1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * STM32 Low-Power Timer PWM driver 4 * 5 * Copyright (C) STMicroelectronics 2017 6 * 7 * Author: Gerald Baeza <gerald.baeza@st.com> 8 * 9 * Inspired by Gerald Baeza's pwm-stm32 driver 10 */ 11 12 #include <linux/bitfield.h> 13 #include <linux/mfd/stm32-lptimer.h> 14 #include <linux/module.h> 15 #include <linux/of.h> 16 #include <linux/pinctrl/consumer.h> 17 #include <linux/platform_device.h> 18 #include <linux/pwm.h> 19 20 struct stm32_pwm_lp { 21 struct pwm_chip chip; 22 struct clk *clk; 23 struct regmap *regmap; 24 }; 25 26 static inline struct stm32_pwm_lp *to_stm32_pwm_lp(struct pwm_chip *chip) 27 { 28 return container_of(chip, struct stm32_pwm_lp, chip); 29 } 30 31 /* STM32 Low-Power Timer is preceded by a configurable power-of-2 prescaler */ 32 #define STM32_LPTIM_MAX_PRESCALER 128 33 34 static int stm32_pwm_lp_apply(struct pwm_chip *chip, struct pwm_device *pwm, 35 const struct pwm_state *state) 36 { 37 struct stm32_pwm_lp *priv = to_stm32_pwm_lp(chip); 38 unsigned long long prd, div, dty; 39 struct pwm_state cstate; 40 u32 val, mask, cfgr, presc = 0; 41 bool reenable; 42 int ret; 43 44 pwm_get_state(pwm, &cstate); 45 reenable = !cstate.enabled; 46 47 if (!state->enabled) { 48 if (cstate.enabled) { 49 /* Disable LP timer */ 50 ret = regmap_write(priv->regmap, STM32_LPTIM_CR, 0); 51 if (ret) 52 return ret; 53 /* disable clock to PWM counter */ 54 clk_disable(priv->clk); 55 } 56 return 0; 57 } 58 59 /* Calculate the period and prescaler value */ 60 div = (unsigned long long)clk_get_rate(priv->clk) * state->period; 61 do_div(div, NSEC_PER_SEC); 62 if (!div) { 63 /* Clock is too slow to achieve requested period. */ 64 dev_dbg(priv->chip.dev, "Can't reach %llu ns\n", state->period); 65 return -EINVAL; 66 } 67 68 prd = div; 69 while (div > STM32_LPTIM_MAX_ARR) { 70 presc++; 71 if ((1 << presc) > STM32_LPTIM_MAX_PRESCALER) { 72 dev_err(priv->chip.dev, "max prescaler exceeded\n"); 73 return -EINVAL; 74 } 75 div = prd >> presc; 76 } 77 prd = div; 78 79 /* Calculate the duty cycle */ 80 dty = prd * state->duty_cycle; 81 do_div(dty, state->period); 82 83 if (!cstate.enabled) { 84 /* enable clock to drive PWM counter */ 85 ret = clk_enable(priv->clk); 86 if (ret) 87 return ret; 88 } 89 90 ret = regmap_read(priv->regmap, STM32_LPTIM_CFGR, &cfgr); 91 if (ret) 92 goto err; 93 94 if ((FIELD_GET(STM32_LPTIM_PRESC, cfgr) != presc) || 95 (FIELD_GET(STM32_LPTIM_WAVPOL, cfgr) != state->polarity)) { 96 val = FIELD_PREP(STM32_LPTIM_PRESC, presc); 97 val |= FIELD_PREP(STM32_LPTIM_WAVPOL, state->polarity); 98 mask = STM32_LPTIM_PRESC | STM32_LPTIM_WAVPOL; 99 100 /* Must disable LP timer to modify CFGR */ 101 reenable = true; 102 ret = regmap_write(priv->regmap, STM32_LPTIM_CR, 0); 103 if (ret) 104 goto err; 105 106 ret = regmap_update_bits(priv->regmap, STM32_LPTIM_CFGR, mask, 107 val); 108 if (ret) 109 goto err; 110 } 111 112 if (reenable) { 113 /* Must (re)enable LP timer to modify CMP & ARR */ 114 ret = regmap_write(priv->regmap, STM32_LPTIM_CR, 115 STM32_LPTIM_ENABLE); 116 if (ret) 117 goto err; 118 } 119 120 ret = regmap_write(priv->regmap, STM32_LPTIM_ARR, prd - 1); 121 if (ret) 122 goto err; 123 124 ret = regmap_write(priv->regmap, STM32_LPTIM_CMP, prd - (1 + dty)); 125 if (ret) 126 goto err; 127 128 /* ensure CMP & ARR registers are properly written */ 129 ret = regmap_read_poll_timeout(priv->regmap, STM32_LPTIM_ISR, val, 130 (val & STM32_LPTIM_CMPOK_ARROK), 131 100, 1000); 132 if (ret) { 133 dev_err(priv->chip.dev, "ARR/CMP registers write issue\n"); 134 