1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * Copyright (c) 2015 Neil Armstrong <narmstrong@baylibre.com>
4  * Copyright (c) 2014 Joachim Eastwood <manabian@gmail.com>
5  * Copyright (c) 2012 NeilBrown <neilb@suse.de>
6  * Heavily based on earlier code which is:
7  * Copyright (c) 2010 Grant Erickson <marathon96@gmail.com>
8  *
9  * Also based on pwm-samsung.c
10  *
11  * Description:
12  *   This file is the core OMAP support for the generic, Linux
13  *   PWM driver / controller, using the OMAP's dual-mode timers
14  *   with a timer counter that goes up. When it overflows it gets
15  *   reloaded with the load value and the pwm output goes up.
16  *   When counter matches with match register, the output goes down.
17  *   Reference Manual: https://www.ti.com/lit/ug/spruh73q/spruh73q.pdf
18  *
19  * Limitations:
20  * - When PWM is stopped, timer counter gets stopped immediately. This
21  *   doesn't allow the current PWM period to complete and stops abruptly.
22  * - When PWM is running and changing both duty cycle and period,
23  *   we cannot prevent in software that the output might produce
24  *   a period with mixed settings. Especially when period/duty_cyle
25  *   is updated while the pwm pin is high, current pwm period/duty_cycle
26  *   can get updated as below based on the current timer counter:
27  *   	- period for current cycle =  current_period + new period
28  *   	- duty_cycle for current period = current period + new duty_cycle.
29  * - PWM OMAP DM timer cannot change the polarity when pwm is active. When
30  *   user requests a change in polarity when in active state:
31  *	- PWM is stopped abruptly(without completing the current cycle)
32  *	- Polarity is changed
33  *	- A fresh cycle is started.
34  */
35 
36 #include <linux/clk.h>
37 #include <linux/err.h>
38 #include <linux/kernel.h>
39 #include <linux/module.h>
40 #include <linux/mutex.h>
41 #include <linux/of.h>
42 #include <linux/of_platform.h>
43 #include <clocksource/timer-ti-dm.h>
44 #include <linux/platform_data/dmtimer-omap.h>
45 #include <linux/platform_device.h>
46 #include <linux/pm_runtime.h>
47 #include <linux/pwm.h>
48 #include <linux/slab.h>
49 #include <linux/time.h>
50 
51 #define DM_TIMER_LOAD_MIN 0xfffffffe
52 #define DM_TIMER_MAX      0xffffffff
53 
54 /**
55  * struct pwm_omap_dmtimer_chip - Structure representing a pwm chip
56  *				  corresponding to omap dmtimer.
57  * @chip:		PWM chip structure representing PWM controller
58  * @mutex:		Mutex to protect pwm apply state
59  * @dm_timer:		Pointer to omap dm timer.
60  * @pdata:		Pointer to omap dm timer ops.
61  * @dm_timer_pdev:	Pointer to omap dm timer platform device
62  */
63 struct pwm_omap_dmtimer_chip {
64 	struct pwm_chip chip;
65 	/* Mutex to protect pwm apply state */
66 	struct mutex mutex;
67 	struct omap_dm_timer *dm_timer;
68 	const struct omap_dm_timer_ops *pdata;
69 	struct platform_device *dm_timer_pdev;
70 };
71 
72 static inline struct pwm_omap_dmtimer_chip *
to_pwm_omap_dmtimer_chip(struct pwm_chip * chip)73 to_pwm_omap_dmtimer_chip(struct pwm_chip *chip)
74 {
75 	return container_of(chip, struct pwm_omap_dmtimer_chip, chip);
76 }
77 
78 /**
79  * pwm_omap_dmtimer_get_clock_cycles() - Get clock cycles in a time frame
80  * @clk_rate:	pwm timer clock rate
81  * @ns:		time frame in nano seconds.
82  *
83  * Return number of clock cycles in a given period(ins ns).
