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/module.h>
17 #include <linux/platform_device.h>
18 #include <linux/pwm.h>
19 #include <linux/slab.h>
20 #include <linux/bitfield.h>
21
22 /* Register offsets */
23 #define PWM_SIFIVE_PWMCFG 0x0
24 #define PWM_SIFIVE_PWMCOUNT 0x8
25 #define PWM_SIFIVE_PWMS 0x10
26 #define PWM_SIFIVE_PWMCMP0 0x20
27
28 /* PWMCFG fields */
29 #define PWM_SIFIVE_PWMCFG_SCALE GENMASK(3, 0)
30 #define PWM_SIFIVE_PWMCFG_STICKY BIT(8)
31 #define PWM_SIFIVE_PWMCFG_ZERO_CMP BIT(9)
32 #define PWM_SIFIVE_PWMCFG_DEGLITCH BIT(10)
33 #define PWM_SIFIVE_PWMCFG_EN_ALWAYS BIT(12)
34 #define PWM_SIFIVE_PWMCFG_EN_ONCE BIT(13)
35 #define PWM_SIFIVE_PWMCFG_CENTER BIT(16)
36 #define PWM_SIFIVE_PWMCFG_GANG BIT(24)
37 #define PWM_SIFIVE_PWMCFG_IP BIT(28)
38
39 /* PWM_SIFIVE_SIZE_PWMCMP is used to calculate offset for pwmcmpX registers */
40 #define PWM_SIFIVE_SIZE_PWMCMP 4
41 #define PWM_SIFIVE_CMPWIDTH 16
42 #define PWM_SIFIVE_DEFAULT_PERIOD 10000000
43
44 struct pwm_sifive_ddata {
45 struct pwm_chip chip;
46 struct mutex lock; /* lock to protect user_count */
47 struct notifier_block notifier;
48 struct clk *clk;
49 void __iomem *regs;
50 unsigned int real_period;
51 unsigned int approx_period;
52 int user_count;
53 };
54
55 static inline
pwm_sifive_chip_to_ddata(struct pwm_chip * c)56 struct pwm_sifive_ddata *pwm_sifive_chip_to_ddata(struct pwm_chip *c)
57 {
58 return container_of(c, struct pwm_sifive_ddata, chip);
59 }
60
pwm_sifive_request(struct pwm_chip * chip,struct pwm_device * pwm)61 static int pwm_sifive_request(struct pwm_chip *chip, struct pwm_device *pwm)
62 {
63 struct pwm_sifive_ddata *ddata = pwm_sifive_chip_to_ddata(chip);
64
65 mutex_lock(&ddata->lock);
66 ddata->user_count++;
67 mutex_unlock(&ddata->lock);
68
69 return 0;
70 }
71
pwm_sifive_free(struct pwm_chip * chip,struct pwm_device * pwm)72 static void pwm_sifive_free(struct pwm_chip *chip, struct pwm_device *pwm)
73 {
74 struct pwm_sifive_ddata *ddata = pwm_sifive_chip_to_ddata(chip);
75
76 mutex_lock(&ddata->lock);
77 ddata->user_count--;
78 mutex_unlock(&ddata->lock);
79 }
80
pwm_sifive_update_clock(struct pwm_sifive_ddata * ddata,unsigned long rate)81 static 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
pwm_sifive_get_state(struct pwm_chip * chip,struct pwm_device * pwm,struct pwm_state * state)109 static void 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_PWMCMP0 +
116 pwm->hwpwm * PWM_SIFIVE_SIZE_PWMCMP);
117
118 state->enabled = duty > 0;
119
120 val = readl(ddata->regs + PWM_SIFIVE_PWMCFG);
121 if (!(val & PWM_SIFIVE_PWMCFG_EN_ALWAYS))
122 state->enabled = false;
123
124 state->period = ddata->real_period;
125 state->duty_cycle =
126 (u64)duty * ddata->real_period >> PWM_SIFIVE_CMPWIDTH;
127 state->polarity = PWM_POLARITY_INVERSED;
128 }
129
pwm_sifive_enable(struct pwm_chip * chip,bool enable)130 static int pwm_sifive_enable(struct pwm_chip *chip, bool enable)
