex (only half-duplex really works on this chip
87 	 * reliably)
88 	 */
89 	master = mt7621_spi_read(rs, MT7621_SPI_MASTER);
90 	master |= MASTER_RS_SLAVE_SEL | MASTER_MORE_BUFMODE;
91 	master &= ~MASTER_FULL_DUPLEX;
92 	mt7621_spi_write(rs, MT7621_SPI_MASTER, master);
93 
94 	rs->pending_write = 0;
95 
96 	if (enable)
97 		polar = BIT(cs);
98 	mt7621_spi_write(rs, MT7621_SPI_POLAR, polar);
99 }
100 
101 static int mt7621_spi_prepare(struct spi_device *spi, unsigned int speed)
102 {
103 	struct mt7621_spi *rs = spidev_to_mt7621_spi(spi);
104 	u32 rate;
105 	u32 reg;
106 
107 	dev_dbg(&spi->dev, "speed:%u\n", speed);
108 
109 	rate = DIV_ROUND_UP(rs->sys_freq, speed);
110 	dev_dbg(&spi->dev, "rate-1:%u\n", rate);
111 
112 	if (rate > 4097)
113 		return -EINVAL;
114 
115 	if (rate < 2)
116 		rate = 2;
117 
118 	reg = mt7621_spi_read(rs, MT7621_SPI_MASTER);
119 	reg &= ~MASTER_RS_CLK_SEL;
120 	reg |= (rate - 2) << MASTER_RS_CLK_SEL_SHIFT;
121 	rs->speed = speed;
122 
123 	reg &= ~MT7621_LSB_FIRST;
124 	if (spi->mode & SPI_LSB_FIRST)
125 		reg |= MT7621_LSB_FIRST;
126 
127 	/*
128 	 * This SPI controller seems to be tested on SPI flash only and some
129 	 * bits are swizzled under other SPI modes probably due to incorrect
130 	 * wiring inside the silicon. Only mode 0 works correctly.
131 	 */
132 	reg &= ~(MT7621_CPHA | MT7621_CPOL);
133 
134 	mt7621_spi_write(rs, MT7621_SPI_MASTER, reg);
135 
136 	return 0;
137 }
138 
139 static inline int mt7621_spi_wait_till_ready(struct mt7621_spi *rs)
140 {
141 	int i;
142 
143 	for (i = 0; i < RALINK_SPI_WAIT_MAX_LOOP; i++) {
144 		u32 status;
145 
146 		status = mt7621_spi_read(rs, MT7621_SPI_TRANS);
147 		if ((status & SPITRANS_BUSY) == 0)
148 			return 0;
149 		cpu_relax();
150 		udelay(1);
151 	}
152 
153 	return -ETIMEDOUT;
154 }
155 
156 static void mt7621_spi_read_half_duplex(struct mt7621_spi *rs,
157 					int rx_len, u8 *buf)
158 {
159 	int tx_len;
160 
161 	/*
162 	 * Combine with any pending write, and perform one or more half-duplex
163 	 * transactions reading 'len' bytes. Data to be written is already in
164 	 * MT7621_SPI_DATA.