84  */
pwm_omap_dmtimer_get_clock_cycles(unsigned long clk_rate,int ns)85 static u32 pwm_omap_dmtimer_get_clock_cycles(unsigned long clk_rate, int ns)
86 {
87 	return DIV_ROUND_CLOSEST_ULL((u64)clk_rate * ns, NSEC_PER_SEC);
88 }
89 
90 /**
91  * pwm_omap_dmtimer_start() - Start the pwm omap dm timer in pwm mode
92  * @omap:	Pointer to pwm omap dm timer chip
93  */
pwm_omap_dmtimer_start(struct pwm_omap_dmtimer_chip * omap)94 static void pwm_omap_dmtimer_start(struct pwm_omap_dmtimer_chip *omap)
95 {
96 	/*
97 	 * According to OMAP 4 TRM section 22.2.4.10 the counter should be
98 	 * started at 0xFFFFFFFE when overflow and match is used to ensure
99 	 * that the PWM line is toggled on the first event.
100 	 *
101 	 * Note that omap_dm_timer_enable/disable is for register access and
102 	 * not the timer counter itself.
103 	 */
104 	omap->pdata->enable(omap->dm_timer);
105 	omap->pdata->write_counter(omap->dm_timer, DM_TIMER_LOAD_MIN);
106 	omap->pdata->disable(omap->dm_timer);
107 
108 	omap->pdata->start(omap->dm_timer);
109 }
110 
111 /**
112  * pwm_omap_dmtimer_is_enabled() -  Detect if the pwm is enabled.
113  * @omap:	Pointer to pwm omap dm timer chip
114  *
115  * Return true if pwm is enabled else false.
116  */
pwm_omap_dmtimer_is_enabled(struct pwm_omap_dmtimer_chip * omap)117 static bool pwm_omap_dmtimer_is_enabled(struct pwm_omap_dmtimer_chip *omap)
118 {
119 	u32 status;
120 
121 	status = omap->pdata->get_pwm_status(omap->dm_timer);
122 
123 	return !!(status & OMAP_TIMER_CTRL_ST);
124 }
125 
126 /**
127  * pwm_omap_dmtimer_polarity() -  Detect the polarity of pwm.
128  * @omap:	Pointer to pwm omap dm timer chip
129  *
130  * Return the polarity of pwm.
131  */
pwm_omap_dmtimer_polarity(struct pwm_omap_dmtimer_chip * omap)132 static int pwm_omap_dmtimer_polarity(struct pwm_omap_dmtimer_chip *omap)
133 {
134 	u32 status;
135 
136 	status = omap->pdata->get_pwm_status(omap->dm_timer);
137 
138 	return !!(status & OMAP_TIMER_CTRL_SCPWM);
139 }
140 
141 /**
142  * pwm_omap_dmtimer_config() - Update the configuration of pwm omap dm timer
143  * @chip:	Pointer to PWM controller
144  * @pwm:	Pointer to PWM channel
145  * @duty_ns:	New duty cycle in nano seconds
146  * @period_ns:	New period in nano seconds
147  *
148  * Return 0 if successfully changed the period/duty_cycle else appropriate
149  * error.
150  */
pwm_omap_dmtimer_config(struct pwm_chip * chip,struct pwm_device * pwm,int duty_ns,int period_ns)151 static int pwm_omap_dmtimer_config(struct pwm_chip *chip,
152 				   struct pwm_device *pwm,
153 				   int duty_ns, int period_ns)
154 {
155 	struct pwm_omap_dmtimer_chip *omap = to_pwm_omap_dmtimer_chip(chip);
156 	u32 period_cycles, duty_cycles;
157 	u32 load_value, match_value;
158 	unsigned long clk_rate;
159 	struct clk *fclk;
160 
161 	dev_dbg(chip->dev, "requested duty cycle: %d ns, period: %d ns\n",
162 		duty_ns, period_ns);
163 
164 	if (duty_ns == pwm_get_duty_cycle(pwm) &&
165 	    period_ns == pwm_get_period(pwm))
166 		return 0;
167 
168 	fclk = omap->pdata->get_fclk(omap->dm_timer);
169 	if (!fclk) {
170 		dev_err(chip->dev, "invalid pmtimer fclk\n");
171 		return -EINVAL;
172 	}
173 
174 	clk_rate = clk_get_rate(fclk);
175 	if (!clk_rate) {
176 		dev_err(chip->dev, "invalid pmtimer fclk rate\n");
177 		return -EINVAL;
178 	}
179 
180 	dev_dbg(chip->dev, "clk rate: %luHz\n", clk_rate);
181 
182 	/*
183 	 * Calculate the appropriate load and match values based on the
184 	 * specified period and duty cycle. The load value determines the
185 	 * period time and the match value determines the duty time.