131 {
132 struct pwm_sifive_ddata *ddata = pwm_sifive_chip_to_ddata(chip);
133 int ret;
134
135 if (enable) {
136 ret = clk_enable(ddata->clk);
137 if (ret) {
138 dev_err(ddata->chip.dev, "Enable clk failed\n");
139 return ret;
140 }
141 }
142
143 if (!enable)
144 clk_disable(ddata->clk);
145
146 return 0;
147 }
148
pwm_sifive_apply(struct pwm_chip * chip,struct pwm_device * pwm,const struct pwm_state * state)149 static int pwm_sifive_apply(struct pwm_chip *chip, struct pwm_device *pwm,
150 const struct pwm_state *state)
151 {
152 struct pwm_sifive_ddata *ddata = pwm_sifive_chip_to_ddata(chip);
153 struct pwm_state cur_state;
154 unsigned int duty_cycle;
155 unsigned long long num;
156 bool enabled;
157 int ret = 0;
158 u32 frac;
159
160 if (state->polarity != PWM_POLARITY_INVERSED)
161 return -EINVAL;
162
163 ret = clk_enable(ddata->clk);
164 if (ret) {
165 dev_err(ddata->chip.dev, "Enable clk failed\n");
166 return ret;
167 }
168
169 mutex_lock(&ddata->lock);
170 cur_state = pwm->state;
171 enabled = cur_state.enabled;
172
173 duty_cycle = state->duty_cycle;
174 if (!state->enabled)
175 duty_cycle = 0;
176
177 /*
178 * The problem of output producing mixed setting as mentioned at top,
179 * occurs here. To minimize the window for this problem, we are
180 * calculating the register values first and then writing them
181 * consecutively
182 */
183 num = (u64)duty_cycle * (1U << PWM_SIFIVE_CMPWIDTH);
184 frac = DIV64_U64_ROUND_CLOSEST(num, state->period);
185 /* The hardware cannot generate a 100% duty cycle */
186 frac = min(frac, (1U << PWM_SIFIVE_CMPWIDTH) - 1);
187
188 if (state->period != ddata->approx_period) {
189 if (ddata->user_count != 1) {
190 ret = -EBUSY;
191 goto exit;
192 }
193 ddata->approx_period = state->period;
194 pwm_sifive_update_clock(ddata, clk_get_rate(ddata->clk));
195 }
196
197 writel(frac, ddata->regs + PWM_SIFIVE_PWMCMP0 +
198 pwm->hwpwm * PWM_SIFIVE_SIZE_PWMCMP);
199
200 if (state->enabled != enabled)
201 pwm_sifive_enable(chip, state->enabled);
202
203 exit:
204 clk_disable(ddata->clk);
205 mutex_unlock(&ddata->lock);
206 return ret;
207 }
208
209 static const struct pwm_ops pwm_sifive_ops = {
210 .request = pwm_sifive_request,
211 .free = pwm_sifive_free,
212 .get_state = pwm_sifive_get_state,
213 .apply = pwm_sifive_apply,
214 .owner = THIS_MODULE,
215 };
216
pwm_sifive_clock_notifier(struct notifier_block * nb,unsigned long event,void * data)217 static int pwm_sifive_clock_notifier(struct notifier_block *nb,
218 unsigned long event, void *data)
219 {
220 struct clk_notifier_data *ndata = data;
221 struct pwm_sifive_ddata *ddata =
222 container_of(nb, struct pwm_sifive_ddata, notifier);
223
224 if (event == POST_RATE_CHANGE)
225 pwm_sifive_update_clock(ddata, ndata->new_rate);
226
227 return NOTIFY_OK;
228 }
229
pwm_sifive_probe(struct platform_device * pdev)230 static int pwm_sifive_probe(struct platform_device *pdev)
