xref: /openbmc/linux/drivers/pwm/pwm-stmpe.c (revision b2c71e9f)
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * Copyright (C) 2016 Linaro Ltd.
4  *
5  * Author: Linus Walleij <linus.walleij@linaro.org>
6  */
7 
8 #include <linux/bitops.h>
9 #include <linux/delay.h>
10 #include <linux/err.h>
11 #include <linux/mfd/stmpe.h>
12 #include <linux/module.h>
13 #include <linux/of.h>
14 #include <linux/platform_device.h>
15 #include <linux/pwm.h>
16 #include <linux/slab.h>
17 
18 #define STMPE24XX_PWMCS		0x30
19 #define PWMCS_EN_PWM0		BIT(0)
20 #define PWMCS_EN_PWM1		BIT(1)
21 #define PWMCS_EN_PWM2		BIT(2)
22 #define STMPE24XX_PWMIC0	0x38
23 #define STMPE24XX_PWMIC1	0x39
24 #define STMPE24XX_PWMIC2	0x3a
25 
26 #define STMPE_PWM_24XX_PINBASE	21
27 
28 struct stmpe_pwm {
29 	struct stmpe *stmpe;
30 	struct pwm_chip chip;
31 	u8 last_duty;
32 };
33 
to_stmpe_pwm(struct pwm_chip * chip)34 static inline struct stmpe_pwm *to_stmpe_pwm(struct pwm_chip *chip)
35 {
36 	return container_of(chip, struct stmpe_pwm, chip);
37 }
38 
stmpe_24xx_pwm_enable(struct pwm_chip * chip,struct pwm_device * pwm)39 static int stmpe_24xx_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
40 {
41 	struct stmpe_pwm *stmpe_pwm = to_stmpe_pwm(chip);
42 	u8 value;
43 	int ret;
44 
45 	ret = stmpe_reg_read(stmpe_pwm->stmpe, STMPE24XX_PWMCS);
46 	if (ret < 0) {
47 		dev_err(chip->dev, "error reading PWM#%u control\n",
48 			pwm->hwpwm);
49 		return ret;
50 	}
51 
52 	value = ret | BIT(pwm->hwpwm);
53 
54 	ret = stmpe_reg_write(stmpe_pwm->stmpe, STMPE24XX_PWMCS, value);
55 	if (ret) {
56 		dev_err(chip->dev, "error writing PWM#%u control\n",
57 			pwm->hwpwm);
58 		return ret;
59 	}
60 
61 	return 0;
62 }
63 
stmpe_24xx_pwm_disable(struct pwm_chip * chip,struct pwm_device * pwm)64 static int stmpe_24xx_pwm_disable(struct pwm_chip *chip,
65 				  struct pwm_device *pwm)
66 {
67 	struct stmpe_pwm *stmpe_pwm = to_stmpe_pwm(chip);
68 	u8 value;
69 	int ret;
70 
71 	ret = stmpe_reg_read(stmpe_pwm->stmpe, STMPE24XX_PWMCS);
72 	if (ret < 0) {
73 		dev_err(chip->dev, "error reading PWM#%u control\n",
74 			pwm->hwpwm);
75 		return ret;
76 	}
77 
78 	value = ret & ~BIT(pwm->hwpwm);
79 
80 	ret = stmpe_reg_write(stmpe_pwm->stmpe, STMPE24XX_PWMCS, value);
81 	if (ret)
82 		dev_err(chip->dev, "error writing PWM#%u control\n",
83 			pwm->hwpwm);
84 	return ret;
85 }
86 
87 /* STMPE 24xx PWM instructions */
88 #define SMAX		0x007f
89 #define SMIN		0x00ff
90 #define GTS		0x0000
91 #define LOAD		BIT(14) /* Only available on 2403 */
92 #define RAMPUP		0x0000
93 #define RAMPDOWN	BIT(7)
94 #define PRESCALE_512	BIT(14)
95 #define STEPTIME_1	BIT(8)
96 #define BRANCH		(BIT(15) | BIT(13))
97 
stmpe_24xx_pwm_config(struct pwm_chip * chip,struct pwm_device * pwm,int duty_ns,int period_ns)98 static int stmpe_24xx_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
99 				 int duty_ns, int period_ns)
100 {
101 	struct stmpe_pwm *stmpe_pwm = to_stmpe_pwm(chip);
102 	unsigned int i, pin;
103 	u16 program[3] = {
104 		SMAX,
105 		GTS,
106 		GTS,
107 	};
108 	u8 offset;
109 	int ret;
110 
111 	/* Make sure we are disabled */
112 	if (pwm_is_enabled(pwm)) {
113 		ret = stmpe_24xx_pwm_disable(chip, pwm);
114 		if (ret)
115 			return ret;