186 	 *
187 	 * The period lasts for (DM_TIMER_MAX-load_value+1) clock cycles.
188 	 * Similarly, the active time lasts (match_value-load_value+1) cycles.
189 	 * The non-active time is the remainder: (DM_TIMER_MAX-match_value)
190 	 * clock cycles.
191 	 *
192 	 * NOTE: It is required that: load_value <= match_value < DM_TIMER_MAX
193 	 *
194 	 * References:
195 	 *   OMAP4430/60/70 TRM sections 22.2.4.10 and 22.2.4.11
196 	 *   AM335x Sitara TRM sections 20.1.3.5 and 20.1.3.6
197 	 */
198 	period_cycles = pwm_omap_dmtimer_get_clock_cycles(clk_rate, period_ns);
199 	duty_cycles = pwm_omap_dmtimer_get_clock_cycles(clk_rate, duty_ns);
200 
201 	if (period_cycles < 2) {
202 		dev_info(chip->dev,
203 			 "period %d ns too short for clock rate %lu Hz\n",
204 			 period_ns, clk_rate);
205 		return -EINVAL;
206 	}
207 
208 	if (duty_cycles < 1) {
209 		dev_dbg(chip->dev,
210 			"duty cycle %d ns is too short for clock rate %lu Hz\n",
211 			duty_ns, clk_rate);
212 		dev_dbg(chip->dev, "using minimum of 1 clock cycle\n");
213 		duty_cycles = 1;
214 	} else if (duty_cycles >= period_cycles) {
215 		dev_dbg(chip->dev,
216 			"duty cycle %d ns is too long for period %d ns at clock rate %lu Hz\n",
217 			duty_ns, period_ns, clk_rate);
218 		dev_dbg(chip->dev, "using maximum of 1 clock cycle less than period\n");
219 		duty_cycles = period_cycles - 1;
220 	}
221 
222 	dev_dbg(chip->dev, "effective duty cycle: %lld ns, period: %lld ns\n",
223 		DIV_ROUND_CLOSEST_ULL((u64)NSEC_PER_SEC * duty_cycles,
224 				      clk_rate),
225 		DIV_ROUND_CLOSEST_ULL((u64)NSEC_PER_SEC * period_cycles,
226 				      clk_rate));
227 
228 	load_value = (DM_TIMER_MAX - period_cycles) + 1;
229 	match_value = load_value + duty_cycles - 1;
230 
231 	omap->pdata->set_load(omap->dm_timer, load_value);
232 	omap->pdata->set_match(omap->dm_timer, true, match_value);
233 
234 	dev_dbg(chip->dev, "load value: %#08x (%d), match value: %#08x (%d)\n",
235 		load_value, load_value,	match_value, match_value);
236 
237 	return 0;
238 }
239 
240 /**
241  * pwm_omap_dmtimer_set_polarity() - Changes the polarity of the pwm dm timer.
242  * @chip:	Pointer to PWM controller
243  * @pwm:	Pointer to PWM channel
244  * @polarity:	New pwm polarity to be set
245  */
pwm_omap_dmtimer_set_polarity(struct pwm_chip * chip,struct pwm_device * pwm,enum pwm_polarity polarity)246 static void pwm_omap_dmtimer_set_polarity(struct pwm_chip *chip,
247 					  struct pwm_device *pwm,
248 					  enum pwm_polarity polarity)
249 {
250 	struct pwm_omap_dmtimer_chip *omap = to_pwm_omap_dmtimer_chip(chip);
251 	bool enabled;
252 
253 	/* Disable the PWM before changing the polarity. */
254 	enabled = pwm_omap_dmtimer_is_enabled(omap);
255 	if (enabled)
256 		omap->pdata->stop(omap->dm_timer);
257 
258 	omap->pdata->set_pwm(omap->dm_timer,
259 			     polarity == PWM_POLARITY_INVERSED,
260 			     true, OMAP_TIMER_TRIGGER_OVERFLOW_AND_COMPARE,
261 			     true);
262 
263 	if (enabled)
264 		pwm_omap_dmtimer_start(omap);
265 }
266 
267 /**
268  * pwm_omap_dmtimer_apply() - Changes the state of the pwm omap dm timer.
