xref: /openbmc/linux/drivers/spi/spi-st-ssc4.c (revision 82e6fdd6) 
1 /*
2  *  Copyright (c) 2008-2014 STMicroelectronics Limited
3  *
4  *  Author: Angus Clark <Angus.Clark@st.com>
5  *          Patrice Chotard <patrice.chotard@st.com>
6  *          Lee Jones <lee.jones@linaro.org>
7  *
8  *  SPI master mode controller driver, used in STMicroelectronics devices.
9  *
10  *  May be copied or modified under the terms of the GNU General Public
11  *  License Version 2.0 only.  See linux/COPYING for more information.
12  */
13 
14 #include <linux/clk.h>
15 #include <linux/delay.h>
16 #include <linux/interrupt.h>
17 #include <linux/io.h>
18 #include <linux/module.h>
19 #include <linux/pinctrl/consumer.h>
20 #include <linux/platform_device.h>
21 #include <linux/of.h>
22 #include <linux/of_gpio.h>
23 #include <linux/of_irq.h>
24 #include <linux/pm_runtime.h>
25 #include <linux/spi/spi.h>
26 #include <linux/spi/spi_bitbang.h>
27 
28 /* SSC registers */
29 #define SSC_BRG				0x000
30 #define SSC_TBUF			0x004
31 #define SSC_RBUF			0x008
32 #define SSC_CTL				0x00C
33 #define SSC_IEN				0x010
34 #define SSC_I2C				0x018
35 
36 /* SSC Control */
37 #define SSC_CTL_DATA_WIDTH_9		0x8
38 #define SSC_CTL_DATA_WIDTH_MSK		0xf
39 #define SSC_CTL_BM			0xf
40 #define SSC_CTL_HB			BIT(4)
41 #define SSC_CTL_PH			BIT(5)
42 #define SSC_CTL_PO			BIT(6)
43 #define SSC_CTL_SR			BIT(7)
44 #define SSC_CTL_MS			BIT(8)
45 #define SSC_CTL_EN			BIT(9)
46 #define SSC_CTL_LPB			BIT(10)
47 #define SSC_CTL_EN_TX_FIFO		BIT(11)
48 #define SSC_CTL_EN_RX_FIFO		BIT(12)
49 #define SSC_CTL_EN_CLST_RX		BIT(13)
50 
51 /* SSC Interrupt Enable */
52 #define SSC_IEN_TEEN			BIT(2)
53 
54 #define FIFO_SIZE			8
55 
56 struct spi_st {
57 	/* SSC SPI Controller */
58 	void __iomem		*base;
59 	struct clk		*clk;
60 	struct device		*dev;
61 
62 	/* SSC SPI current transaction */
63 	const u8		*tx_ptr;
64 	u8			*rx_ptr;
65 	u16			bytes_per_word;
66 	unsigned int		words_remaining;
67 	unsigned int		baud;
68 	struct completion	done;
69 };
70 
71 /* Load the TX FIFO */
72 static void ssc_write_tx_fifo(struct spi_st *spi_st)
73 {
74 	unsigned int count, i;
75 	uint32_t word = 0;
76 
77 	if (spi_st->words_remaining > FIFO_SIZE)
78 		count = FIFO_SIZE;
79 	else
80 		count = spi_st->words_remaining;
81 
82 	for (i = 0; i < count; i++) {
83 		if (spi_st->tx_ptr) {
84 			if (spi_st->bytes_per_word == 1) {
85 				word = *spi_st->tx_ptr++;
86 			} else {
87 				word = *spi_st->tx_ptr++;
88 				word = *spi_st->tx_ptr++ | (word << 8);
89 			}
90 		}
91 		writel_relaxed(word, spi_st->base + SSC_TBUF);
92 	}
93 }
94 
95 /* Read the RX FIFO */
96 static void ssc_read_rx_fifo(struct spi_st *spi_st)
97 {
98 	unsigned int count, i;
99 	uint32_t word = 0;
100 
101 	if (spi_st->words_remaining > FIFO_SIZE)
102 		count = FIFO_SIZE;
103 	else
104 		count = spi_st->words_remaining;
105 
106 	for (i = 0; i < count; i++) {
107 		word = readl_relaxed(spi_st->base + SSC_RBUF);
108 
109 		if (spi_st->rx_ptr) {
110 			if (spi_st->bytes_per_word == 1) {
111 				*spi_st->rx_ptr++ = (uint8_t)word;
112 			} else {
113 				*spi_st->rx_ptr++ = (word >> 8);
114 				*spi_st->rx_ptr++ = word & 0xff;
115 			}
116 		}
117 	}
118 	spi_st->words_remaining -= count;
119 }
120 
121 static int spi_st_transfer_one(struct spi_master *master,