116 	} else {
117 		/* Connect the PWM to the pin */
118 		pin = pwm->hwpwm;
119 
120 		/* On STMPE2401 and 2403 pins 21,22,23 are used */
121 		if (stmpe_pwm->stmpe->partnum == STMPE2401 ||
122 		    stmpe_pwm->stmpe->partnum == STMPE2403)
123 			pin += STMPE_PWM_24XX_PINBASE;
124 
125 		ret = stmpe_set_altfunc(stmpe_pwm->stmpe, BIT(pin),
126 					STMPE_BLOCK_PWM);
127 		if (ret) {
128 			dev_err(chip->dev, "unable to connect PWM#%u to pin\n",
129 				pwm->hwpwm);
130 			return ret;
131 		}
132 	}
133 
134 	/* STMPE24XX */
135 	switch (pwm->hwpwm) {
136 	case 0:
137 		offset = STMPE24XX_PWMIC0;
138 		break;
139 
140 	case 1:
141 		offset = STMPE24XX_PWMIC1;
142 		break;
143 
144 	case 2:
145 		offset = STMPE24XX_PWMIC2;
146 		break;
147 
148 	default:
149 		/* Should not happen as npwm is 3 */
150 		return -ENODEV;
151 	}
152 
153 	dev_dbg(chip->dev, "PWM#%u: config duty %d ns, period %d ns\n",
154 		pwm->hwpwm, duty_ns, period_ns);
155 
156 	if (duty_ns == 0) {
157 		if (stmpe_pwm->stmpe->partnum == STMPE2401)
158 			program[0] = SMAX; /* off all the time */
159 
160 		if (stmpe_pwm->stmpe->partnum == STMPE2403)
161 			program[0] = LOAD | 0xff; /* LOAD 0xff */
162 
163 		stmpe_pwm->last_duty = 0x00;
164 	} else if (duty_ns == period_ns) {
165 		if (stmpe_pwm->stmpe->partnum == STMPE2401)
166 			program[0] = SMIN; /* on all the time */
167 
168 		if (stmpe_pwm->stmpe->partnum == STMPE2403)
169 			program[0] = LOAD | 0x00; /* LOAD 0x00 */
170 
171 		stmpe_pwm->last_duty = 0xff;
172 	} else {
173 		u8 value, last = stmpe_pwm->last_duty;
174 		unsigned long duty;
175 
176 		/*
177 		 * Counter goes from 0x00 to 0xff repeatedly at 32768 Hz,
178 		 * (means a period of 30517 ns) then this is compared to the
179 		 * counter from the ramp, if this is >= PWM counter the output
180 		 * is high. With LOAD we can define how much of the cycle it
181 		 * is on.
182 		 *
183 		 * Prescale = 0 -> 2 kHz -> T = 1/f = 488281.25 ns
184 		 */
185 
186 		/* Scale to 0..0xff */
187 		duty = duty_ns * 256;
188 		duty = DIV_ROUND_CLOSEST(duty, period_ns);
189 		value = duty;
190 
191 		if (value == last) {
192 			/* Run the old program */
193 			if (pwm_is_enabled(pwm))
194 				stmpe_24xx_pwm_enable(chip, pwm);
195 
196 			return 0;
197 		} else if (stmpe_pwm->stmpe->partnum == STMPE2403) {
198 			/* STMPE2403 can simply set the right PWM value */
199 			program[0] = LOAD | value;
200 			program[1] = 0x0000;
201 		} else if (stmpe_pwm->stmpe->partnum == STMPE2401) {
202 			/* STMPE2401 need a complex program */
203 			u16 incdec = 0x0000;
204 
205 			if (last < value)
206 				/* Count up */
207 				incdec = RAMPUP | (value - last);
208 			else
209 				/* Count down */
210 				incdec = RAMPDOWN | (last - value);
211 
212 			/* Step to desired value, smoothly */
213 			program[0] = PRESCALE_512 | STEPTIME_1 | incdec;
214 
215 			/* Loop eternally to 0x00 */
216 			program[1] = BRANCH;
217 		}
218 
219 		dev_dbg(chip->dev,
220 			"PWM#%u: value = %02x, last_duty = %02x, program=%04x,%04x,%04x\n",
221 			pwm->hwpwm, value, last, program[0], program[1],
222 			program[2]);
223 		stmpe_pwm->last_duty = value;
224 	}
225 
226 	/*
227 	 * We can write programs of up to 64 16-bit words into this channel.
