summaryrefslogtreecommitdiffstats
path: root/drivers/pwm/pwm-bcm-kona.c
blob: 8c85c66ea5c9eac9c0c2eb5de0f73d61045855fd (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
/*
 * Copyright (C) 2014 Broadcom Corporation
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation version 2.
 *
 * This program is distributed "as is" WITHOUT ANY WARRANTY of any
 * kind, whether express or implied; without even the implied warranty
 * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 */

#include <linux/clk.h>
#include <linux/delay.h>
#include <linux/err.h>
#include <linux/io.h>
#include <linux/ioport.h>
#include <linux/math64.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/pwm.h>
#include <linux/slab.h>
#include <linux/types.h>

/*
 * The Kona PWM has some unusual characteristics.  Here are the main points.
 *
 * 1) There is no disable bit and the hardware docs advise programming a zero
 *    duty to achieve output equivalent to that of a normal disable operation.
 *
 * 2) Changes to prescale, duty, period, and polarity do not take effect until
 *    a subsequent rising edge of the trigger bit.
 *
 * 3) If the smooth bit and trigger bit are both low, the output is a constant
 *    high signal.  Otherwise, the earlier waveform continues to be output.
 *
 * 4) If the smooth bit is set on the rising edge of the trigger bit, output
 *    will transition to the new settings on a period boundary (which could be
 *    seconds away).  If the smooth bit is clear, new settings will be applied
 *    as soon as possible (the hardware always has a 400ns delay).
 *
 * 5) When the external clock that feeds the PWM is disabled, output is pegged
 *    high or low depending on its state at that exact instant.
 */

#define PWM_CONTROL_OFFSET			0x00000000
#define PWM_CONTROL_SMOOTH_SHIFT(chan)		(24 + (chan))
#define PWM_CONTROL_TYPE_SHIFT(chan)		(16 + (chan))
#define PWM_CONTROL_POLARITY_SHIFT(chan)	(8 + (chan))
#define PWM_CONTROL_TRIGGER_SHIFT(chan)		(chan)

#define PRESCALE_OFFSET				0x00000004
#define PRESCALE_SHIFT(chan)			((chan) << 2)
#define PRESCALE_MASK(chan)			(0x7 << PRESCALE_SHIFT(chan))
#define PRESCALE_MIN				0x00000000
#define PRESCALE_MAX				0x00000007

#define PERIOD_COUNT_OFFSET(chan)		(0x00000008 + ((chan) << 3))
#define PERIOD_COUNT_MIN			0x00000002
#define PERIOD_COUNT_MAX			0x00ffffff

#define DUTY_CYCLE_HIGH_OFFSET(chan)		(0x0000000c + ((chan) << 3))
#define DUTY_CYCLE_HIGH_MIN			0x00000000
#define DUTY_CYCLE_HIGH_MAX			0x00ffffff

struct kona_pwmc {
	struct pwm_chip chip;
	void __iomem *base;
	struct clk *clk;
};

static inline struct kona_pwmc *to_kona_pwmc(struct pwm_chip *_chip)
{
	return container_of(_chip, struct kona_pwmc, chip);
}

/*
 * Clear trigger bit but set smooth bit to maintain old output.
 */
static void kona_pwmc_prepare_for_settings(struct kona_pwmc *kp,
	unsigned int chan)
{
	unsigned int value = readl(kp->base + PWM_CONTROL_OFFSET);

	value |= 1 << PWM_CONTROL_SMOOTH_SHIFT(chan);
	value &= ~(1 << PWM_CONTROL_TRIGGER_SHIFT(chan));
	writel(value, kp->base + PWM_CONTROL_OFFSET);

	/*
	 * There must be a min 400ns delay between clearing trigger and setting
	 * it. Failing to do this may result in no PWM signal.
	 */
	ndelay(400);
}

static void kona_pwmc_apply_settings(struct kona_pwmc *kp, unsigned int chan)
{
	unsigned int value = readl(kp->base + PWM_CONTROL_OFFSET);

