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 void 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;
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;
85 	}
86 }
87 
88 /* STMPE 24xx PWM instructions */
89 #define SMAX		0x007f
90 #define SMIN		0x00ff
91 #define GTS		0x0000
92 #define LOAD		BIT(14) /* Only available on 2403 */
93 #define RAMPUP		0x0000
94 #define RAMPDOWN	BIT(7)
95 #define PRESCALE_512	BIT(14)
96 #define STEPTIME_1	BIT(8)
97 #define BRANCH		(BIT(15) | BIT(13))
98 
stmpe_24xx_pwm_config(struct pwm_chip * chip,struct pwm_device * pwm,int duty_ns,int period_ns)99 static int stmpe_24xx_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
100 				 int duty_ns, int period_ns)
101 {
102 	struct stmpe_pwm *stmpe_pwm = to_stmpe_pwm(chip);
103 	unsigned int i, pin;
104 	u16 program[3] = {
105 		SMAX,
106 		GTS,
107 		GTS,
108 	};
109 	u8 offset;
110 	int ret;
111 
112 	/* Make sure we are disabled */
113 	if (pwm_is_enabled(pwm)) {
114 		stmpe_24xx_pwm_disable(chip, pwm);
115 	} else {
116 		/* Connect the PWM to the pin */
117 		pin = pwm->hwpwm;
118 
119 		/* On STMPE2401 and 2403 pins 21,22,23 are used */
120 		if (stmpe_pwm->stmpe->partnum == STMPE2401 ||
121 		    stmpe_pwm->stmpe->partnum == STMPE2403)
122 			pin += STMPE_PWM_24XX_PINBASE;
123 
124 		ret = stmpe_set_altfunc(stmpe_pwm->stmpe, BIT(pin),
125 					STMPE_BLOCK_PWM);
126 		if (ret) {
127 			dev_err(chip->dev, "unable to connect PWM#%u to pin\n",
128 				pwm->hwpwm);
129 			return ret;
130 		}
131 	}
132 
133 	/* STMPE24XX */
134 	switch (pwm->hwpwm) {
135 	case 0:
136 		offset = STMPE24XX_PWMIC0;
137 		break;
138 
139 	case 1:
140 		offset = STMPE24XX_PWMIC1;
141 		break;
142 
143 	case 2:
144 		offset = STMPE24XX_PWMIC2;
145 		break;
146 
147 	default:
148 		/* Should not happen as npwm is 3 */
149 		return -ENODEV;
150 	}
151 
152 	dev_dbg(chip->dev, "PWM#%u: config duty %d ns, period %d ns\n",
153 		pwm->hwpwm, duty_ns, period_ns);
154 
155 	if (duty_ns == 0) {
156 		if (stmpe_pwm->stmpe->partnum == STMPE2401)
157 			program[0] = SMAX; /* off all the time */
158 
159 		if (stmpe_pwm->stmpe->partnum == STMPE2403)
160 			program[0] = LOAD | 0xff; /* LOAD 0xff */
161 
162 		stmpe_pwm->last_duty = 0x00;
163 	} else if (duty_ns == period_ns) {
164 		if (stmpe_pwm->stmpe->partnum == STMPE2401)
165 			program[0] = SMIN; /* on all the time */
166 
167 		if (stmpe_pwm->stmpe->partnum == STMPE2403)
168 			program[0] = LOAD | 0x00; /* LOAD 0x00 */
169 
170 		stmpe_pwm->last_duty = 0xff;
171 	} else {
172 		u8 value, last = stmpe_pwm->last_duty;
173 		unsigned long duty;
174 
175 		/*
176 		 * Counter goes from 0x00 to 0xff repeatedly at 32768 Hz,
177 		 * (means a period of 30517 ns) then this is compared to the
178 		 * counter from the ramp, if this is >= PWM counter the output
179 		 * is high. With LOAD we can define how much of the cycle it
180 		 * is on.
