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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Copyright (C) 2017-2018 SiFive
4 * For SiFive's PWM IP block documentation please refer Chapter 14 of
5 * Reference Manual : https://static.dev.sifive.com/FU540-C000-v1.0.pdf
6 *
7 * Limitations:
8 * - When changing both duty cycle and period, we cannot prevent in
9 * software that the output might produce a period with mixed
10 * settings (new period length and old duty cycle).
11 * - The hardware cannot generate a 100% duty cycle.
12 * - The hardware generates only inverted output.
13 */
14#include <linux/clk.h>
15#include <linux/io.h>
16#include <linux/mod_devicetable.h>
17#include <linux/module.h>
18#include <linux/platform_device.h>
19#include <linux/pwm.h>
20#include <linux/slab.h>
21#include <linux/bitfield.h>
22
23/* Register offsets */
24#define PWM_SIFIVE_PWMCFG 0x0
25#define PWM_SIFIVE_PWMCOUNT 0x8
26#define PWM_SIFIVE_PWMS 0x10
27#define PWM_SIFIVE_PWMCMP(i) (0x20 + 4 * (i))
28
29/* PWMCFG fields */
30#define PWM_SIFIVE_PWMCFG_SCALE GENMASK(3, 0)
31#define PWM_SIFIVE_PWMCFG_STICKY BIT(8)
32#define PWM_SIFIVE_PWMCFG_ZERO_CMP BIT(9)
33#define PWM_SIFIVE_PWMCFG_DEGLITCH BIT(10)
34#define PWM_SIFIVE_PWMCFG_EN_ALWAYS BIT(12)
35#define PWM_SIFIVE_PWMCFG_EN_ONCE BIT(13)
36#define PWM_SIFIVE_PWMCFG_CENTER BIT(16)
37#define PWM_SIFIVE_PWMCFG_GANG BIT(24)
38#define PWM_SIFIVE_PWMCFG_IP BIT(28)
39
40#define PWM_SIFIVE_CMPWIDTH 16
41#define PWM_SIFIVE_DEFAULT_PERIOD 10000000
42
43struct pwm_sifive_ddata {
44 struct pwm_chip chip;
45 struct mutex lock; /* lock to protect user_count and approx_period */
46 struct notifier_block notifier;
47 struct clk *clk;
48 void __iomem *regs;
49 unsigned int real_period;
50 unsigned int approx_period;
51 int user_count;
52};
53
54static inline
55struct pwm_sifive_ddata *pwm_sifive_chip_to_ddata(struct pwm_chip *chip)
56{
57 return container_of(chip, struct pwm_sifive_ddata, chip);
58}
59
60static int pwm_sifive_request(struct pwm_chip *chip, struct pwm_device *pwm)
61{
62 struct pwm_sifive_ddata *ddata = pwm_sifive_chip_to_ddata(chip);
63
64 mutex_lock(&ddata->lock);
65 ddata->user_count++;
66 mutex_unlock(&ddata->lock);
67
68 return 0;
69}
70
71static void pwm_sifive_free(struct pwm_chip *chip, struct pwm_device *pwm)
72{
73 struct pwm_sifive_ddata *ddata = pwm_sifive_chip_to_ddata(chip);
74
75 mutex_lock(&ddata->lock);
76 ddata->user_count--;
77 mutex_unlock(&ddata->lock);
78}
79
80/* Called holding ddata->lock */
81static void pwm_sifive_update_clock(struct pwm_sifive_ddata *ddata,
82 unsigned long rate)
83{
84 unsigned long long num;
85 unsigned long scale_pow;
86 int scale;
87 u32 val;
88 /*
89 * The PWM unit is used with pwmzerocmp=0, so the only way to modify the
90 * period length is using pwmscale which provides the number of bits the
91 * counter is shifted before being feed to the comparators. A period
92 * lasts (1 << (PWM_SIFIVE_CMPWIDTH + pwmscale)) clock ticks.