122 			       struct spi_device *spi, struct spi_transfer *t)
123 {
124 	struct spi_st *spi_st = spi_master_get_devdata(master);
125 	uint32_t ctl = 0;
126 
127 	/* Setup transfer */
128 	spi_st->tx_ptr = t->tx_buf;
129 	spi_st->rx_ptr = t->rx_buf;
130 
131 	if (spi->bits_per_word > 8) {
132 		/*
133 		 * Anything greater than 8 bits-per-word requires 2
134 		 * bytes-per-word in the RX/TX buffers
135 		 */
136 		spi_st->bytes_per_word = 2;
137 		spi_st->words_remaining = t->len / 2;
138 
139 	} else if (spi->bits_per_word == 8 && !(t->len & 0x1)) {
140 		/*
141 		 * If transfer is even-length, and 8 bits-per-word, then
142 		 * implement as half-length 16 bits-per-word transfer
143 		 */
144 		spi_st->bytes_per_word = 2;
145 		spi_st->words_remaining = t->len / 2;
146 
147 		/* Set SSC_CTL to 16 bits-per-word */
148 		ctl = readl_relaxed(spi_st->base + SSC_CTL);
149 		writel_relaxed((ctl | 0xf), spi_st->base + SSC_CTL);
150 
151 		readl_relaxed(spi_st->base + SSC_RBUF);
152 
153 	} else {
154 		spi_st->bytes_per_word = 1;
155 		spi_st->words_remaining = t->len;
156 	}
157 
158 	reinit_completion(&spi_st->done);
159 
160 	/* Start transfer by writing to the TX FIFO */
161 	ssc_write_tx_fifo(spi_st);
162 	writel_relaxed(SSC_IEN_TEEN, spi_st->base + SSC_IEN);
163 
164 	/* Wait for transfer to complete */
165 	wait_for_completion(&spi_st->done);
166 
167 	/* Restore SSC_CTL if necessary */
168 	if (ctl)
169 		writel_relaxed(ctl, spi_st->base + SSC_CTL);
170 
171 	spi_finalize_current_transfer(spi->master);
172 
173 	return t->len;
174 }
175 
176 static void spi_st_cleanup(struct spi_device *spi)
177 {
178 	gpio_free(spi->cs_gpio);
179 }
180 
181 /* the spi->mode bits understood by this driver: */
182 #define MODEBITS  (SPI_CPOL | SPI_CPHA | SPI_LSB_FIRST | SPI_LOOP | SPI_CS_HIGH)
183 static int spi_st_setup(struct spi_device *spi)
184 {
185 	struct spi_st *spi_st = spi_master_get_devdata(spi->master);
186 	u32 spi_st_clk, sscbrg, var;
187 	u32 hz = spi->max_speed_hz;
188 	int cs = spi->cs_gpio;
189 	int ret;
190 
191 	if (!hz)  {
192 		dev_err(&spi->dev, "max_speed_hz unspecified\n");
193 		return -EINVAL;
194 	}
195 
196 	if (!gpio_is_valid(cs)) {
197 		dev_err(&spi->dev, "%d is not a valid gpio\n", cs);
198 		return -EINVAL;
199 	}
200 
201 	ret = gpio_request(cs, dev_name(&spi->dev));
202 	if (ret) {
203 		dev_err(&spi->dev, "could not request gpio:%d\n", cs);
204 		return ret;
205 	}
206 
207 	ret = gpio_direction_output(cs, spi->mode & SPI_CS_HIGH);
208 	if (ret)
209 		goto out_free_gpio;
210 
211 	spi_st_clk = clk_get_rate(spi_st->clk);
212 
213 	/* Set SSC_BRF */
214 	sscbrg = spi_st_clk / (2 * hz);
215 	if (sscbrg < 0x07 || sscbrg > BIT(16)) {
216 		dev_err(&spi->dev,
217 			"baudrate %d outside valid range %d\n", sscbrg, hz);
218 		ret = -EINVAL;
219 		goto out_free_gpio;
220 	}
221 
222 	spi_st->baud = spi_st_clk / (2 * sscbrg);
223 	if (sscbrg == BIT(16)) /* 16-bit counter wraps */
224 		sscbrg = 0x0;
225 
226 	writel_relaxed(sscbrg, spi_st->base + SSC_BRG);
227 
228 	dev_dbg(&spi->dev,
229 		"setting baudrate:target= %u hz, actual= %u hz, sscbrg= %u\n",
230 		hz, spi_st->baud, sscbrg);
231 
232 	/* Set SSC_CTL and enable SSC */
233 	var = readl_relaxed(spi_st->base + SSC_CTL);
234 	var |= SSC_CTL_MS;