181 		 *
182 		 * Prescale = 0 -> 2 kHz -> T = 1/f = 488281.25 ns
183 		 */
184 
185 		/* Scale to 0..0xff */
186 		duty = duty_ns * 256;
187 		duty = DIV_ROUND_CLOSEST(duty, period_ns);
188 		value = duty;
189 
190 		if (value == last) {
191 			/* Run the old program */
192 			if (pwm_is_enabled(pwm))
193 				stmpe_24xx_pwm_enable(chip, pwm);
194 
195 			return 0;
196 		} else if (stmpe_pwm->stmpe->partnum == STMPE2403) {
197 			/* STMPE2403 can simply set the right PWM value */
198 			program[0] = LOAD | value;
199 			program[1] = 0x0000;
200 		} else if (stmpe_pwm->stmpe->partnum == STMPE2401) {
201 			/* STMPE2401 need a complex program */
202 			u16 incdec = 0x0000;
203 
204 			if (last < value)
205 				/* Count up */
206 				incdec = RAMPUP | (value - last);
207 			else
208 				/* Count down */
209 				incdec = RAMPDOWN | (last - value);
210 
211 			/* Step to desired value, smoothly */
212 			program[0] = PRESCALE_512 | STEPTIME_1 | incdec;
213 
214 			/* Loop eternally to 0x00 */
215 			program[1] = BRANCH;
216 		}
217 
218 		dev_dbg(chip->dev,
219 			"PWM#%u: value = %02x, last_duty = %02x, program=%04x,%04x,%04x\n",
220 			pwm->hwpwm, value, last, program[0], program[1],
221 			program[2]);
222 		stmpe_pwm->last_duty = value;
223 	}
224 
225 	/*
226 	 * We can write programs of up to 64 16-bit words into this channel.
227 	 */
228 	for (i = 0; i < ARRAY_SIZE(program); i++) {
229 		u8 value;
230 
231 		value = (program[i] >> 8) & 0xff;
232 
233 		ret = stmpe_reg_write(stmpe_pwm->stmpe, offset, value);
234 		if (ret) {
235 			dev_err(chip->dev, "error writing register %02x: %d\n",
236 				offset, ret);
237 			return ret;
238 		}
239 
240 		value = program[i] & 0xff;
241 
242 		ret = stmpe_reg_write(stmpe_pwm->stmpe, offset, value);
243 		if (ret) {
244 			dev_err(chip->dev, "error writing register %02x: %d\n",
245 				offset, ret);
246 			return ret;
247 		}
248 	}
249 
250 	/* If we were enabled, re-enable this PWM */
251 	if (pwm_is_enabled(pwm))
252 		stmpe_24xx_pwm_enable(chip, pwm);
253 
254 	/* Sleep for 200ms so we're sure it will take effect */
255 	msleep(200);
256 
257 	dev_dbg(chip->dev, "programmed PWM#%u, %u bytes\n", pwm->hwpwm, i);
258 
259 	return 0;
260 }
261 
262 static const struct pwm_ops stmpe_24xx_pwm_ops = {
263 	.config = stmpe_24xx_pwm_config,
264 	.enable = stmpe_24xx_pwm_enable,
265 	.disable = stmpe_24xx_pwm_disable,
266 	.owner = THIS_MODULE,
267 };
268 
stmpe_pwm_probe(struct platform_device * pdev)269 static int __init stmpe_pwm_probe(struct platform_device *pdev)
270 {
271 	struct stmpe *stmpe = dev_get_drvdata(pdev->dev.parent);
272 	struct stmpe_pwm *pwm;
273 	int ret;
274 
275 	pwm = devm_kzalloc(&pdev->dev, sizeof(*pwm), GFP_KERNEL);
276 	if (!pwm)
277 		return -ENOMEM;
278 
279 	pwm->stmpe = stmpe;
280 	pwm->chip.dev = &pdev->dev;
281 
282 	if (stmpe->partnum == STMPE2401 || stmpe->partnum == STMPE2403) {
283 		pwm->chip.ops = &stmpe_24xx_pwm_ops;
284 		pwm->chip.npwm = 3;
285 	} else {
286 		if (stmpe->partnum == STMPE1601)
287 			dev_err(&pdev->dev, "STMPE1601 not yet supported\n");
288 		else
289 			dev_err(&pdev->dev, "Unknown STMPE PWM\n");
290 
291 		return -ENODEV;
292 	}
293 
294 	ret = stmpe_enable(stmpe, STMPE_BLOCK_PWM);
295 	if (ret)
296 		return ret;
297 
298 	ret = pwmchip_add(&pwm->chip);
299 	if (ret) {
300 		stmpe_disable(stmpe, STMPE_BLOCK_PWM);
301 		return ret;
302 	}
303 
304 	platform_set_drvdata(pdev, pwm);
305 
306 	return 0;
307 }
308 
309 static struct platform_driver stmpe_pwm_driver = {
310 	.driver = {
311 		.name = "stmpe-pwm",
312 	},
313 };
314 builtin_platform_driver_probe(stmpe_pwm_driver, stmpe_pwm_probe);
315