1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * drivers/pwm/pwm-tegra.c
4 *
5 * Tegra pulse-width-modulation controller driver
6 *
7 * Copyright (c) 2010-2020, NVIDIA Corporation.
8 * Based on arch/arm/plat-mxc/pwm.c by Sascha Hauer <s.hauer@pengutronix.de>
9 *
10 * Overview of Tegra Pulse Width Modulator Register:
11 * 1. 13-bit: Frequency division (SCALE)
12 * 2. 8-bit : Pulse division (DUTY)
13 * 3. 1-bit : Enable bit
14 *
15 * The PWM clock frequency is divided by 256 before subdividing it based
16 * on the programmable frequency division value to generate the required
17 * frequency for PWM output. The maximum output frequency that can be
18 * achieved is (max rate of source clock) / 256.
19 * e.g. if source clock rate is 408 MHz, maximum output frequency can be:
20 * 408 MHz/256 = 1.6 MHz.
21 * This 1.6 MHz frequency can further be divided using SCALE value in PWM.
22 *
23 * PWM pulse width: 8 bits are usable [23:16] for varying pulse width.
24 * To achieve 100% duty cycle, program Bit [24] of this register to
25 * 1’b1. In which case the other bits [23:16] are set to don't care.
26 *
27 * Limitations:
28 * - When PWM is disabled, the output is driven to inactive.
29 * - It does not allow the current PWM period to complete and
30 * stops abruptly.
31 *
32 * - If the register is reconfigured while PWM is running,
33 * it does not complete the currently running period.
34 *
35 * - If the user input duty is beyond acceptible limits,
36 * -EINVAL is returned.
37 */
38
39#include <linux/clk.h>
40#include <linux/err.h>
41#include <linux/io.h>
42#include <linux/module.h>
43#include <linux/of.h>
44#include <linux/pm_opp.h>
45#include <linux/pwm.h>
46#include <linux/platform_device.h>
47#include <linux/pinctrl/consumer.h>
48#include <linux/pm_runtime.h>
49#include <linux/slab.h>
50#include <linux/reset.h>
51
52#include <soc/tegra/common.h>
53
54#define PWM_ENABLE (1 << 31)
55#define PWM_DUTY_WIDTH 8
56#define PWM_DUTY_SHIFT 16
57#define PWM_SCALE_WIDTH 13
58#define PWM_SCALE_SHIFT 0
59
60struct tegra_pwm_soc {
61 unsigned int num_channels;
62
63 /* Maximum IP frequency for given SoCs */
64 unsigned long max_frequency;
65};
66
67struct tegra_pwm_chip {
68 struct clk *clk;
69 struct reset_control*rst;
70
71 unsigned long clk_rate;
72 unsigned long min_period_ns;
73
74 void __iomem *regs;
75
76 const struct tegra_pwm_soc *soc;
77};
78
79static inline struct tegra_pwm_chip *to_tegra_pwm_chip(struct pwm_chip *chip)
80{
81 return pwmchip_get_drvdata(chip);
82}
83
84static inline u32 pwm_readl(struct tegra_pwm_chip *pc, unsigned int offset)
85{
86 return readl(addr: pc->regs + (offset << 4));
87}
88
89static inline void pwm_writel(struct tegra_pwm_chip *pc, unsigned int offset, u32 value)
90{
91 writel(val: value, addr: pc->regs + (offset << 4));
92}
93
94static int tegra_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
95 int duty_ns, int period_ns)
96{
97 struct tegra_pwm_chip *pc = to_tegra_pwm_chip(chip);
98 unsigned long long c = duty_ns;
99 unsigned long rate, required_clk_rate;
100 u32 val = 0;
101 int err;
102
103 /*
104 * Convert from duty_ns / period_ns to a fixed number of duty ticks
105 * per (1 << PWM_DUTY_WIDTH) cycles and make sure to round to the
106 * nearest integer during division.
