1 // SPDX-License-Identifier: GPL-2.0-only
2 // Copyright (C) 2014 Broadcom Corporation
3
4 #include <linux/clk.h>
5 #include <linux/delay.h>
6 #include <linux/err.h>
7 #include <linux/io.h>
8 #include <linux/ioport.h>
9 #include <linux/math64.h>
10 #include <linux/module.h>
11 #include <linux/of.h>
12 #include <linux/platform_device.h>
13 #include <linux/pwm.h>
14 #include <linux/slab.h>
15 #include <linux/types.h>
16
17 /*
18 * The Kona PWM has some unusual characteristics. Here are the main points.
19 *
20 * 1) There is no disable bit and the hardware docs advise programming a zero
21 * duty to achieve output equivalent to that of a normal disable operation.
22 *
23 * 2) Changes to prescale, duty, period, and polarity do not take effect until
24 * a subsequent rising edge of the trigger bit.
25 *
26 * 3) If the smooth bit and trigger bit are both low, the output is a constant
27 * high signal. Otherwise, the earlier waveform continues to be output.
28 *
29 * 4) If the smooth bit is set on the rising edge of the trigger bit, output
30 * will transition to the new settings on a period boundary (which could be
31 * seconds away). If the smooth bit is clear, new settings will be applied
32 * as soon as possible (the hardware always has a 400ns delay).
33 *
34 * 5) When the external clock that feeds the PWM is disabled, output is pegged
35 * high or low depending on its state at that exact instant.
36 */
37
38 #define PWM_CONTROL_OFFSET 0x00000000
39 #define PWM_CONTROL_SMOOTH_SHIFT(chan) (24 + (chan))
40 #define PWM_CONTROL_TYPE_SHIFT(chan) (16 + (chan))
41 #define PWM_CONTROL_POLARITY_SHIFT(chan) (8 + (chan))
42 #define PWM_CONTROL_TRIGGER_SHIFT(chan) (chan)
43
44 #define PRESCALE_OFFSET 0x00000004
45 #define PRESCALE_SHIFT(chan) ((chan) << 2)
46 #define PRESCALE_MASK(chan) (0x7 << PRESCALE_SHIFT(chan))
47 #define PRESCALE_MIN 0x00000000
48 #define PRESCALE_MAX 0x00000007
49
50 #define PERIOD_COUNT_OFFSET(chan) (0x00000008 + ((chan) << 3))
51 #define PERIOD_COUNT_MIN 0x00000002
52 #define PERIOD_COUNT_MAX 0x00ffffff
53
54 #define DUTY_CYCLE_HIGH_OFFSET(chan) (0x0000000c + ((chan) << 3))
55 #define DUTY_CYCLE_HIGH_MIN 0x00000000
56 #define DUTY_CYCLE_HIGH_MAX 0x00ffffff
57
58 struct kona_pwmc {
59 struct pwm_chip chip;
60 void __iomem *base;
61 struct clk *clk;
62 };
63
to_kona_pwmc(struct pwm_chip * chip)64 static inline struct kona_pwmc *to_kona_pwmc(struct pwm_chip *chip)
65 {
66 return container_of(chip, struct kona_pwmc, chip);
67 }
68
69 /*
70 * Clear trigger bit but set smooth bit to maintain old output.
71 */
kona_pwmc_prepare_for_settings(struct kona_pwmc * kp,unsigned int chan)72 static void kona_pwmc_prepare_for_settings(struct kona_pwmc *kp,
73 unsigned int chan)
74 {
75 unsigned int value = readl(kp->base + PWM_CONTROL_OFFSET);
76
77 value |= 1 << PWM_CONTROL_SMOOTH_SHIFT(chan);
78 value &= ~(1 << PWM_CONTROL_TRIGGER_SHIFT(chan));
79 writel(value, kp->base + PWM_CONTROL_OFFSET);
80
81 /*
82 * There must be a min 400ns delay between clearing trigger and setting
83 * it. Failing to do this may result in no PWM signal.
