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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/of_device.h>
45#include <linux/pwm.h>
46#include <linux/platform_device.h>
47#include <linux/pinctrl/consumer.h>
48#include <linux/slab.h>
49#include <linux/reset.h>
50
51#define PWM_ENABLE (1 << 31)
52#define PWM_DUTY_WIDTH 8
53#define PWM_DUTY_SHIFT 16
54#define PWM_SCALE_WIDTH 13
55#define PWM_SCALE_SHIFT 0
56
57struct tegra_pwm_soc {
58 unsigned int num_channels;
59
60 /* Maximum IP frequency for given SoCs */
61 unsigned long max_frequency;
62};
63
64struct tegra_pwm_chip {
65 struct pwm_chip chip;
66 struct device *dev;
67
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 container_of(chip, struct tegra_pwm_chip, chip);
82}
83
84static inline u32 pwm_readl(struct tegra_pwm_chip *chip, unsigned int num)
85{
86 return readl(chip->regs + (num << 4));
87}
88
89static inline void pwm_writel(struct tegra_pwm_chip *chip, unsigned int num,
90 unsigned long val)
91{
92 writel(val, chip->regs + (num << 4));
93}
94
95static int tegra_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
96 int duty_ns, int period_ns)
97{
98 struct tegra_pwm_chip *pc = to_tegra_pwm_chip(chip);
99 unsigned long long c = duty_ns, hz;
100 unsigned long rate, required_clk_rate;
101 u32 val = 0;
102 int err;
103
104 /*
105 * Convert from duty_ns / period_ns to a fixed number of duty ticks
106 * per (1 << PWM_DUTY_WIDTH) cycles and make sure to round to the
107 * nearest integer during division.
108 */
109 c *= (1 << PWM_DUTY_WIDTH);
110 c = DIV_ROUND_CLOSEST_ULL(c, period_ns);
111
112 val = (u32)c << PWM_DUTY_SHIFT;
113
114 /*
115 * min period = max clock limit >> PWM_DUTY_WIDTH
116 */
117 if (period_ns < pc->min_period_ns)
118 return -EINVAL;
119
120 /*
121 * Compute the prescaler value for which (1 << PWM_DUTY_WIDTH)
122 * cycles at the PWM clock rate will take period_ns nanoseconds.
123 *
124 * num_channels: If single instance of PWM controller has multiple
125 * channels (e.g. Tegra210 or older) then it is not possible to
126 * configure separate clock rates to each of the channels, in such
127 * case the value stored during probe will be referred.
128 *
129 * If every PWM controller instance has one channel respectively, i.e.
130 * nums_channels == 1 then only the clock rate can be modified
131 * dynamically (e.g. Tegra186 or Tegra194).
132 */
133 if (pc->soc->num_channels == 1) {
134 /*
135 * Rate is multiplied with 2^PWM_DUTY_WIDTH so that it matches
136 * with the maximum possible rate that the controller can
137 * provide. Any further lower value can be derived by setting
138 * PFM bits[0:12].
139 *
140 * required_clk_rate is a reference rate for source clock and
141 * it is derived based on user requested period. By setting the
142 * source clock rate as required_clk_rate, PWM controller will
143 * be able to configure the requested period.
144 */
145 required_clk_rate =
146 (NSEC_PER_SEC / period_ns) << PWM_DUTY_WIDTH;
147
148 err = clk_set_rate(pc->clk, required_clk_rate);
149 if (err < 0)
150 return -EINVAL;
151
152 /* Store the new rate for further references */
153 pc->clk_rate = clk_get_rate(pc->clk);
154 }
155
156 rate = pc->clk_rate >> PWM_DUTY_WIDTH;
157
158 /* Consider precision in PWM_SCALE_WIDTH rate calculation */
159 hz = DIV_ROUND_CLOSEST_ULL(100ULL * NSEC_PER_SEC, period_ns);
160 rate = DIV_ROUND_CLOSEST_ULL(100ULL * rate, hz);
161
162 /*
163 * Since the actual PWM divider is the register's frequency divider
164 * field plus 1, we need to decrement to get the correct value to
165 * write to the register.
166 */
167 if (rate > 0)
168 rate--;
169
170 /*
171 * Make sure that the rate will fit in the register's frequency
172 * divider field.
173 */
174 if (rate >> PWM_SCALE_WIDTH)
175 return -EINVAL;
176
177 val |= rate << PWM_SCALE_SHIFT;
178
179 /*
180 * If the PWM channel is disabled, make sure to turn on the clock
181 * before writing the register. Otherwise, keep it enabled.
