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 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 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 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 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 } 108 109 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 } 129 130 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 } 148 149 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 }; 216 217 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 } 229 230 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 int ret; 236 237 ddata = devm_kzalloc(dev, sizeof(*ddata), GFP_KERNEL); 238 if (!ddata) 239 return -ENOMEM; 240 241 mutex_init(&ddata->lock); 242 chip = &ddata->chip; 243 chip->dev = dev; 244 chip->ops = &pwm_sifive_ops; 245 chip->npwm = 4; 246 247 ddata->regs = devm_platform_ioremap_resource(pdev, 0); 248 if (IS_ERR(ddata->regs)) 249 return PTR_ERR(ddata->regs); 250 251 ddata->clk = devm_clk_get(dev, NULL); 252 if (IS_ERR(ddata->clk)) 253 return dev_err_probe(dev, PTR_ERR(ddata->clk), 254 "Unable to find controller clock\n"); 255 256 ret = clk_prepare_enable(ddata->clk); 257 if (ret) { 258 dev_err(dev, "failed to enable clock for pwm: %d\n", ret); 259 return ret; 260 } 261 262 /* Watch for changes to underlying clock frequency */ 263 ddata->notifier.notifier_call = pwm_sifive_clock_notifier; 264 ret = clk_notifier_register(ddata->clk, &ddata->notifier); 265 if (ret) { 266 dev_err(dev, "failed to register clock notifier: %d\n", ret); 267 goto disable_clk; 268 } 269 270 ret = pwmchip_add(chip); 271 if (ret < 0) { 272 dev_err(dev, "cannot register PWM: %d\n", ret); 273 goto unregister_clk; 274 } 275 276 platform_set_drvdata(pdev, ddata); 277 dev_dbg(dev, "SiFive PWM chip registered %d PWMs\n", chip->npwm); 278 279 return 0; 280 281 unregister_clk: 282 clk_notifier_unregister(ddata->clk, &ddata->notifier); 283 disable_clk: 284 clk_disable_unprepare(ddata->clk); 285 286 return ret; 287 } 288 289 static int pwm_sifive_remove(struct platform_device *dev) 290 { 291 struct pwm_sifive_ddata *ddata = platform_get_drvdata(dev); 292 bool is_enabled = false; 293 struct pwm_device *pwm; 294 int ch; 295 296 for (ch = 0; ch < ddata->chip.npwm; ch++) { 297 pwm = &ddata->chip.pwms[ch]; 298 if (pwm->state.enabled) { 299 is_enabled = true; 300 break; 301 } 302 } 303 if (is_enabled) 304 clk_disable(ddata->clk); 305 306 clk_disable_unprepare(ddata->clk); 307 pwmchip_remove(&ddata->chip); 308 clk_notifier_unregister(ddata->clk, &ddata->notifier); 309 310 return 0; 311 } 312 313 static const struct of_device_id pwm_sifive_of_match[] = { 314 { .compatible = "sifive,pwm0" }, 315 {}, 316 }; 317 MODULE_DEVICE_TABLE(of, pwm_sifive_of_match); 318 319 static struct platform_driver pwm_sifive_driver = { 320 .probe = pwm_sifive_probe, 321 .remove = pwm_sifive_remove, 322 .driver = { 323 .name = "pwm-sifive", 324 .of_match_table = pwm_sifive_of_match, 325 }, 326 }; 327 module_platform_driver(pwm_sifive_driver); 328 329 MODULE_DESCRIPTION("SiFive PWM driver"); 330 MODULE_LICENSE("GPL v2"); 331