	/* Set trigger bit and clear smooth bit to apply new settings */
	value &= ~(1 << PWM_CONTROL_SMOOTH_SHIFT(chan));
	value |= 1 << PWM_CONTROL_TRIGGER_SHIFT(chan);
	writel(value, kp->base + PWM_CONTROL_OFFSET);

	/* Trigger bit must be held high for at least 400 ns. */
	ndelay(400);
}

static int kona_pwmc_config(struct pwm_chip *chip, struct pwm_device *pwm,
			    int duty_ns, int period_ns)
{
	struct kona_pwmc *kp = to_kona_pwmc(chip);
	u64 val, div, rate;
	unsigned long prescale = PRESCALE_MIN, pc, dc;
	unsigned int value, chan = pwm->hwpwm;

	/*
	 * Find period count, duty count and prescale to suit duty_ns and
	 * period_ns. This is done according to formulas described below:
	 *
	 * period_ns = 10^9 * (PRESCALE + 1) * PC / PWM_CLK_RATE
	 * duty_ns = 10^9 * (PRESCALE + 1) * DC / PWM_CLK_RATE
	 *
	 * PC = (PWM_CLK_RATE * period_ns) / (10^9 * (PRESCALE + 1))
	 * DC = (PWM_CLK_RATE * duty_ns) / (10^9 * (PRESCALE + 1))
	 */

	rate = clk_get_rate(kp->clk);

	while (1) {
		div = 1000000000;
		div *= 1 + prescale;
		val = rate * period_ns;
		pc = div64_u64(val, div);
		val = rate * duty_ns;
		dc = div64_u64(val, div);

		/* If duty_ns or period_ns are not achievable then return */
		if (pc < PERIOD_COUNT_MIN)
			return -EINVAL;

		/* If pc and dc are in bounds, the calculation is done */
		if (pc <= PERIOD_COUNT_MAX && dc <= DUTY_CYCLE_HIGH_MAX)
			break;

		/* Otherwise, increase prescale and recalculate pc and dc */
		if (++prescale > PRESCALE_MAX)
			return -EINVAL;
	}

	/*
	 * Don't apply settings if disabled. The period and duty cycle are
	 * always calculated above to ensure the new values are
	 * validated immediately instead of on enable.
	 */
	if (pwm_is_enabled(pwm)) {
		kona_pwmc_prepare_for_settings(kp, chan);

		value = readl(kp->base + PRESCALE_OFFSET);
		value &= ~PRESCALE_MASK(chan);
		value |= prescale << PRESCALE_SHIFT(chan);
		writel(value, kp->base + PRESCALE_OFFSET);

		writel(pc, kp->base + PERIOD_COUNT_OFFSET(chan));

		writel(dc, kp->base + DUTY_CYCLE_HIGH_OFFSET(chan));

		kona_pwmc_apply_settings(kp, chan);
	}

	return 0;
}

static int kona_pwmc_set_polarity(struct pwm_chip *chip, struct pwm_device *pwm,
				  enum pwm_polarity polarity)
{
	struct kona_pwmc *kp = to_kona_pwmc(chip);
	unsigned int chan = pwm->hwpwm;
	unsigned int value;
	int ret;

	ret = clk_prepare_enable(kp->clk);
	if (ret < 0) {
		dev_err(chip->dev, "failed to enable clock: %d\n", ret);
		return ret;
	}

	kona_pwmc_prepare_for_settings(kp, chan);

	value = readl(kp->base + PWM_CONTROL_OFFSET);

	if (polarity == PWM_POLARITY_NORMAL)
		value |= 1 << PWM_CONTROL_POLARITY_SHIFT(chan);
	else
		value &= ~(1 << PWM_CONTROL_POLARITY_SHIFT(chan));

	writel(value, kp->base + PWM_CONTROL_OFFSET);

	kona_pwmc_apply_settings(kp, chan);

	clk_disable_unprepare(kp->clk);

	return 0;
}

static int kona_pwmc_enable(struct pwm_chip *chip, struct pwm_device *pwm)
{
	struct kona_pwmc *kp = to_kona_pwmc(chip);
	int ret;

	ret = clk_prepare_enable(kp->clk);
	if (ret < 0) {
		dev_err(chip->dev, "failed to enable clock: %d\n", ret);
		return ret;
	}

	ret = kona_pwmc_config(chip, pwm, pwm_get_duty_cycle(pwm),
			       pwm_get_period(pwm));
	if (ret < 0) {
		clk_disable_unprepare(kp->clk);
		return ret;
	}

	return 0;
}

static void kona_pwmc_disable(struct pwm_chip *chip, struct pwm_device *pwm)
{
	struct kona_pwmc *kp = to_kona_pwmc(chip);
	unsigned int chan = pwm->hwpwm;
	unsigned int value;

	kona_pwmc_prepare_for_settings(kp, chan);