269  * @chip:	Pointer to PWM controller
270  * @pwm:	Pointer to PWM channel
271  * @state:	New state to apply
272  *
273  * Return 0 if successfully changed the state else appropriate error.
274  */
pwm_omap_dmtimer_apply(struct pwm_chip * chip,struct pwm_device * pwm,const struct pwm_state * state)275 static int pwm_omap_dmtimer_apply(struct pwm_chip *chip,
276 				  struct pwm_device *pwm,
277 				  const struct pwm_state *state)
278 {
279 	struct pwm_omap_dmtimer_chip *omap = to_pwm_omap_dmtimer_chip(chip);
280 	int ret = 0;
281 
282 	mutex_lock(&omap->mutex);
283 
284 	if (pwm_omap_dmtimer_is_enabled(omap) && !state->enabled) {
285 		omap->pdata->stop(omap->dm_timer);
286 		goto unlock_mutex;
287 	}
288 
289 	if (pwm_omap_dmtimer_polarity(omap) != state->polarity)
290 		pwm_omap_dmtimer_set_polarity(chip, pwm, state->polarity);
291 
292 	ret = pwm_omap_dmtimer_config(chip, pwm, state->duty_cycle,
293 				      state->period);
294 	if (ret)
295 		goto unlock_mutex;
296 
297 	if (!pwm_omap_dmtimer_is_enabled(omap) && state->enabled) {
298 		omap->pdata->set_pwm(omap->dm_timer,
299 				     state->polarity == PWM_POLARITY_INVERSED,
300 				     true,
301 				     OMAP_TIMER_TRIGGER_OVERFLOW_AND_COMPARE,
302 				     true);
303 		pwm_omap_dmtimer_start(omap);
304 	}
305 
306 unlock_mutex:
307 	mutex_unlock(&omap->mutex);
308 
309 	return ret;
310 }
311 
312 static const struct pwm_ops pwm_omap_dmtimer_ops = {
313 	.apply = pwm_omap_dmtimer_apply,
314 	.owner = THIS_MODULE,
315 };
316 
pwm_omap_dmtimer_probe(struct platform_device * pdev)317 static int pwm_omap_dmtimer_probe(struct platform_device *pdev)
318 {
319 	struct device_node *np = pdev->dev.of_node;
320 	struct dmtimer_platform_data *timer_pdata;
321 	const struct omap_dm_timer_ops *pdata;
322 	struct platform_device *timer_pdev;
323 	struct pwm_omap_dmtimer_chip *omap;
324 	struct omap_dm_timer *dm_timer;
325 	struct device_node *timer;
326 	int ret = 0;
327 	u32 v;
328 
329 	timer = of_parse_phandle(np, "ti,timers", 0);
330 	if (!timer)
331 		return -ENODEV;
332 
333 	timer_pdev = of_find_device_by_node(timer);
334 	if (!timer_pdev) {
335 		dev_err(&pdev->dev, "Unable to find Timer pdev\n");
336 		ret = -ENODEV;
337 		goto err_find_timer_pdev;
338 	}
339 
340 	timer_pdata = dev_get_platdata(&timer_pdev->dev);
341 	if (!timer_pdata) {
342 		dev_dbg(&pdev->dev,
343 			 "dmtimer pdata structure NULL, deferring probe\n");
344 		ret = -EPROBE_DEFER;
345 		goto err_platdata;
346 	}
347 
348 	pdata = timer_pdata->timer_ops;
349 
350 	if (!pdata || !pdata->request_by_node ||
351 	    !pdata->free ||
352 	    !pdata->enable ||
353 	    !pdata->disable ||
354 	    !pdata->get_fclk ||
355 	    !pdata->start ||
356 	    !pdata->stop ||
357 	    !pdata->set_load ||
358 	    !pdata->set_match ||
359 	    !pdata->set_pwm ||
360 	    !pdata->get_pwm_status ||
361 	    !pdata->set_prescaler ||
362 	    !pdata->write_counter) {
363 		dev_err(&pdev->dev, "Incomplete dmtimer pdata structure\n");
364 		ret = -EINVAL;
365 		goto err_platdata;
366 	}
367 
368 	if (!of_get_property(timer, "ti,timer-pwm", NULL)) {
369 		dev_err(&pdev->dev, "Missing ti,timer-pwm capability\n");
370 		ret = -ENODEV;
371 		goto err_timer_property;
372 	}
373 
374 	dm_timer = pdata->request_by_node(timer);
375 	if (!dm_timer) {
376 		ret = -EPROBE_DEFER;
377 		goto err_request_timer;
378 	}
379 
380 	omap = devm_kzalloc(&pdev->dev, sizeof(*omap), GFP_KERNEL);
381 	if (!omap) {
382 		ret = -ENOMEM;
383 		goto err_alloc_omap;
384 	}
385 
386 	omap->pdata = pdata;
387 	omap->dm_timer = dm_timer;
388 	omap->dm_timer_pdev = timer_pdev;
389 
390 	/*
391 	 * Ensure that the timer is stopped before we allow PWM core to call
392 	 * pwm_enable.