93 * (1 << (PWM_SIFIVE_CMPWIDTH + scale)) * 10^9/rate = period
94 */
95 scale_pow = div64_ul(ddata->approx_period * (u64)rate, NSEC_PER_SEC);
96 scale = clamp(ilog2(scale_pow) - PWM_SIFIVE_CMPWIDTH, 0, 0xf);
97
98 val = PWM_SIFIVE_PWMCFG_EN_ALWAYS |
99 FIELD_PREP(PWM_SIFIVE_PWMCFG_SCALE, scale);
100 writel(val, ddata->regs + PWM_SIFIVE_PWMCFG);
101
102 /* As scale <= 15 the shift operation cannot overflow. */
103 num = (unsigned long long)NSEC_PER_SEC << (PWM_SIFIVE_CMPWIDTH + scale);
104 ddata->real_period = div64_ul(num, rate);
105 dev_dbg(ddata->chip.dev,
106 "New real_period = %u ns\n", ddata->real_period);
107}
108
109static int pwm_sifive_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
110 struct pwm_state *state)
111{
112 struct pwm_sifive_ddata *ddata = pwm_sifive_chip_to_ddata(chip);
113 u32 duty, val;
114
115 duty = readl(ddata->regs + PWM_SIFIVE_PWMCMP(pwm->hwpwm));
116
117 state->enabled = duty > 0;
118
119 val = readl(ddata->regs + PWM_SIFIVE_PWMCFG);
120 if (!(val & PWM_SIFIVE_PWMCFG_EN_ALWAYS))
121 state->enabled = false;
122
123 state->period = ddata->real_period;
124 state->duty_cycle =
125 (u64)duty * ddata->real_period >> PWM_SIFIVE_CMPWIDTH;
126 state->polarity = PWM_POLARITY_INVERSED;
127
128 return 0;
129}
130
131static int pwm_sifive_apply(struct pwm_chip *chip, struct pwm_device *pwm,
132 const struct pwm_state *state)
133{
134 struct pwm_sifive_ddata *ddata = pwm_sifive_chip_to_ddata(chip);
135 struct pwm_state cur_state;
136 unsigned int duty_cycle;
137 unsigned long long num;
138 bool enabled;
139 int ret = 0;
140 u32 frac;
141
142 if (state->polarity != PWM_POLARITY_INVERSED)
143 return -EINVAL;
144
145 cur_state = pwm->state;
146 enabled = cur_state.enabled;
147
148 duty_cycle = state->duty_cycle;
149 if (!state->enabled)
150 duty_cycle = 0;
151
152 /*
153 * The problem of output producing mixed setting as mentioned at top,
154 * occurs here. To minimize the window for this problem, we are
155 * calculating the register values first and then writing them
156 * consecutively
157 */
158 num = (u64)duty_cycle * (1U << PWM_SIFIVE_CMPWIDTH);
159 frac = DIV64_U64_ROUND_CLOSEST(num, state->period);
160 /* The hardware cannot generate a 100% duty cycle */
161 frac = min(frac, (1U << PWM_SIFIVE_CMPWIDTH) - 1);
162
163 mutex_lock(&ddata->lock);
164 if (state->period != ddata->approx_period) {
165 /*
166 * Don't let a 2nd user change the period underneath the 1st user.
167 * However if ddate->approx_period == 0 this is the first time we set
168 * any period, so let whoever gets here first set the period so other
169 * users who agree on the period won't fail.
170 */
171 if (ddata->user_count != 1 && ddata->approx_period) {
172 mutex_unlock(&ddata->lock);
173 return -EBUSY;
174 }
175 ddata->approx_period = state->period;
176 pwm_sifive_update_clock(ddata, clk_get_rate(ddata->clk));
177 }
178 mutex_unlock(&ddata->lock);
179
180 /*
181 * If the PWM is enabled the clk is already on. So only enable it
182 * conditionally to have it on exactly once afterwards independent of
183 * the PWM state.