	/* Simulate a disable by configuring for zero duty */
	writel(0, kp->base + DUTY_CYCLE_HIGH_OFFSET(chan));
	writel(0, kp->base + PERIOD_COUNT_OFFSET(chan));

	/* Set prescale to 0 for this channel */
	value = readl(kp->base + PRESCALE_OFFSET);
	value &= ~PRESCALE_MASK(chan);
	writel(value, kp->base + PRESCALE_OFFSET);

	kona_pwmc_apply_settings(kp, chan);

	clk_disable_unprepare(kp->clk);
}

static const struct pwm_ops kona_pwm_ops = {
	.config = kona_pwmc_config,
	.set_polarity = kona_pwmc_set_polarity,
	.enable = kona_pwmc_enable,
	.disable = kona_pwmc_disable,
	.owner = THIS_MODULE,
};

static int kona_pwmc_probe(struct platform_device *pdev)
{
	struct kona_pwmc *kp;
	unsigned int chan;
	unsigned int value = 0;
	int ret = 0;

	kp = devm_kzalloc(&pdev->dev, sizeof(*kp), GFP_KERNEL);
	if (kp == NULL)
		return -ENOMEM;

	platform_set_drvdata(pdev, kp);

	kp->chip.dev = &pdev->dev;
	kp->chip.ops = &kona_pwm_ops;
	kp->chip.npwm = 6;

	kp->base = devm_platform_ioremap_resource(pdev, 0);
	if (IS_ERR(kp->base))
		return PTR_ERR(kp->base);

	kp->clk = devm_clk_get(&pdev->dev, NULL);
	if (IS_ERR(kp->clk)) {
		dev_err(&pdev->dev, "failed to get clock: %ld\n",
			PTR_ERR(kp->clk));
		return PTR_ERR(kp->clk);
	}

	ret = clk_prepare_enable(kp->clk);
	if (ret < 0) {
		dev_err(&pdev->dev, "failed to enable clock: %d\n", ret);
		return ret;
	}

	/* Set push/pull for all channels */
	for (chan = 0; chan < kp->chip.npwm; chan++)
		value |= (1 << PWM_CONTROL_TYPE_SHIFT(chan));

	writel(value, kp->base + PWM_CONTROL_OFFSET);

	clk_disable_unprepare(kp->clk);

	ret = pwmchip_add(&kp->chip);
	if (ret < 0)
		dev_err(&pdev->dev, "failed to add PWM chip: %d\n", ret);

	return ret;
}

static int kona_pwmc_remove(struct platform_device *pdev)
{
	struct kona_pwmc *kp = platform_get_drvdata(pdev);

	return pwmchip_remove(&kp->chip);
}

static const struct of_device_id bcm_kona_pwmc_dt[] = {
	{ .compatible = "brcm,kona-pwm" },
	{ },
};
MODULE_DEVICE_TABLE(of, bcm_kona_pwmc_dt);

static struct platform_driver kona_pwmc_driver = {
	.driver = {
		.name = "bcm-kona-pwm",
		.of_match_table = bcm_kona_pwmc_dt,
	},
	.probe = kona_pwmc_probe,
	.remove = kona_pwmc_remove,
};
module_platform_driver(kona_pwmc_driver);

MODULE_AUTHOR("Broadcom Corporation <bcm-kernel-feedback-list@broadcom.com>");
MODULE_AUTHOR("Tim Kryger <tkryger@broadcom.com>");
MODULE_DESCRIPTION("Broadcom Kona PWM driver");
MODULE_LICENSE("GPL v2");