182 */
183 if (!pwm_is_enabled(pwm)) {
184 err = clk_prepare_enable(pc->clk);
185 if (err < 0)
186 return err;
187 } else
188 val |= PWM_ENABLE;
189
190 pwm_writel(pc, pwm->hwpwm, val);
191
192 /*
193 * If the PWM is not enabled, turn the clock off again to save power.
194 */
195 if (!pwm_is_enabled(pwm))
196 clk_disable_unprepare(pc->clk);
197
198 return 0;
199}
200
201static int tegra_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
202{
203 struct tegra_pwm_chip *pc = to_tegra_pwm_chip(chip);
204 int rc = 0;
205 u32 val;
206
207 rc = clk_prepare_enable(pc->clk);
208 if (rc < 0)
209 return rc;
210
211 val = pwm_readl(pc, pwm->hwpwm);
212 val |= PWM_ENABLE;
213 pwm_writel(pc, pwm->hwpwm, val);
214
215 return 0;
216}
217
218static void tegra_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
219{
220 struct tegra_pwm_chip *pc = to_tegra_pwm_chip(chip);
221 u32 val;
222
223 val = pwm_readl(pc, pwm->hwpwm);
224 val &= ~PWM_ENABLE;
225 pwm_writel(pc, pwm->hwpwm, val);
226
227 clk_disable_unprepare(pc->clk);
228}
229
230static const struct pwm_ops tegra_pwm_ops = {
231 .config = tegra_pwm_config,
232 .enable = tegra_pwm_enable,
233 .disable = tegra_pwm_disable,
234 .owner = THIS_MODULE,
235};
236
237static int tegra_pwm_probe(struct platform_device *pdev)
238{
239 struct tegra_pwm_chip *pwm;
240 struct resource *r;
241 int ret;
242
243 pwm = devm_kzalloc(&pdev->dev, sizeof(*pwm), GFP_KERNEL);
244 if (!pwm)
245 return -ENOMEM;
246
247 pwm->soc = of_device_get_match_data(&pdev->dev);
248 pwm->dev = &pdev->dev;
249
250 r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
251 pwm->regs = devm_ioremap_resource(&pdev->dev, r);
252 if (IS_ERR(pwm->regs))
253 return PTR_ERR(pwm->regs);
254
255 platform_set_drvdata(pdev, pwm);
256
257 pwm->clk = devm_clk_get(&pdev->dev, NULL);
258 if (IS_ERR(pwm->clk))
259 return PTR_ERR(pwm->clk);
260
261 /* Set maximum frequency of the IP */
262 ret = clk_set_rate(pwm->clk, pwm->soc->max_frequency);
263 if (ret < 0) {
264 dev_err(&pdev->dev, "Failed to set max frequency: %d\n", ret);
265 return ret;
266 }
267
268 /*
269 * The requested and configured frequency may differ due to
270 * clock register resolutions. Get the configured frequency
271 * so that PWM period can be calculated more accurately.
272 */
273 pwm->clk_rate = clk_get_rate(pwm->clk);
274
275 /* Set minimum limit of PWM period for the IP */
276 pwm->min_period_ns =
277 (NSEC_PER_SEC / (pwm->soc->max_frequency >> PWM_DUTY_WIDTH)) + 1;
278
279 pwm->rst = devm_reset_control_get_exclusive(&pdev->dev, "pwm");
280 if (IS_ERR(pwm->rst)) {
281 ret = PTR_ERR(pwm->rst);
282 dev_err(&pdev->dev, "Reset control is not found: %d\n", ret);
283 return ret;
284 }
285
286 reset_control_deassert(pwm->rst);
287
288 pwm->chip.dev = &pdev->dev;
289 pwm->chip.ops = &tegra_pwm_ops;
290 pwm->chip.base = -1;
291 pwm->chip.npwm = pwm->soc->num_channels;
292
293 ret = pwmchip_add(&pwm->chip);
294 if (ret < 0) {
295 dev_err(&pdev->dev, "pwmchip_add() failed: %d\n", ret);
296 reset_control_assert(pwm->rst);
297 return ret;
298 }
299
300 return 0;
301}
302
303static int tegra_pwm_remove(struct platform_device *pdev)
304{
305 struct tegra_pwm_chip *pc = platform_get_drvdata(pdev);
306 unsigned int i;
307 int err;
308
309 if (WARN_ON(!pc))
310 return -ENODEV;
311
312 err = clk_prepare_enable(pc->clk);
313 if (err < 0)
314 return err;
315
316 for (i = 0; i < pc->chip.npwm; i++) {
317 struct pwm_device *pwm = &pc->chip.pwms[i];
318
319 if (!pwm_is_enabled(pwm))
320 if (clk_prepare_enable(pc->clk) < 0)
321 continue;
322
323 pwm_writel(pc, i, 0);
324
325 clk_disable_unprepare(pc->clk);
326 }
327
328 reset_control_assert(pc->rst);
329 clk_disable_unprepare(pc->clk);
330
331 return pwmchip_remove(&pc->chip);
332}
333
334#ifdef CONFIG_PM_SLEEP
335static int tegra_pwm_suspend(struct device *dev)
336{
337 return pinctrl_pm_select_sleep_state(dev);
338}
339
340static int tegra_pwm_resume(struct device *dev)
341{
342 return pinctrl_pm_select_default_state(dev);