84 */
85 ndelay(400);
86 }
87
kona_pwmc_apply_settings(struct kona_pwmc * kp,unsigned int chan)88 static void kona_pwmc_apply_settings(struct kona_pwmc *kp, unsigned int chan)
89 {
90 unsigned int value = readl(kp->base + PWM_CONTROL_OFFSET);
91
92 /* Set trigger bit and clear smooth bit to apply new settings */
93 value &= ~(1 << PWM_CONTROL_SMOOTH_SHIFT(chan));
94 value |= 1 << PWM_CONTROL_TRIGGER_SHIFT(chan);
95 writel(value, kp->base + PWM_CONTROL_OFFSET);
96
97 /* Trigger bit must be held high for at least 400 ns. */
98 ndelay(400);
99 }
100
kona_pwmc_config(struct pwm_chip * chip,struct pwm_device * pwm,u64 duty_ns,u64 period_ns)101 static int kona_pwmc_config(struct pwm_chip *chip, struct pwm_device *pwm,
102 u64 duty_ns, u64 period_ns)
103 {
104 struct kona_pwmc *kp = to_kona_pwmc(chip);
105 u64 div, rate;
106 unsigned long prescale = PRESCALE_MIN, pc, dc;
107 unsigned int value, chan = pwm->hwpwm;
108
109 /*
110 * Find period count, duty count and prescale to suit duty_ns and
111 * period_ns. This is done according to formulas described below:
112 *
113 * period_ns = 10^9 * (PRESCALE + 1) * PC / PWM_CLK_RATE
114 * duty_ns = 10^9 * (PRESCALE + 1) * DC / PWM_CLK_RATE
115 *
116 * PC = (PWM_CLK_RATE * period_ns) / (10^9 * (PRESCALE + 1))
117 * DC = (PWM_CLK_RATE * duty_ns) / (10^9 * (PRESCALE + 1))
118 */
119
120 rate = clk_get_rate(kp->clk);
121
122 while (1) {
123 div = 1000000000;
124 div *= 1 + prescale;
125 pc = mul_u64_u64_div_u64(rate, period_ns, div);
126 dc = mul_u64_u64_div_u64(rate, duty_ns, div);
127
128 /* If duty_ns or period_ns are not achievable then return */
129 if (pc < PERIOD_COUNT_MIN)
130 return -EINVAL;
131
132 /* If pc and dc are in bounds, the calculation is done */
133 if (pc <= PERIOD_COUNT_MAX && dc <= DUTY_CYCLE_HIGH_MAX)
134 break;
135
136 /* Otherwise, increase prescale and recalculate pc and dc */
137 if (++prescale > PRESCALE_MAX)
138 return -EINVAL;
139 }
140
141 kona_pwmc_prepare_for_settings(kp, chan);
142
143 value = readl(kp->base + PRESCALE_OFFSET);
144 value &= ~PRESCALE_MASK(chan);
145 value |= prescale << PRESCALE_SHIFT(chan);
146 writel(value, kp->base + PRESCALE_OFFSET);
147
148 writel(pc, kp->base + PERIOD_COUNT_OFFSET(chan));
149
150 writel(dc, kp->base + DUTY_CYCLE_HIGH_OFFSET(chan));
151
152 kona_pwmc_apply_settings(kp, chan);
153
154 return 0;
155 }
156
kona_pwmc_set_polarity(struct pwm_chip * chip,struct pwm_device * pwm,enum pwm_polarity polarity)157 static int kona_pwmc_set_polarity(struct pwm_chip *chip, struct pwm_device *pwm,
158 enum pwm_polarity polarity)
159 {
160 struct kona_pwmc *kp = to_kona_pwmc(chip);
161 unsigned int chan = pwm->hwpwm;
162 unsigned int value;
163 int ret;
164
165 ret = clk_prepare_enable(kp->clk);
166 if (ret < 0) {
167 dev_err(chip->dev, "failed to enable clock: %d\n", ret);
168 return ret;
169 }
170
171 kona_pwmc_prepare_for_settings(kp, chan);
172
173 value = readl(kp->base + PWM_CONTROL_OFFSET);
174
175 if (polarity == PWM_POLARITY_NORMAL)
176 value |= 1 << PWM_CONTROL_POLARITY_SHIFT(chan);
177 else
178 value &= ~(1 << PWM_CONTROL_POLARITY_SHIFT(chan));
179
180 writel(value, kp->base + PWM_CONTROL_OFFSET);
181
182 kona_pwmc_apply_settings(kp, chan);
183
184 clk_disable_unprepare(kp->clk);
185
186 return 0;
187 }
188
kona_pwmc_enable(struct pwm_chip * chip,struct pwm_device * pwm)189 static int kona_pwmc_enable(struct pwm_chip *chip, struct pwm_device *pwm)
190 {
191 struct kona_pwmc *kp = to_kona_pwmc(chip);
192 int ret;
193
194 ret = clk_prepare_enable(kp->clk);
195 if (ret < 0) {
196 dev_err(chip->dev, "failed to enable clock: %d\n", ret);
197 return ret;
198 }
199
200 return 0;
201 }
202
kona_pwmc_disable(struct pwm_chip * chip,struct pwm_device * pwm)203 static void kona_pwmc_disable(struct pwm_chip *chip, struct pwm_device *pwm)
204 {
205 struct kona_pwmc *kp = to_kona_pwmc(chip);
206 unsigned int chan = pwm->hwpwm;