184 */
185 if (!enabled) {
186 ret = clk_enable(ddata->clk);
187 if (ret) {
188 dev_err(ddata->chip.dev, "Enable clk failed\n");
189 return ret;
190 }
191 }
192
193 writel(frac, ddata->regs + PWM_SIFIVE_PWMCMP(pwm->hwpwm));
194
195 if (!state->enabled)
196 clk_disable(ddata->clk);
197
198 return 0;
199}
200
201static const struct pwm_ops pwm_sifive_ops = {
202 .request = pwm_sifive_request,
203 .free = pwm_sifive_free,
204 .get_state = pwm_sifive_get_state,
205 .apply = pwm_sifive_apply,
206};
207
208static int pwm_sifive_clock_notifier(struct notifier_block *nb,
209 unsigned long event, void *data)
210{
211 struct clk_notifier_data *ndata = data;
212 struct pwm_sifive_ddata *ddata =
213 container_of(nb, struct pwm_sifive_ddata, notifier);
214
215 if (event == POST_RATE_CHANGE) {
216 mutex_lock(&ddata->lock);
217 pwm_sifive_update_clock(ddata, ndata->new_rate);
218 mutex_unlock(&ddata->lock);
219 }
220
221 return NOTIFY_OK;
222}
223
224static int pwm_sifive_probe(struct platform_device *pdev)
225{
226 struct device *dev = &pdev->dev;
227 struct pwm_sifive_ddata *ddata;
228 struct pwm_chip *chip;
229 int ret;
230 u32 val;
231 unsigned int enabled_pwms = 0, enabled_clks = 1;
232
233 ddata = devm_kzalloc(dev, sizeof(*ddata), GFP_KERNEL);
234 if (!ddata)
235 return -ENOMEM;
236
237 mutex_init(&ddata->lock);
238 chip = &ddata->chip;
239 chip->dev = dev;
240 chip->ops = &pwm_sifive_ops;
241 chip->npwm = 4;
242
243 ddata->regs = devm_platform_ioremap_resource(pdev, 0);
244 if (IS_ERR(ddata->regs))
245 return PTR_ERR(ddata->regs);
246
247 ddata->clk = devm_clk_get_prepared(dev, NULL);
248 if (IS_ERR(ddata->clk))
249 return dev_err_probe(dev, PTR_ERR(ddata->clk),
250 "Unable to find controller clock\n");
251
252 ret = clk_enable(ddata->clk);
253 if (ret) {
254 dev_err(dev, "failed to enable clock for pwm: %d\n", ret);
255 return ret;
256 }
257
258 val = readl(ddata->regs + PWM_SIFIVE_PWMCFG);
259 if (val & PWM_SIFIVE_PWMCFG_EN_ALWAYS) {
260 unsigned int i;
261
262 for (i = 0; i < chip->npwm; ++i) {
263 val = readl(ddata->regs + PWM_SIFIVE_PWMCMP(i));
264 if (val > 0)
265 ++enabled_pwms;
266 }
267 }
268
269 /* The clk should be on once for each running PWM. */
270 if (enabled_pwms) {
271 while (enabled_clks < enabled_pwms) {
272 /* This is not expected to fail as the clk is already on */
273 ret = clk_enable(ddata->clk);
274 if (unlikely(ret)) {
275 dev_err_probe(dev, ret, "Failed to enable clk\n");
276 goto disable_clk;
277 }
278 ++enabled_clks;
279 }
280 } else {
281 clk_disable(ddata->clk);
282 enabled_clks = 0;
283 }
284
285 /* Watch for changes to underlying clock frequency */
286 ddata->notifier.notifier_call = pwm_sifive_clock_notifier;
287 ret = clk_notifier_register(ddata->clk, &ddata->notifier);
288 if (ret) {
289 dev_err(dev, "failed to register clock notifier: %d\n", ret);
290 goto disable_clk;
291 }
292
293 ret = pwmchip_add(chip);
294 if (ret < 0) {
295 dev_err(dev, "cannot register PWM: %d\n", ret);
296 goto unregister_clk;
297 }
298
299 platform_set_drvdata(pdev, ddata);
300 dev_dbg(dev, "SiFive PWM chip registered %d PWMs\n", chip->npwm);
301
302 return 0;
303
304unregister_clk:
305 clk_notifier_unregister(ddata->clk, &ddata->notifier);
306disable_clk:
307 while (enabled_clks) {
308 clk_disable(ddata->clk);
309 --enabled_clks;
310 }
311
312 return ret;
313}
314
315static void pwm_sifive_remove(struct platform_device *dev)
316{
317 struct pwm_sifive_ddata *ddata = platform_get_drvdata(dev);
318 struct pwm_device *pwm;
319 int ch;
320
321 pwmchip_remove(&ddata->chip);
322 clk_notifier_unregister(ddata->clk, &ddata->notifier);
323
324 for (ch = 0; ch < ddata->chip.npwm; ch++) {
325 pwm = &ddata->chip.pwms[ch];
326 if (pwm->state.enabled)
327 clk_disable(ddata->clk);
328 }
329}
330
331static const struct of_device_id pwm_sifive_of_match[] = {
332 { .compatible = "sifive,pwm0" },
333 {},
334};
335MODULE_DEVICE_TABLE(of, pwm_sifive_of_match);
336
337static struct platform_driver pwm_sifive_driver = {
338 .probe = pwm_sifive_probe,
339 .remove_new = pwm_sifive_remove,
340 .driver = {
341 .name = "pwm-sifive",
342 .of_match_table = pwm_sifive_of_match,
343 },
344};
345module_platform_driver(pwm_sifive_driver);
346
347MODULE_DESCRIPTION("SiFive PWM driver");
348MODULE_LICENSE("GPL v2");