343}
344#endif
345
346static const struct tegra_pwm_soc tegra20_pwm_soc = {
347 .num_channels = 4,
348 .max_frequency = 48000000UL,
349};
350
351static const struct tegra_pwm_soc tegra186_pwm_soc = {
352 .num_channels = 1,
353 .max_frequency = 102000000UL,
354};
355
356static const struct tegra_pwm_soc tegra194_pwm_soc = {
357 .num_channels = 1,
358 .max_frequency = 408000000UL,
359};
360
361static const struct of_device_id tegra_pwm_of_match[] = {
362 { .compatible = "nvidia,tegra20-pwm", .data = &tegra20_pwm_soc },
363 { .compatible = "nvidia,tegra186-pwm", .data = &tegra186_pwm_soc },
364 { .compatible = "nvidia,tegra194-pwm", .data = &tegra194_pwm_soc },
365 { }
366};
367MODULE_DEVICE_TABLE(of, tegra_pwm_of_match);
368
369static const struct dev_pm_ops tegra_pwm_pm_ops = {
370 SET_SYSTEM_SLEEP_PM_OPS(tegra_pwm_suspend, tegra_pwm_resume)
371};
372
373static struct platform_driver tegra_pwm_driver = {
374 .driver = {
375 .name = "tegra-pwm",
376 .of_match_table = tegra_pwm_of_match,
377 .pm = &tegra_pwm_pm_ops,
378 },
379 .probe = tegra_pwm_probe,
380 .remove = tegra_pwm_remove,
381};
382
383module_platform_driver(tegra_pwm_driver);
384
385MODULE_LICENSE("GPL");
386MODULE_AUTHOR("Sandipan Patra <spatra@nvidia.com>");
387MODULE_DESCRIPTION("Tegra PWM controller driver");
388MODULE_ALIAS("platform:tegra-pwm");
1/*
2 * drivers/pwm/pwm-tegra.c
3 *
4 * Tegra pulse-width-modulation controller driver
5 *
6 * Copyright (c) 2010, NVIDIA Corporation.
7 * Based on arch/arm/plat-mxc/pwm.c by Sascha Hauer <s.hauer@pengutronix.de>
8 *
9 * This program is free software; you can redistribute it and/or modify
10 * it under the terms of the GNU General Public License as published by
11 * the Free Software Foundation; either version 2 of the License, or
12 * (at your option) any later version.
13 *
14 * This program is distributed in the hope that it will be useful, but WITHOUT
15 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
16 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
17 * more details.
18 *
19 * You should have received a copy of the GNU General Public License along
20 * with this program; if not, write to the Free Software Foundation, Inc.,
21 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
22 */
23
24#include <linux/clk.h>
25#include <linux/err.h>
26#include <linux/io.h>
27#include <linux/module.h>
28#include <linux/of.h>
29#include <linux/of_device.h>
30#include <linux/pwm.h>
31#include <linux/platform_device.h>
32#include <linux/pinctrl/consumer.h>
33#include <linux/slab.h>
34#include <linux/reset.h>
35
36#define PWM_ENABLE (1 << 31)
37#define PWM_DUTY_WIDTH 8
38#define PWM_DUTY_SHIFT 16
39#define PWM_SCALE_WIDTH 13
40#define PWM_SCALE_SHIFT 0
41
42struct tegra_pwm_soc {
43 unsigned int num_channels;
44
45 /* Maximum IP frequency for given SoCs */
46 unsigned long max_frequency;
47};
48
49struct tegra_pwm_chip {
50 struct pwm_chip chip;
51 struct device *dev;
52
53 struct clk *clk;
54 struct reset_control*rst;
55
56 unsigned long clk_rate;
57
58 void __iomem *regs;
59
60 const struct tegra_pwm_soc *soc;
61};
62
63static inline struct tegra_pwm_chip *to_tegra_pwm_chip(struct pwm_chip *chip)
64{
65 return container_of(chip, struct tegra_pwm_chip, chip);
66}
67
68static inline u32 pwm_readl(struct tegra_pwm_chip *chip, unsigned int num)
69{
70 return readl(chip->regs + (num << 4));
71}
72
73static inline void pwm_writel(struct tegra_pwm_chip *chip, unsigned int num,
74 unsigned long val)
75{
76 writel(val, chip->regs + (num << 4));
77}
78
79static int tegra_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
80 int duty_ns, int period_ns)
81{
82 struct tegra_pwm_chip *pc = to_tegra_pwm_chip(chip);
83 unsigned long long c = duty_ns, hz;
84 unsigned long rate;
85 u32 val = 0;
86 int err;
87
88 /*
89 * Convert from duty_ns / period_ns to a fixed number of duty ticks
90 * per (1 << PWM_DUTY_WIDTH) cycles and make sure to round to the
91 * nearest integer during division.