235 
236 	if (spi->mode & SPI_CPOL)
237 		var |= SSC_CTL_PO;
238 	else
239 		var &= ~SSC_CTL_PO;
240 
241 	if (spi->mode & SPI_CPHA)
242 		var |= SSC_CTL_PH;
243 	else
244 		var &= ~SSC_CTL_PH;
245 
246 	if ((spi->mode & SPI_LSB_FIRST) == 0)
247 		var |= SSC_CTL_HB;
248 	else
249 		var &= ~SSC_CTL_HB;
250 
251 	if (spi->mode & SPI_LOOP)
252 		var |= SSC_CTL_LPB;
253 	else
254 		var &= ~SSC_CTL_LPB;
255 
256 	var &= ~SSC_CTL_DATA_WIDTH_MSK;
257 	var |= (spi->bits_per_word - 1);
258 
259 	var |= SSC_CTL_EN_TX_FIFO | SSC_CTL_EN_RX_FIFO;
260 	var |= SSC_CTL_EN;
261 
262 	writel_relaxed(var, spi_st->base + SSC_CTL);
263 
264 	/* Clear the status register */
265 	readl_relaxed(spi_st->base + SSC_RBUF);
266 
267 	return 0;
268 
269 out_free_gpio:
270 	gpio_free(cs);
271 	return ret;
272 }
273 
274 /* Interrupt fired when TX shift register becomes empty */
275 static irqreturn_t spi_st_irq(int irq, void *dev_id)
276 {
277 	struct spi_st *spi_st = (struct spi_st *)dev_id;
278 
279 	/* Read RX FIFO */
280 	ssc_read_rx_fifo(spi_st);
281 
282 	/* Fill TX FIFO */
283 	if (spi_st->words_remaining) {
284 		ssc_write_tx_fifo(spi_st);
285 	} else {
286 		/* TX/RX complete */
287 		writel_relaxed(0x0, spi_st->base + SSC_IEN);
288 		/*
289 		 * read SSC_IEN to ensure that this bit is set
290 		 * before re-enabling interrupt
291 		 */
292 		readl(spi_st->base + SSC_IEN);
293 		complete(&spi_st->done);
294 	}
295 
296 	return IRQ_HANDLED;
297 }
298 
299 static int spi_st_probe(struct platform_device *pdev)
300 {
301 	struct device_node *np = pdev->dev.of_node;
302 	struct spi_master *master;
303 	struct resource *res;
304 	struct spi_st *spi_st;
305 	int irq, ret = 0;
306 	u32 var;
307 
308 	master = spi_alloc_master(&pdev->dev, sizeof(*spi_st));
309 	if (!master)
310 		return -ENOMEM;
311 
312 	master->dev.of_node		= np;
313 	master->mode_bits		= MODEBITS;
314 	master->setup			= spi_st_setup;
315 	master->cleanup			= spi_st_cleanup;
316 	master->transfer_one		= spi_st_transfer_one;
317 	master->bits_per_word_mask	= SPI_BPW_MASK(8) | SPI_BPW_MASK(16);
318 	master->auto_runtime_pm		= true;
319 	master->bus_num			= pdev->id;
320 	spi_st				= spi_master_get_devdata(master);
321 
322 	spi_st->clk = devm_clk_get(&pdev->dev, "ssc");
323 	if (IS_ERR(spi_st->clk)) {
324 		dev_err(&pdev->dev, "Unable to request clock\n");
325 		ret = PTR_ERR(spi_st->clk);
326 		goto put_master;
327 	}
328 
329 	ret = clk_prepare_enable(spi_st->clk);
330 	if (ret)
331 		goto put_master;
332 
333 	init_completion(&spi_st->done);
334 
335 	/* Get resources */
336 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
337 	spi_st->base = devm_ioremap_resource(&pdev->dev, res);
338 	if (IS_ERR(spi_st->base)) {
339 		ret = PTR_ERR(spi_st->base);
340 		goto clk_disable;
341 	}
342 
343 	/* Disable I2C and Reset SSC */
344 	writel_relaxed(0x0, spi_st->base + SSC_I2C);
345 	var = readw_relaxed(spi_st->base + SSC_CTL);
346 	var |= SSC_CTL_SR;
347 	writel_relaxed(var, spi_st->base + SSC_CTL);
348 
349 	udelay(1);
350 	var = readl_relaxed(spi_st->base + SSC_CTL);
351 	var &= ~SSC_CTL_SR;
352 	writel_relaxed(var, spi_st->base + SSC_CTL);
353 
354 	/* Set SSC into slave mode before reconfiguring PIO pins */
355 	var = readl_relaxed(spi_st->base + SSC_CTL);
356 	var &= ~SSC_CTL_MS;