107 */
108 c *= (1 << PWM_DUTY_WIDTH);
109 c = DIV_ROUND_CLOSEST_ULL(c, period_ns);
110
111 val = (u32)c << PWM_DUTY_SHIFT;
112
113 /*
114 * min period = max clock limit >> PWM_DUTY_WIDTH
115 */
116 if (period_ns < pc->min_period_ns)
117 return -EINVAL;
118
119 /*
120 * Compute the prescaler value for which (1 << PWM_DUTY_WIDTH)
121 * cycles at the PWM clock rate will take period_ns nanoseconds.
122 *
123 * num_channels: If single instance of PWM controller has multiple
124 * channels (e.g. Tegra210 or older) then it is not possible to
125 * configure separate clock rates to each of the channels, in such
126 * case the value stored during probe will be referred.
127 *
128 * If every PWM controller instance has one channel respectively, i.e.
129 * nums_channels == 1 then only the clock rate can be modified
130 * dynamically (e.g. Tegra186 or Tegra194).
131 */
132 if (pc->soc->num_channels == 1) {
133 /*
134 * Rate is multiplied with 2^PWM_DUTY_WIDTH so that it matches
135 * with the maximum possible rate that the controller can
136 * provide. Any further lower value can be derived by setting
137 * PFM bits[0:12].
138 *
139 * required_clk_rate is a reference rate for source clock and
140 * it is derived based on user requested period. By setting the
141 * source clock rate as required_clk_rate, PWM controller will
142 * be able to configure the requested period.
143 */
144 required_clk_rate = DIV_ROUND_UP_ULL((u64)NSEC_PER_SEC << PWM_DUTY_WIDTH,
145 period_ns);
146
147 if (required_clk_rate > clk_round_rate(clk: pc->clk, rate: required_clk_rate))
148 /*
149 * required_clk_rate is a lower bound for the input
150 * rate; for lower rates there is no value for PWM_SCALE
151 * that yields a period less than or equal to the
152 * requested period. Hence, for lower rates, double the
153 * required_clk_rate to get a clock rate that can meet
154 * the requested period.
155 */
156 required_clk_rate *= 2;
157
158 err = dev_pm_opp_set_rate(dev: pwmchip_parent(chip), target_freq: required_clk_rate);
159 if (err < 0)
160 return -EINVAL;
161
162 /* Store the new rate for further references */
163 pc->clk_rate = clk_get_rate(clk: pc->clk);
164 }
165
166 /* Consider precision in PWM_SCALE_WIDTH rate calculation */
167 rate = mul_u64_u64_div_u64(pc->clk_rate, period_ns,
168 (u64)NSEC_PER_SEC << PWM_DUTY_WIDTH);
169
170 /*
171 * Since the actual PWM divider is the register's frequency divider
172 * field plus 1, we need to decrement to get the correct value to
173 * write to the register.
174 */
175 if (rate > 0)
176 rate--;
177 else
178 return -EINVAL;
179
180 /*
181 * Make sure that the rate will fit in the register's frequency
182 * divider field.
183 */
184 if (rate >> PWM_SCALE_WIDTH)
185 return -EINVAL;
186
187 val |= rate << PWM_SCALE_SHIFT;
188
189 /*
190 * If the PWM channel is disabled, make sure to turn on the clock
191 * before writing the register. Otherwise, keep it enabled.
192 */
193 if (!pwm_is_enabled(pwm)) {
194 err = pm_runtime_resume_and_get(dev: pwmchip_parent(chip));
195 if (err)
196 return err;
197 } else
198 val |= PWM_ENABLE;
199
200 pwm_writel(pc, offset: pwm->hwpwm, value: val);
201
202 /*
203 * If the PWM is not enabled, turn the clock off again to save power.