92 */
93 c *= (1 << PWM_DUTY_WIDTH);
94 c = DIV_ROUND_CLOSEST_ULL(c, period_ns);
95
96 val = (u32)c << PWM_DUTY_SHIFT;
97
98 /*
99 * Compute the prescaler value for which (1 << PWM_DUTY_WIDTH)
100 * cycles at the PWM clock rate will take period_ns nanoseconds.
101 */
102 rate = pc->clk_rate >> PWM_DUTY_WIDTH;
103
104 /* Consider precision in PWM_SCALE_WIDTH rate calculation */
105 hz = DIV_ROUND_CLOSEST_ULL(100ULL * NSEC_PER_SEC, period_ns);
106 rate = DIV_ROUND_CLOSEST_ULL(100ULL * rate, hz);
107
108 /*
109 * Since the actual PWM divider is the register's frequency divider
110 * field minus 1, we need to decrement to get the correct value to
111 * write to the register.
112 */
113 if (rate > 0)
114 rate--;
115
116 /*
117 * Make sure that the rate will fit in the register's frequency
118 * divider field.
119 */
120 if (rate >> PWM_SCALE_WIDTH)
121 return -EINVAL;
122
123 val |= rate << PWM_SCALE_SHIFT;
124
125 /*
126 * If the PWM channel is disabled, make sure to turn on the clock
127 * before writing the register. Otherwise, keep it enabled.
128 */
129 if (!pwm_is_enabled(pwm)) {
130 err = clk_prepare_enable(pc->clk);
131 if (err < 0)
132 return err;
133 } else
134 val |= PWM_ENABLE;
135
136 pwm_writel(pc, pwm->hwpwm, val);
137
138 /*
139 * If the PWM is not enabled, turn the clock off again to save power.
140 */
141 if (!pwm_is_enabled(pwm))
142 clk_disable_unprepare(pc->clk);
143
144 return 0;
145}
146
147static int tegra_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
148{
149 struct tegra_pwm_chip *pc = to_tegra_pwm_chip(chip);
150 int rc = 0;
151 u32 val;
152
153 rc = clk_prepare_enable(pc->clk);
154 if (rc < 0)
155 return rc;
156
157 val = pwm_readl(pc, pwm->hwpwm);
158 val |= PWM_ENABLE;
159 pwm_writel(pc, pwm->hwpwm, val);
160
161 return 0;
162}
163
164static void tegra_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
165{
166 struct tegra_pwm_chip *pc = to_tegra_pwm_chip(chip);
167 u32 val;
168
169 val = pwm_readl(pc, pwm->hwpwm);
170 val &= ~PWM_ENABLE;
171 pwm_writel(pc, pwm->hwpwm, val);
172
173 clk_disable_unprepare(pc->clk);
174}
175
176static const struct pwm_ops tegra_pwm_ops = {
177 .config = tegra_pwm_config,
178 .enable = tegra_pwm_enable,
179 .disable = tegra_pwm_disable,
180 .owner = THIS_MODULE,
181};
182
183static int tegra_pwm_probe(struct platform_device *pdev)
184{
185 struct tegra_pwm_chip *pwm;
186 struct resource *r;
187 int ret;
188
189 pwm = devm_kzalloc(&pdev->dev, sizeof(*pwm), GFP_KERNEL);
190 if (!pwm)
191 return -ENOMEM;
192
193 pwm->soc = of_device_get_match_data(&pdev->dev);
194 pwm->dev = &pdev->dev;
195
196 r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
197 pwm->regs = devm_ioremap_resource(&pdev->dev, r);
198 if (IS_ERR(pwm->regs))
199 return PTR_ERR(pwm->regs);
200
201 platform_set_drvdata(pdev, pwm);
202
203 pwm->clk = devm_clk_get(&pdev->dev, NULL);
204 if (IS_ERR(pwm->clk))
205 return PTR_ERR(pwm->clk);
206
207 /* Set maximum frequency of the IP */
208 ret = clk_set_rate(pwm->clk, pwm->soc->max_frequency);
209 if (ret < 0) {
210 dev_err(&pdev->dev, "Failed to set max frequency: %d\n", ret);
211 return ret;
212 }
213
214 /*
215 * The requested and configured frequency may differ due to
216 * clock register resolutions. Get the configured frequency
217 * so that PWM period can be calculated more accurately.