165 	 */
166 	tx_len = rs->pending_write;
167 	rs->pending_write = 0;
168 
169 	while (rx_len || tx_len) {
170 		int i;
171 		u32 val = (min(tx_len, 4) * 8) << 24;
172 		int rx = min(rx_len, 32);
173 
174 		if (tx_len > 4)
175 			val |= (tx_len - 4) * 8;
176 		val |= (rx * 8) << 12;
177 		mt7621_spi_write(rs, MT7621_SPI_MOREBUF, val);
178 
179 		tx_len = 0;
180 
181 		val = mt7621_spi_read(rs, MT7621_SPI_TRANS);
182 		val |= SPI_CTL_START;
183 		mt7621_spi_write(rs, MT7621_SPI_TRANS, val);
184 
185 		mt7621_spi_wait_till_ready(rs);
186 
187 		for (i = 0; i < rx; i++) {
188 			if ((i % 4) == 0)
189 				val = mt7621_spi_read(rs, MT7621_SPI_DATA0 + i);
190 			*buf++ = val & 0xff;
191 			val >>= 8;
192 		}
193 
194 		rx_len -= i;
195 	}
196 }
197 
198 static inline void mt7621_spi_flush(struct mt7621_spi *rs)
199 {
200 	mt7621_spi_read_half_duplex(rs, 0, NULL);
201 }
202 
203 static void mt7621_spi_write_half_duplex(struct mt7621_spi *rs,
204 					 int tx_len, const u8 *buf)
205 {
206 	int len = rs->pending_write;
207 	int val = 0;
208 
209 	if (len & 3) {
210 		val = mt7621_spi_read(rs, MT7621_SPI_OPCODE + (len & ~3));
211 		if (len < 4) {
212 			val <<= (4 - len) * 8;
213 			val = swab32(val);
214 		}
215 	}
216 
217 	while (tx_len > 0) {
218 		if (len >= 36) {
219 			rs->pending_write = len;
220 			mt7621_spi_flush(rs);
221 			len = 0;
222 		}
223 
224 		val |= *buf++ << (8 * (len & 3));
225 		len++;
226 		if ((len & 3) == 0) {
227 			if (len == 4)
228 				/* The byte-order of the opcode is weird! */
229 				val = swab32(val);
230 			mt7621_spi_write(rs, MT7621_SPI_OPCODE + len - 4, val);
231 			val = 0;
232 		}
233 		tx_len -= 1;
234 	}
235 
236 	if (len & 3) {
237 		if (len < 4) {
238 			val = swab32(val);
239 			val >>= (4 - len) * 8;
240 		}
241 		mt7621_spi_write(rs, MT7621_SPI_OPCODE + (len & ~3), val);
242 	}
243 
244 	rs->pending_write = len;
245 }
246 
247 static int mt7621_spi_transfer_one_message(struct spi_controller *master,
248 					   struct spi_message *m)
249 {
250 	struct mt7621_spi *rs = spi_controller_get_devdata(master);
251 	struct spi_device *spi = m->spi;
252 	unsigned int speed = spi->max_speed_hz;
253 	struct spi_transfer *t = NULL;
254 	int status = 0;
255 
256 	mt7621_spi_wait_till_ready(rs);
257 
258 	list_for_each_entry(t, &m->transfers, transfer_list)
259 		if (t->speed_hz < speed)
260 			speed = t->speed_hz;
261 
262 	if (mt7621_spi_prepare(spi, speed)) {
263 		status = -EIO;
264 		goto msg_done;
265 	}
266 
267 	/* Assert CS */
268 	mt7621_spi_set_cs(spi, 1);
269 
270 	m->actual_length = 0;
271 	list_for_each_entry(t, &m->transfers, transfer_list) {
272 		if ((t->rx_buf) && (t->tx_buf)) {
273 			/*
274 			 * This controller will shift some extra data out
275 			 * of spi_opcode if (mosi_bit_cnt > 0) &&
276 			 * (cmd_bit_cnt == 0). So the claimed full-duplex
277 			 * support is broken since we have no way to read
278 			 * the MISO value during that bit.
