drivers/pwm/pwm-stm32-lp.c

   1 /*
   2  * STM32 Low-Power Timer PWM driver
   3  *
   4  * Copyright (C) STMicroelectronics 2017
   5  *
   6  * Author: Gerald Baeza <gerald.baeza@st.com>
   7  *
   8  * License terms: GNU General Public License (GPL), version 2
   9  *
  10  * Inspired by Gerald Baeza's pwm-stm32 driver
  11  */
  12
  13 #include <linux/bitfield.h>
  14 #include <linux/mfd/stm32-lptimer.h>
  15 #include <linux/module.h>
  16 #include <linux/of.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                               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 %u 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_update_bits(priv->regmap, STM32_LPTIM_CR,
 144                                          STM32_LPTIM_CNTSTRT,
 145                                          STM32_LPTIM_CNTSTRT);
 146                 if (ret) {
 147                         regmap_write(priv->regmap, STM32_LPTIM_CR, 0);
 148                         goto err;
 149                 }
 150         }
 151
 152         return 0;
 153 err:
 154         if (!cstate.enabled)
 155                 clk_disable(priv->clk);
 156
 157         return ret;
 158 }
 159
 160 static void stm32_pwm_lp_get_state(struct pwm_chip *chip,
 161                                    struct pwm_device *pwm,
 162                                    struct pwm_state *state)
 163 {
 164         struct stm32_pwm_lp *priv = to_stm32_pwm_lp(chip);
 165         unsigned long rate = clk_get_rate(priv->clk);
 166         u32 val, presc, prd;
 167         u64 tmp;
 168
 169         regmap_read(priv->regmap, STM32_LPTIM_CR, &val);
 170         state->enabled = !!FIELD_GET(STM32_LPTIM_ENABLE, val);
 171         /* Keep PWM counter clock refcount in sync with PWM initial state */
 172         if (state->enabled)
 173                 clk_enable(priv->clk);
 174
 175         regmap_read(priv->regmap, STM32_LPTIM_CFGR, &val);
 176         presc = FIELD_GET(STM32_LPTIM_PRESC, val);
 177         state->polarity = FIELD_GET(STM32_LPTIM_WAVPOL, val);
 178
 179         regmap_read(priv->regmap, STM32_LPTIM_ARR, &prd);
 180         tmp = prd + 1;
 181         tmp = (tmp << presc) * NSEC_PER_SEC;
 182         state->period = DIV_ROUND_CLOSEST_ULL(tmp, rate);
 183
 184         regmap_read(priv->regmap, STM32_LPTIM_CMP, &val);
 185         tmp = prd - val;
 186         tmp = (tmp << presc) * NSEC_PER_SEC;
 187         state->duty_cycle = DIV_ROUND_CLOSEST_ULL(tmp, rate);
 188 }
 189
 190 static const struct pwm_ops stm32_pwm_lp_ops = {
 191         .owner = THIS_MODULE,
 192         .apply = stm32_pwm_lp_apply,
 193         .get_state = stm32_pwm_lp_get_state,
 194 };
 195
 196 static int stm32_pwm_lp_probe(struct platform_device *pdev)
 197 {
 198         struct stm32_lptimer *ddata = dev_get_drvdata(pdev->dev.parent);
 199         struct stm32_pwm_lp *priv;
 200         int ret;
 201
 202         priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
 203         if (!priv)
 204                 return -ENOMEM;
 205
 206         priv->regmap = ddata->regmap;
 207         priv->clk = ddata->clk;
 208         priv->chip.base = -1;
 209         priv->chip.dev = &pdev->dev;
 210         priv->chip.ops = &stm32_pwm_lp_ops;
 211         priv->chip.npwm = 1;
 212
 213         ret = pwmchip_add(&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 stm32_pwm_lp_remove(struct platform_device *pdev)
 223 {
 224         struct stm32_pwm_lp *priv = platform_get_drvdata(pdev);
 225         unsigned int i;
 226
 227         for (i = 0; i < priv->chip.npwm; i++)
 228                 if (pwm_is_enabled(&priv->chip.pwms[i]))
 229                         pwm_disable(&priv->chip.pwms[i]);
 230
 231         return pwmchip_remove(&priv->chip);
 232 }
 233
 234 static const struct of_device_id stm32_pwm_lp_of_match[] = {
 235         { .compatible = "st,stm32-pwm-lp", },
 236         {},
 237 };
 238 MODULE_DEVICE_TABLE(of, stm32_pwm_lp_of_match);
 239
 240 static struct platform_driver stm32_pwm_lp_driver = {
 241         .probe  = stm32_pwm_lp_probe,
 242         .remove = stm32_pwm_lp_remove,
 243         .driver = {
 244                 .name = "stm32-pwm-lp",
 245                 .of_match_table = of_match_ptr(stm32_pwm_lp_of_match),
 246         },
 247 };
 248 module_platform_driver(stm32_pwm_lp_driver);
 249
 250 MODULE_ALIAS("platform:stm32-pwm-lp");
 251 MODULE_DESCRIPTION("STMicroelectronics STM32 PWM LP driver");
 252 MODULE_LICENSE("GPL v2");