204 */
205 if (!pwm_is_enabled(pwm))
206 pm_runtime_put(dev: pwmchip_parent(chip));
207
208 return 0;
209}
210
211static int tegra_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
212{
213 struct tegra_pwm_chip *pc = to_tegra_pwm_chip(chip);
214 int rc = 0;
215 u32 val;
216
217 rc = pm_runtime_resume_and_get(dev: pwmchip_parent(chip));
218 if (rc)
219 return rc;
220
221 val = pwm_readl(pc, offset: pwm->hwpwm);
222 val |= PWM_ENABLE;
223 pwm_writel(pc, offset: pwm->hwpwm, value: val);
224
225 return 0;
226}
227
228static void tegra_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
229{
230 struct tegra_pwm_chip *pc = to_tegra_pwm_chip(chip);
231 u32 val;
232
233 val = pwm_readl(pc, offset: pwm->hwpwm);
234 val &= ~PWM_ENABLE;
235 pwm_writel(pc, offset: pwm->hwpwm, value: val);
236
237 pm_runtime_put_sync(dev: pwmchip_parent(chip));
238}
239
240static int tegra_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
241 const struct pwm_state *state)
242{
243 int err;
244 bool enabled = pwm->state.enabled;
245
246 if (state->polarity != PWM_POLARITY_NORMAL)
247 return -EINVAL;
248
249 if (!state->enabled) {
250 if (enabled)
251 tegra_pwm_disable(chip, pwm);
252
253 return 0;
254 }
255
256 err = tegra_pwm_config(chip, pwm, duty_ns: state->duty_cycle, period_ns: state->period);
257 if (err)
258 return err;
259
260 if (!enabled)
261 err = tegra_pwm_enable(chip, pwm);
262
263 return err;
264}
265
266static const struct pwm_ops tegra_pwm_ops = {
267 .apply = tegra_pwm_apply,
268};
269
270static int tegra_pwm_probe(struct platform_device *pdev)
271{
272 struct pwm_chip *chip;
273 struct tegra_pwm_chip *pc;
274 const struct tegra_pwm_soc *soc;
275 int ret;
276
277 soc = of_device_get_match_data(dev: &pdev->dev);
278
279 chip = devm_pwmchip_alloc(parent: &pdev->dev, npwm: soc->num_channels, sizeof_priv: sizeof(*pc));
280 if (IS_ERR(ptr: chip))
281 return PTR_ERR(ptr: chip);
282 pc = to_tegra_pwm_chip(chip);
283
284 pc->soc = soc;
285
286 pc->regs = devm_platform_ioremap_resource(pdev, index: 0);
287 if (IS_ERR(ptr: pc->regs))
288 return PTR_ERR(ptr: pc->regs);
289
290 platform_set_drvdata(pdev, data: chip);
291
292 pc->clk = devm_clk_get(dev: &pdev->dev, NULL);
293 if (IS_ERR(ptr: pc->clk))
294 return PTR_ERR(ptr: pc->clk);
295
296 ret = devm_tegra_core_dev_init_opp_table_common(dev: &pdev->dev);
297 if (ret)
298 return ret;
299
300 pm_runtime_enable(dev: &pdev->dev);
301 ret = pm_runtime_resume_and_get(dev: &pdev->dev);
302 if (ret)
303 return ret;
304
305 /* Set maximum frequency of the IP */
306 ret = dev_pm_opp_set_rate(dev: &pdev->dev, target_freq: pc->soc->max_frequency);
307 if (ret < 0) {
308 dev_err(&pdev->dev, "Failed to set max frequency: %d\n", ret);
309 goto put_pm;
310 }
311
312 /*
313 * The requested and configured frequency may differ due to
314 * clock register resolutions. Get the configured frequency
315 * so that PWM period can be calculated more accurately.