231 {
232 struct device *dev = &pdev->dev;
233 struct pwm_sifive_ddata *ddata;
234 struct pwm_chip *chip;
235 struct resource *res;
236 int ret;
237
238 ddata = devm_kzalloc(dev, sizeof(*ddata), GFP_KERNEL);
239 if (!ddata)
240 return -ENOMEM;
241
242 mutex_init(&ddata->lock);
243 chip = &ddata->chip;
244 chip->dev = dev;
245 chip->ops = &pwm_sifive_ops;
246 chip->of_xlate = of_pwm_xlate_with_flags;
247 chip->of_pwm_n_cells = 3;
248 chip->base = -1;
249 chip->npwm = 4;
250
251 res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
252 ddata->regs = devm_ioremap_resource(dev, res);
253 if (IS_ERR(ddata->regs))
254 return PTR_ERR(ddata->regs);
255
256 ddata->clk = devm_clk_get(dev, NULL);
257 if (IS_ERR(ddata->clk))
258 return dev_err_probe(dev, PTR_ERR(ddata->clk),
259 "Unable to find controller clock\n");
260
261 ret = clk_prepare_enable(ddata->clk);
262 if (ret) {
263 dev_err(dev, "failed to enable clock for pwm: %d\n", ret);
264 return ret;
265 }
266
267 /* Watch for changes to underlying clock frequency */
268 ddata->notifier.notifier_call = pwm_sifive_clock_notifier;
269 ret = clk_notifier_register(ddata->clk, &ddata->notifier);
270 if (ret) {
271 dev_err(dev, "failed to register clock notifier: %d\n", ret);
272 goto disable_clk;
273 }
274
275 ret = pwmchip_add(chip);
276 if (ret < 0) {
277 dev_err(dev, "cannot register PWM: %d\n", ret);
278 goto unregister_clk;
279 }
280
281 platform_set_drvdata(pdev, ddata);
282 dev_dbg(dev, "SiFive PWM chip registered %d PWMs\n", chip->npwm);
283
284 return 0;
285
286 unregister_clk:
287 clk_notifier_unregister(ddata->clk, &ddata->notifier);
288 disable_clk:
289 clk_disable_unprepare(ddata->clk);
290
291 return ret;
292 }
293
pwm_sifive_remove(struct platform_device * dev)294 static int pwm_sifive_remove(struct platform_device *dev)
295 {
296 struct pwm_sifive_ddata *ddata = platform_get_drvdata(dev);
297 bool is_enabled = false;
298 struct pwm_device *pwm;
299 int ret, ch;
300
301 for (ch = 0; ch < ddata->chip.npwm; ch++) {
302 pwm = &ddata->chip.pwms[ch];
303 if (pwm->state.enabled) {
304 is_enabled = true;
305 break;
306 }
307 }
308 if (is_enabled)
309 clk_disable(ddata->clk);
310
311 clk_disable_unprepare(ddata->clk);
312 ret = pwmchip_remove(&ddata->chip);
313 clk_notifier_unregister(ddata->clk, &ddata->notifier);
314
315 return ret;
316 }
317
318 static const struct of_device_id pwm_sifive_of_match[] = {
319 { .compatible = "sifive,pwm0" },
320 {},
321 };
322 MODULE_DEVICE_TABLE(of, pwm_sifive_of_match);
323
324 static struct platform_driver pwm_sifive_driver = {
325 .probe = pwm_sifive_probe,
326 .remove = pwm_sifive_remove,
327 .driver = {
328 .name = "pwm-sifive",
329 .of_match_table = pwm_sifive_of_match,
330 },
331 };
332 module_platform_driver(pwm_sifive_driver);
333
334 MODULE_DESCRIPTION("SiFive PWM driver");
335 MODULE_LICENSE("GPL v2");
336