357 	writel_relaxed(var, spi_st->base + SSC_CTL);
358 
359 	irq = irq_of_parse_and_map(np, 0);
360 	if (!irq) {
361 		dev_err(&pdev->dev, "IRQ missing or invalid\n");
362 		ret = -EINVAL;
363 		goto clk_disable;
364 	}
365 
366 	ret = devm_request_irq(&pdev->dev, irq, spi_st_irq, 0,
367 			       pdev->name, spi_st);
368 	if (ret) {
369 		dev_err(&pdev->dev, "Failed to request irq %d\n", irq);
370 		goto clk_disable;
371 	}
372 
373 	/* by default the device is on */
374 	pm_runtime_set_active(&pdev->dev);
375 	pm_runtime_enable(&pdev->dev);
376 
377 	platform_set_drvdata(pdev, master);
378 
379 	ret = devm_spi_register_master(&pdev->dev, master);
380 	if (ret) {
381 		dev_err(&pdev->dev, "Failed to register master\n");
382 		goto clk_disable;
383 	}
384 
385 	return 0;
386 
387 clk_disable:
388 	clk_disable_unprepare(spi_st->clk);
389 put_master:
390 	spi_master_put(master);
391 	return ret;
392 }
393 
394 static int spi_st_remove(struct platform_device *pdev)
395 {
396 	struct spi_master *master = platform_get_drvdata(pdev);
397 	struct spi_st *spi_st = spi_master_get_devdata(master);
398 
399 	clk_disable_unprepare(spi_st->clk);
400 
401 	pinctrl_pm_select_sleep_state(&pdev->dev);
402 
403 	return 0;
404 }
405 
406 #ifdef CONFIG_PM
407 static int spi_st_runtime_suspend(struct device *dev)
408 {
409 	struct spi_master *master = dev_get_drvdata(dev);
410 	struct spi_st *spi_st = spi_master_get_devdata(master);
411 
412 	writel_relaxed(0, spi_st->base + SSC_IEN);
413 	pinctrl_pm_select_sleep_state(dev);
414 
415 	clk_disable_unprepare(spi_st->clk);
416 
417 	return 0;
418 }
419 
420 static int spi_st_runtime_resume(struct device *dev)
421 {
422 	struct spi_master *master = dev_get_drvdata(dev);
423 	struct spi_st *spi_st = spi_master_get_devdata(master);
424 	int ret;
425 
426 	ret = clk_prepare_enable(spi_st->clk);
427 	pinctrl_pm_select_default_state(dev);
428 
429 	return ret;
430 }
431 #endif
432 
433 #ifdef CONFIG_PM_SLEEP
434 static int spi_st_suspend(struct device *dev)
435 {
436 	struct spi_master *master = dev_get_drvdata(dev);
437 	int ret;
438 
439 	ret = spi_master_suspend(master);
440 	if (ret)
441 		return ret;
442 
443 	return pm_runtime_force_suspend(dev);
444 }
445 
446 static int spi_st_resume(struct device *dev)
447 {
448 	struct spi_master *master = dev_get_drvdata(dev);
449 	int ret;
450 
451 	ret = spi_master_resume(master);
452 	if (ret)
453 		return ret;
454 
455 	return pm_runtime_force_resume(dev);
456 }
457 #endif
458 
459 static const struct dev_pm_ops spi_st_pm = {
460 	SET_SYSTEM_SLEEP_PM_OPS(spi_st_suspend, spi_st_resume)
461 	SET_RUNTIME_PM_OPS(spi_st_runtime_suspend, spi_st_runtime_resume, NULL)
462 };
463 
464 static const struct of_device_id stm_spi_match[] = {
465 	{ .compatible = "st,comms-ssc4-spi", },
466 	{},
467 };
468 MODULE_DEVICE_TABLE(of, stm_spi_match);
469 
470 static struct platform_driver spi_st_driver = {
471 	.driver = {
472 		.name = "spi-st",
473 		.pm = &spi_st_pm,
474 		.of_match_table = of_match_ptr(stm_spi_match),
475 	},
476 	.probe = spi_st_probe,
477 	.remove = spi_st_remove,
478 };
479 module_platform_driver(spi_st_driver);
480 
481 MODULE_AUTHOR("Patrice Chotard <patrice.chotard@st.com>");
482 MODULE_DESCRIPTION("STM SSC SPI driver");
483 MODULE_LICENSE("GPL v2");
484