218 */
219 pwm->clk_rate = clk_get_rate(pwm->clk);
220
221 pwm->rst = devm_reset_control_get_exclusive(&pdev->dev, "pwm");
222 if (IS_ERR(pwm->rst)) {
223 ret = PTR_ERR(pwm->rst);
224 dev_err(&pdev->dev, "Reset control is not found: %d\n", ret);
225 return ret;
226 }
227
228 reset_control_deassert(pwm->rst);
229
230 pwm->chip.dev = &pdev->dev;
231 pwm->chip.ops = &tegra_pwm_ops;
232 pwm->chip.base = -1;
233 pwm->chip.npwm = pwm->soc->num_channels;
234
235 ret = pwmchip_add(&pwm->chip);
236 if (ret < 0) {
237 dev_err(&pdev->dev, "pwmchip_add() failed: %d\n", ret);
238 reset_control_assert(pwm->rst);
239 return ret;
240 }
241
242 return 0;
243}
244
245static int tegra_pwm_remove(struct platform_device *pdev)
246{
247 struct tegra_pwm_chip *pc = platform_get_drvdata(pdev);
248 unsigned int i;
249 int err;
250
251 if (WARN_ON(!pc))
252 return -ENODEV;
253
254 err = clk_prepare_enable(pc->clk);
255 if (err < 0)
256 return err;
257
258 for (i = 0; i < pc->chip.npwm; i++) {
259 struct pwm_device *pwm = &pc->chip.pwms[i];
260
261 if (!pwm_is_enabled(pwm))
262 if (clk_prepare_enable(pc->clk) < 0)
263 continue;
264
265 pwm_writel(pc, i, 0);
266
267 clk_disable_unprepare(pc->clk);
268 }
269
270 reset_control_assert(pc->rst);
271 clk_disable_unprepare(pc->clk);
272
273 return pwmchip_remove(&pc->chip);
274}
275
276#ifdef CONFIG_PM_SLEEP
277static int tegra_pwm_suspend(struct device *dev)
278{
279 return pinctrl_pm_select_sleep_state(dev);
280}
281
282static int tegra_pwm_resume(struct device *dev)
283{
284 return pinctrl_pm_select_default_state(dev);
285}
286#endif
287
288static const struct tegra_pwm_soc tegra20_pwm_soc = {
289 .num_channels = 4,
290 .max_frequency = 48000000UL,
291};
292
293static const struct tegra_pwm_soc tegra186_pwm_soc = {
294 .num_channels = 1,
295 .max_frequency = 102000000UL,
296};
297
298static const struct of_device_id tegra_pwm_of_match[] = {
299 { .compatible = "nvidia,tegra20-pwm", .data = &tegra20_pwm_soc },
300 { .compatible = "nvidia,tegra186-pwm", .data = &tegra186_pwm_soc },
301 { }
302};
303
304MODULE_DEVICE_TABLE(of, tegra_pwm_of_match);
305
306static const struct dev_pm_ops tegra_pwm_pm_ops = {
307 SET_SYSTEM_SLEEP_PM_OPS(tegra_pwm_suspend, tegra_pwm_resume)
308};
309
310static struct platform_driver tegra_pwm_driver = {
311 .driver = {
312 .name = "tegra-pwm",
313 .of_match_table = tegra_pwm_of_match,
314 .pm = &tegra_pwm_pm_ops,
315 },
316 .probe = tegra_pwm_probe,
317 .remove = tegra_pwm_remove,
318};
319
320module_platform_driver(tegra_pwm_driver);
321
322MODULE_LICENSE("GPL");
323MODULE_AUTHOR("NVIDIA Corporation");
324MODULE_ALIAS("platform:tegra-pwm");