goto err; 135 } 136 ret = regmap_write(priv->regmap, STM32_LPTIM_ICR, 137 STM32_LPTIM_CMPOKCF_ARROKCF); 138 if (ret) 139 goto err; 140 141 if (reenable) { 142 /* Start LP timer in continuous mode */ 143 ret = regmap_set_bits(priv->regmap, STM32_LPTIM_CR, 144 STM32_LPTIM_CNTSTRT); 145 if (ret) { 146 regmap_write(priv->regmap, STM32_LPTIM_CR, 0); 147 goto err; 148 } 149 } 150 151 return 0; 152 err: 153 if (!cstate.enabled) 154 clk_disable(priv->clk); 155 156 return ret; 157 } 158 159 static int stm32_pwm_lp_get_state(struct pwm_chip *chip, 160 struct pwm_device *pwm, 161 struct pwm_state *state) 162 { 163 struct stm32_pwm_lp *priv = to_stm32_pwm_lp(chip); 164 unsigned long rate = clk_get_rate(priv->clk); 165 u32 val, presc, prd; 166 u64 tmp; 167 168 regmap_read(priv->regmap, STM32_LPTIM_CR, &val); 169 state->enabled = !!FIELD_GET(STM32_LPTIM_ENABLE, val); 170 /* Keep PWM counter clock refcount in sync with PWM initial state */ 171 if (state->enabled) 172 clk_enable(priv->clk); 173 174 regmap_read(priv->regmap, STM32_LPTIM_CFGR, &val); 175 presc = FIELD_GET(STM32_LPTIM_PRESC, val); 176 state->polarity = FIELD_GET(STM32_LPTIM_WAVPOL, val); 177 178 regmap_read(priv->regmap, STM32_LPTIM_ARR, &prd); 179 tmp = prd + 1; 180 tmp = (tmp << presc) * NSEC_PER_SEC; 181 state->period = DIV_ROUND_CLOSEST_ULL(tmp, rate); 182 183 regmap_read(priv->regmap, STM32_LPTIM_CMP, &val); 184 tmp = prd - val; 185 tmp = (tmp << presc) * NSEC_PER_SEC; 186 state->duty_cycle = DIV_ROUND_CLOSEST_ULL(tmp, rate); 187 188 return 0; 189 } 190 191 static const struct pwm_ops stm32_pwm_lp_ops = { 192 .owner = THIS_MODULE, 193 .apply = stm32_pwm_lp_apply, 194 .get_state = stm32_pwm_lp_get_state, 195 }; 196 197 static int stm32_pwm_lp_probe(struct platform_device *pdev) 198 { 199 struct stm32_lptimer *ddata = dev_get_drvdata(pdev->dev.parent); 200 struct stm32_pwm_lp *priv; 201 int ret; 202 203 priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL); 204 if (!priv) 205 return -ENOMEM; 206 207 priv->regmap = ddata->regmap; 208 priv->clk = ddata->clk; 209 priv->chip.dev = &pdev->dev; 210 priv->chip.ops = &stm32_pwm_lp_ops; 211 priv->chip.npwm = 1; 212 213 ret = devm_pwmchip_add(&pdev->dev, &priv->chip); 214 if (ret < 0) 215 return ret; 216 217 platform_set_drvdata(pdev, priv); 218 219 return 0; 220 } 221 222 static int __maybe_unused stm32_pwm_lp_suspend(struct device *dev) 223 { 224 struct stm32_pwm_lp *priv = dev_get_drvdata(dev); 225 struct pwm_state state; 226 227 pwm_get_state(&priv->chip.pwms[0], &state); 228 if (state.enabled) { 229 dev_err(dev, "The consumer didn't stop us (%s)\n", 230 priv->chip.pwms[0].label); 231 return -EBUSY; 232 } 233 234 return pinctrl_pm_select_sleep_state(dev); 235 } 236 237 static int __maybe_unused stm32_pwm_lp_resume(struct device *dev) 238 { 239 return pinctrl_pm_select_default_state(dev); 240 } 241 242 static SIMPLE_DEV_PM_OPS(stm32_pwm_lp_pm_ops, stm32_pwm_lp_suspend, 243 stm32_pwm_lp_resume); 244 245 static const struct of_device_id stm32_pwm_lp_of_match[] = { 246 { .compatible = "st,stm32-pwm-lp", }, 247 {}, 248 }; 249 MODULE_DEVICE_TABLE(of, stm32_pwm_lp_of_match); 250 251 static struct platform_driver stm32_pwm_lp_driver = { 252 .probe = stm32_pwm_lp_probe, 253 .driver = { 254 .name = "stm32-pwm-lp", 255 .of_match_table = of_match_ptr(stm32_pwm_lp_of_match), 256 .pm = &stm32_pwm_lp_pm_ops, 257 }, 258 }; 259 module_platform_driver(stm32_pwm_lp_driver); 260 261 MODULE_ALIAS("platform:stm32-pwm-lp"); 262 MODULE_DESCRIPTION("STMicroelectronics STM32 PWM LP driver"); 263 MODULE_LICENSE("GPL v2"); 264