228 	 */
229 	for (i = 0; i < ARRAY_SIZE(program); i++) {
230 		u8 value;
231 
232 		value = (program[i] >> 8) & 0xff;
233 
234 		ret = stmpe_reg_write(stmpe_pwm->stmpe, offset, value);
235 		if (ret) {
236 			dev_err(chip->dev, "error writing register %02x: %d\n",
237 				offset, ret);
238 			return ret;
239 		}
240 
241 		value = program[i] & 0xff;
242 
243 		ret = stmpe_reg_write(stmpe_pwm->stmpe, offset, value);
244 		if (ret) {
245 			dev_err(chip->dev, "error writing register %02x: %d\n",
246 				offset, ret);
247 			return ret;
248 		}
249 	}
250 
251 	/* If we were enabled, re-enable this PWM */
252 	if (pwm_is_enabled(pwm))
253 		stmpe_24xx_pwm_enable(chip, pwm);
254 
255 	/* Sleep for 200ms so we're sure it will take effect */
256 	msleep(200);
257 
258 	dev_dbg(chip->dev, "programmed PWM#%u, %u bytes\n", pwm->hwpwm, i);
259 
260 	return 0;
261 }
262 
stmpe_24xx_pwm_apply(struct pwm_chip * chip,struct pwm_device * pwm,const struct pwm_state * state)263 static int stmpe_24xx_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
264 				const struct pwm_state *state)
265 {
266 	int err;
267 
268 	if (state->polarity != PWM_POLARITY_NORMAL)
269 		return -EINVAL;
270 
271 	if (!state->enabled) {
272 		if (pwm->state.enabled)
273 			return stmpe_24xx_pwm_disable(chip, pwm);
274 
275 		return 0;
276 	}
277 
278 	err = stmpe_24xx_pwm_config(pwm->chip, pwm, state->duty_cycle, state->period);
279 	if (err)
280 		return err;
281 
282 	if (!pwm->state.enabled)
283 		err = stmpe_24xx_pwm_enable(chip, pwm);
284 
285 	return err;
286 }
287 
288 static const struct pwm_ops stmpe_24xx_pwm_ops = {
289 	.apply = stmpe_24xx_pwm_apply,
290 	.owner = THIS_MODULE,
291 };
292 
stmpe_pwm_probe(struct platform_device * pdev)293 static int __init stmpe_pwm_probe(struct platform_device *pdev)
294 {
295 	struct stmpe *stmpe = dev_get_drvdata(pdev->dev.parent);
296 	struct stmpe_pwm *stmpe_pwm;
297 	int ret;
298 
299 	stmpe_pwm = devm_kzalloc(&pdev->dev, sizeof(*stmpe_pwm), GFP_KERNEL);
300 	if (!stmpe_pwm)
301 		return -ENOMEM;
302 
303 	stmpe_pwm->stmpe = stmpe;
304 	stmpe_pwm->chip.dev = &pdev->dev;
305 
306 	if (stmpe->partnum == STMPE2401 || stmpe->partnum == STMPE2403) {
307 		stmpe_pwm->chip.ops = &stmpe_24xx_pwm_ops;
308 		stmpe_pwm->chip.npwm = 3;
309 	} else {
310 		if (stmpe->partnum == STMPE1601)
311 			dev_err(&pdev->dev, "STMPE1601 not yet supported\n");
312 		else
313 			dev_err(&pdev->dev, "Unknown STMPE PWM\n");
314 
315 		return -ENODEV;
316 	}
317 
318 	ret = stmpe_enable(stmpe, STMPE_BLOCK_PWM);
319 	if (ret)
320 		return ret;
321 
322 	ret = pwmchip_add(&stmpe_pwm->chip);
323 	if (ret) {
324 		stmpe_disable(stmpe, STMPE_BLOCK_PWM);
325 		return ret;
326 	}
327 
328 	return 0;
329 }
330 
331 static struct platform_driver stmpe_pwm_driver = {
332 	.driver = {
333 		.name = "stmpe-pwm",
334 	},
335 };
336 builtin_platform_driver_probe(stmpe_pwm_driver, stmpe_pwm_probe);
337