393 	 */
394 	if (pm_runtime_active(&omap->dm_timer_pdev->dev))
395 		omap->pdata->stop(omap->dm_timer);
396 
397 	if (!of_property_read_u32(pdev->dev.of_node, "ti,prescaler", &v))
398 		omap->pdata->set_prescaler(omap->dm_timer, v);
399 
400 	/* setup dmtimer clock source */
401 	if (!of_property_read_u32(pdev->dev.of_node, "ti,clock-source", &v))
402 		omap->pdata->set_source(omap->dm_timer, v);
403 
404 	omap->chip.dev = &pdev->dev;
405 	omap->chip.ops = &pwm_omap_dmtimer_ops;
406 	omap->chip.npwm = 1;
407 
408 	mutex_init(&omap->mutex);
409 
410 	ret = pwmchip_add(&omap->chip);
411 	if (ret < 0) {
412 		dev_err(&pdev->dev, "failed to register PWM\n");
413 		goto err_pwmchip_add;
414 	}
415 
416 	of_node_put(timer);
417 
418 	platform_set_drvdata(pdev, omap);
419 
420 	return 0;
421 
422 err_pwmchip_add:
423 
424 	/*
425 	 * *omap is allocated using devm_kzalloc,
426 	 * so no free necessary here
427 	 */
428 err_alloc_omap:
429 
430 	pdata->free(dm_timer);
431 err_request_timer:
432 
433 err_timer_property:
434 err_platdata:
435 
436 	put_device(&timer_pdev->dev);
437 err_find_timer_pdev:
438 
439 	of_node_put(timer);
440 
441 	return ret;
442 }
443 
pwm_omap_dmtimer_remove(struct platform_device * pdev)444 static void pwm_omap_dmtimer_remove(struct platform_device *pdev)
445 {
446 	struct pwm_omap_dmtimer_chip *omap = platform_get_drvdata(pdev);
447 
448 	pwmchip_remove(&omap->chip);
449 
450 	if (pm_runtime_active(&omap->dm_timer_pdev->dev))
451 		omap->pdata->stop(omap->dm_timer);
452 
453 	omap->pdata->free(omap->dm_timer);
454 
455 	put_device(&omap->dm_timer_pdev->dev);
456 
457 	mutex_destroy(&omap->mutex);
458 }
459 
460 static const struct of_device_id pwm_omap_dmtimer_of_match[] = {
461 	{.compatible = "ti,omap-dmtimer-pwm"},
462 	{}
463 };
464 MODULE_DEVICE_TABLE(of, pwm_omap_dmtimer_of_match);
465 
466 static struct platform_driver pwm_omap_dmtimer_driver = {
467 	.driver = {
468 		.name = "omap-dmtimer-pwm",
469 		.of_match_table = of_match_ptr(pwm_omap_dmtimer_of_match),
470 	},
471 	.probe = pwm_omap_dmtimer_probe,
472 	.remove_new = pwm_omap_dmtimer_remove,
473 };
474 module_platform_driver(pwm_omap_dmtimer_driver);
475 
476 MODULE_AUTHOR("Grant Erickson <marathon96@gmail.com>");
477 MODULE_AUTHOR("NeilBrown <neilb@suse.de>");
478 MODULE_AUTHOR("Neil Armstrong <narmstrong@baylibre.com>");
479 MODULE_LICENSE("GPL v2");
480 MODULE_DESCRIPTION("OMAP PWM Driver using Dual-mode Timers");
481