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