279 			 */
280 			status = -EIO;
281 			goto msg_done;
282 		} else if (t->rx_buf) {
283 			mt7621_spi_read_half_duplex(rs, t->len, t->rx_buf);
284 		} else if (t->tx_buf) {
285 			mt7621_spi_write_half_duplex(rs, t->len, t->tx_buf);
286 		}
287 		m->actual_length += t->len;
288 	}
289 
290 	/* Flush data and deassert CS */
291 	mt7621_spi_flush(rs);
292 	mt7621_spi_set_cs(spi, 0);
293 
294 msg_done:
295 	m->status = status;
296 	spi_finalize_current_message(master);
297 
298 	return 0;
299 }
300 
301 static int mt7621_spi_setup(struct spi_device *spi)
302 {
303 	struct mt7621_spi *rs = spidev_to_mt7621_spi(spi);
304 
305 	if ((spi->max_speed_hz == 0) ||
306 	    (spi->max_speed_hz > (rs->sys_freq / 2)))
307 		spi->max_speed_hz = rs->sys_freq / 2;
308 
309 	if (spi->max_speed_hz < (rs->sys_freq / 4097)) {
310 		dev_err(&spi->dev, "setup: requested speed is too low %d Hz\n",
311 			spi->max_speed_hz);
312 		return -EINVAL;
313 	}
314 
315 	return 0;
316 }
317 
318 static const struct of_device_id mt7621_spi_match[] = {
319 	{ .compatible = "ralink,mt7621-spi" },
320 	{},
321 };
322 MODULE_DEVICE_TABLE(of, mt7621_spi_match);
323 
324 static int mt7621_spi_probe(struct platform_device *pdev)
325 {
326 	const struct of_device_id *match;
327 	struct spi_controller *master;
328 	struct mt7621_spi *rs;
329 	void __iomem *base;
330 	int status = 0;
331 	struct clk *clk;
332 	int ret;
333 
334 	match = of_match_device(mt7621_spi_match, &pdev->dev);
335 	if (!match)
336 		return -EINVAL;
337 
338 	base = devm_platform_ioremap_resource(pdev, 0);
339 	if (IS_ERR(base))
340 		return PTR_ERR(base);
341 
342 	clk = devm_clk_get(&pdev->dev, NULL);
343 	if (IS_ERR(clk)) {
344 		dev_err(&pdev->dev, "unable to get SYS clock, err=%d\n",
345 			status);
346 		return PTR_ERR(clk);
347 	}
348 
349 	status = clk_prepare_enable(clk);
350 	if (status)
351 		return status;
352 
353 	master = spi_alloc_master(&pdev->dev, sizeof(*rs));
354 	if (!master) {
355 		dev_info(&pdev->dev, "master allocation failed\n");
356 		return -ENOMEM;
357 	}
358 
359 	master->mode_bits = SPI_LSB_FIRST;
360 	master->flags = SPI_CONTROLLER_HALF_DUPLEX;
361 	master->setup = mt7621_spi_setup;
362 	master->transfer_one_message = mt7621_spi_transfer_one_message;
363 	master->bits_per_word_mask = SPI_BPW_MASK(8);
364 	master->dev.of_node = pdev->dev.of_node;
365 	master->num_chipselect = 2;
366 
367 	dev_set_drvdata(&pdev->dev, master);
368 
369 	rs = spi_controller_get_devdata(master);
370 	rs->base = base;
371 	rs->clk = clk;
372 	rs->master = master;
373 	rs->sys_freq = clk_get_rate(rs->clk);
374 	rs->pending_write = 0;
375 	dev_info(&pdev->dev, "sys_freq: %u\n", rs->sys_freq);
376 
377 	ret = device_reset(&pdev->dev);
378 	if (ret) {
379 		dev_err(&pdev->dev, "SPI reset failed!\n");
380 		return ret;
381 	}
382 
383 	return devm_spi_register_controller(&pdev->dev, master);
384 }
385 
386 static int mt7621_spi_remove(struct platform_device *pdev)
387 {
388 	struct spi_controller *master;
389 	struct mt7621_spi *rs;
390 
391 	master = dev_get_drvdata(&pdev->dev);
392 	rs = spi_controller_get_devdata(master);
393 
394 	clk_disable_unprepare(rs->clk);
395 
396 	return 0;
397 }
398 
399 MODULE_ALIAS("platform:" DRIVER_NAME);
400 
401 static struct platform_driver mt7621_spi_driver = {
402 	.driver = {
403 		.name = DRIVER_NAME,
404 		.of_match_table = mt7621_spi_match,
405 	},
406 	.probe = mt7621_spi_probe,
407 	.remove = mt7621_spi_remove,
408 };
409 
410 module_platform_driver(mt7621_spi_driver);
411 
412 MODULE_DESCRIPTION("MT7621 SPI driver");
413 MODULE_AUTHOR("Felix Fietkau <nbd@nbd.name>");
414 MODULE_LICENSE("GPL");
415