316 */
317 pc->clk_rate = clk_get_rate(clk: pc->clk);
318
319 /* Set minimum limit of PWM period for the IP */
320 pc->min_period_ns =
321 (NSEC_PER_SEC / (pc->soc->max_frequency >> PWM_DUTY_WIDTH)) + 1;
322
323 pc->rst = devm_reset_control_get_exclusive(dev: &pdev->dev, id: "pwm");
324 if (IS_ERR(ptr: pc->rst)) {
325 ret = PTR_ERR(ptr: pc->rst);
326 dev_err(&pdev->dev, "Reset control is not found: %d\n", ret);
327 goto put_pm;
328 }
329
330 reset_control_deassert(rstc: pc->rst);
331
332 chip->ops = &tegra_pwm_ops;
333
334 ret = pwmchip_add(chip);
335 if (ret < 0) {
336 dev_err(&pdev->dev, "pwmchip_add() failed: %d\n", ret);
337 reset_control_assert(rstc: pc->rst);
338 goto put_pm;
339 }
340
341 pm_runtime_put(dev: &pdev->dev);
342
343 return 0;
344put_pm:
345 pm_runtime_put_sync_suspend(dev: &pdev->dev);
346 pm_runtime_force_suspend(dev: &pdev->dev);
347 return ret;
348}
349
350static void tegra_pwm_remove(struct platform_device *pdev)
351{
352 struct pwm_chip *chip = platform_get_drvdata(pdev);
353 struct tegra_pwm_chip *pc = to_tegra_pwm_chip(chip);
354
355 pwmchip_remove(chip);
356
357 reset_control_assert(rstc: pc->rst);
358
359 pm_runtime_force_suspend(dev: &pdev->dev);
360}
361
362static int __maybe_unused tegra_pwm_runtime_suspend(struct device *dev)
363{
364 struct pwm_chip *chip = dev_get_drvdata(dev);
365 struct tegra_pwm_chip *pc = to_tegra_pwm_chip(chip);
366 int err;
367
368 clk_disable_unprepare(clk: pc->clk);
369
370 err = pinctrl_pm_select_sleep_state(dev);
371 if (err) {
372 clk_prepare_enable(clk: pc->clk);
373 return err;
374 }
375
376 return 0;
377}
378
379static int __maybe_unused tegra_pwm_runtime_resume(struct device *dev)
380{
381 struct pwm_chip *chip = dev_get_drvdata(dev);
382 struct tegra_pwm_chip *pc = to_tegra_pwm_chip(chip);
383 int err;
384
385 err = pinctrl_pm_select_default_state(dev);
386 if (err)
387 return err;
388
389 err = clk_prepare_enable(clk: pc->clk);
390 if (err) {
391 pinctrl_pm_select_sleep_state(dev);
392 return err;
393 }
394
395 return 0;
396}
397
398static const struct tegra_pwm_soc tegra20_pwm_soc = {
399 .num_channels = 4,
400 .max_frequency = 48000000UL,
401};
402
403static const struct tegra_pwm_soc tegra186_pwm_soc = {
404 .num_channels = 1,
405 .max_frequency = 102000000UL,
406};
407
408static const struct tegra_pwm_soc tegra194_pwm_soc = {
409 .num_channels = 1,
410 .max_frequency = 408000000UL,
411};
412
413static const struct of_device_id tegra_pwm_of_match[] = {
414 { .compatible = "nvidia,tegra20-pwm", .data = &tegra20_pwm_soc },
415 { .compatible = "nvidia,tegra186-pwm", .data = &tegra186_pwm_soc },
416 { .compatible = "nvidia,tegra194-pwm", .data = &tegra194_pwm_soc },
417 { }
418};
419MODULE_DEVICE_TABLE(of, tegra_pwm_of_match);
420
421static const struct dev_pm_ops tegra_pwm_pm_ops = {
422 SET_RUNTIME_PM_OPS(tegra_pwm_runtime_suspend, tegra_pwm_runtime_resume,
423 NULL)
424 SET_SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend,
425 pm_runtime_force_resume)
426};
427
428static struct platform_driver tegra_pwm_driver = {
429 .driver = {
430 .name = "tegra-pwm",
431 .of_match_table = tegra_pwm_of_match,
432 .pm = &tegra_pwm_pm_ops,
433 },
434 .probe = tegra_pwm_probe,
435 .remove = tegra_pwm_remove,
436};
437
438module_platform_driver(tegra_pwm_driver);
439
440MODULE_LICENSE("GPL");
441MODULE_AUTHOR("Sandipan Patra <spatra@nvidia.com>");
442MODULE_DESCRIPTION("Tegra PWM controller driver");
443MODULE_ALIAS("platform:tegra-pwm");
444

source code of linux/drivers/pwm/pwm-tegra.c