207 unsigned int value;
208
209 kona_pwmc_prepare_for_settings(kp, chan);
210
211 /* Simulate a disable by configuring for zero duty */
212 writel(0, kp->base + DUTY_CYCLE_HIGH_OFFSET(chan));
213 writel(0, kp->base + PERIOD_COUNT_OFFSET(chan));
214
215 /* Set prescale to 0 for this channel */
216 value = readl(kp->base + PRESCALE_OFFSET);
217 value &= ~PRESCALE_MASK(chan);
218 writel(value, kp->base + PRESCALE_OFFSET);
219
220 kona_pwmc_apply_settings(kp, chan);
221
222 clk_disable_unprepare(kp->clk);
223 }
224
kona_pwmc_apply(struct pwm_chip * chip,struct pwm_device * pwm,const struct pwm_state * state)225 static int kona_pwmc_apply(struct pwm_chip *chip, struct pwm_device *pwm,
226 const struct pwm_state *state)
227 {
228 int err;
229 struct kona_pwmc *kp = to_kona_pwmc(chip);
230 bool enabled = pwm->state.enabled;
231
232 if (state->polarity != pwm->state.polarity) {
233 if (enabled) {
234 kona_pwmc_disable(chip, pwm);
235 enabled = false;
236 }
237
238 err = kona_pwmc_set_polarity(chip, pwm, state->polarity);
239 if (err)
240 return err;
241
242 pwm->state.polarity = state->polarity;
243 }
244
245 if (!state->enabled) {
246 if (enabled)
247 kona_pwmc_disable(chip, pwm);
248 return 0;
249 } else if (!enabled) {
250 /*
251 * This is a bit special here, usually the PWM should only be
252 * enabled when duty and period are setup. But before this
253 * driver was converted to .apply it was done the other way
254 * around and so this behaviour was kept even though this might
255 * result in a glitch. This might be improvable by someone with
256 * hardware and/or documentation.
257 */
258 err = kona_pwmc_enable(chip, pwm);
259 if (err)
260 return err;
261 }
262
263 err = kona_pwmc_config(pwm->chip, pwm, state->duty_cycle, state->period);
264 if (err && !pwm->state.enabled)
265 clk_disable_unprepare(kp->clk);
266
267 return err;
268 }
269
270 static const struct pwm_ops kona_pwm_ops = {
271 .apply = kona_pwmc_apply,
272 .owner = THIS_MODULE,
273 };
274
kona_pwmc_probe(struct platform_device * pdev)275 static int kona_pwmc_probe(struct platform_device *pdev)
276 {
277 struct kona_pwmc *kp;
278 unsigned int chan;
279 unsigned int value = 0;
280 int ret = 0;
281
282 kp = devm_kzalloc(&pdev->dev, sizeof(*kp), GFP_KERNEL);
283 if (kp == NULL)
284 return -ENOMEM;
285
286 kp->chip.dev = &pdev->dev;
287 kp->chip.ops = &kona_pwm_ops;
288 kp->chip.npwm = 6;
289
290 kp->base = devm_platform_ioremap_resource(pdev, 0);
291 if (IS_ERR(kp->base))
292 return PTR_ERR(kp->base);
293
294 kp->clk = devm_clk_get(&pdev->dev, NULL);
295 if (IS_ERR(kp->clk)) {
296 dev_err(&pdev->dev, "failed to get clock: %ld\n",
297 PTR_ERR(kp->clk));
298 return PTR_ERR(kp->clk);
299 }
300
301 ret = clk_prepare_enable(kp->clk);
302 if (ret < 0) {
303 dev_err(&pdev->dev, "failed to enable clock: %d\n", ret);
304 return ret;
305 }
306
307 /* Set push/pull for all channels */
308 for (chan = 0; chan < kp->chip.npwm; chan++)
309 value |= (1 << PWM_CONTROL_TYPE_SHIFT(chan));
310
311 writel(value, kp->base + PWM_CONTROL_OFFSET);
312
313 clk_disable_unprepare(kp->clk);
314
315 ret = devm_pwmchip_add(&pdev->dev, &kp->chip);
316 if (ret < 0)
317 dev_err(&pdev->dev, "failed to add PWM chip: %d\n", ret);
318
319 return ret;
320 }
321
322 static const struct of_device_id bcm_kona_pwmc_dt[] = {
323 { .compatible = "brcm,kona-pwm" },
324 { },
325 };
326 MODULE_DEVICE_TABLE(of, bcm_kona_pwmc_dt);
327
328 static struct platform_driver kona_pwmc_driver = {
329 .driver = {
330 .name = "bcm-kona-pwm",
331 .of_match_table = bcm_kona_pwmc_dt,
332 },
333 .probe = kona_pwmc_probe,
334 };
335 module_platform_driver(kona_pwmc_driver);
336
337 MODULE_AUTHOR("Broadcom Corporation <bcm-kernel-feedback-list@broadcom.com>");
338 MODULE_AUTHOR("Tim Kryger <tkryger@broadcom.com>");
339 MODULE_DESCRIPTION("Broadcom Kona PWM driver");
340 MODULE_LICENSE("GPL v2");
341