drivers/pwm/pwm-bcm2835.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Copyright 2014 Bart Tanghe <bart.tanghe@thomasmore.be>
   4  */
   5
   6 #include <linux/clk.h>
   7 #include <linux/err.h>
   8 #include <linux/io.h>
   9 #include <linux/module.h>
  10 #include <linux/of.h>
  11 #include <linux/platform_device.h>
  12 #include <linux/pwm.h>
  13
  14 #define PWM_CONTROL             0x000
  15 #define PWM_CONTROL_SHIFT(x)    ((x) * 8)
  16 #define PWM_CONTROL_MASK        0xff
  17 #define PWM_MODE                0x80            /* set timer in PWM mode */
  18 #define PWM_ENABLE              (1 << 0)
  19 #define PWM_POLARITY            (1 << 4)
  20
  21 #define PERIOD(x)               (((x) * 0x10) + 0x10)
  22 #define DUTY(x)                 (((x) * 0x10) + 0x14)
  23
  24 #define PERIOD_MIN              0x2
  25
  26 struct bcm2835_pwm {
  27         void __iomem *base;
  28         struct clk *clk;
  29         unsigned long rate;
  30 };
  31
  32 static inline struct bcm2835_pwm *to_bcm2835_pwm(struct pwm_chip *chip)
  33 {
  34         return pwmchip_get_drvdata(chip);
  35 }
  36
  37 static int bcm2835_pwm_request(struct pwm_chip *chip, struct pwm_device *pwm)
  38 {
  39         struct bcm2835_pwm *pc = to_bcm2835_pwm(chip);
  40         u32 value;
  41
  42         value = readl(pc->base + PWM_CONTROL);
  43         value &= ~(PWM_CONTROL_MASK << PWM_CONTROL_SHIFT(pwm->hwpwm));
  44         value |= (PWM_MODE << PWM_CONTROL_SHIFT(pwm->hwpwm));
  45         writel(value, pc->base + PWM_CONTROL);
  46
  47         return 0;
  48 }
  49
  50 static void bcm2835_pwm_free(struct pwm_chip *chip, struct pwm_device *pwm)
  51 {
  52         struct bcm2835_pwm *pc = to_bcm2835_pwm(chip);
  53         u32 value;
  54
  55         value = readl(pc->base + PWM_CONTROL);
  56         value &= ~(PWM_CONTROL_MASK << PWM_CONTROL_SHIFT(pwm->hwpwm));
  57         writel(value, pc->base + PWM_CONTROL);
  58 }
  59
  60 static int bcm2835_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
  61                              const struct pwm_state *state)
  62 {
  63
  64         struct bcm2835_pwm *pc = to_bcm2835_pwm(chip);
  65         unsigned long long period_cycles;
  66         u64 max_period;
  67
  68         u32 val;
  69
  70         /*
  71          * period_cycles must be a 32 bit value, so period * rate / NSEC_PER_SEC
  72          * must be <= U32_MAX. As U32_MAX * NSEC_PER_SEC < U64_MAX the
  73          * multiplication period * rate doesn't overflow.
  74          * To calculate the maximal possible period that guarantees the
  75          * above inequality:
  76          *
  77          *     round(period * rate / NSEC_PER_SEC) <= U32_MAX
  78          * <=> period * rate / NSEC_PER_SEC < U32_MAX + 0.5
  79          * <=> period * rate < (U32_MAX + 0.5) * NSEC_PER_SEC
  80          * <=> period < ((U32_MAX + 0.5) * NSEC_PER_SEC) / rate
  81          * <=> period < ((U32_MAX * NSEC_PER_SEC + NSEC_PER_SEC/2) / rate
  82          * <=> period <= ceil((U32_MAX * NSEC_PER_SEC + NSEC_PER_SEC/2) / rate) - 1
  83          */
  84         max_period = DIV_ROUND_UP_ULL((u64)U32_MAX * NSEC_PER_SEC + NSEC_PER_SEC / 2, pc->rate) - 1;
  85
  86         if (state->period > max_period)
  87                 return -EINVAL;
  88
  89         /* set period */
  90         period_cycles = DIV_ROUND_CLOSEST_ULL(state->period * pc->rate, NSEC_PER_SEC);
  91
  92         /* don't accept a period that is too small */
  93         if (period_cycles < PERIOD_MIN)
  94                 return -EINVAL;
  95
  96         writel(period_cycles, pc->base + PERIOD(pwm->hwpwm));
  97
  98         /* set duty cycle */
  99         val = DIV_ROUND_CLOSEST_ULL(state->duty_cycle * pc->rate, NSEC_PER_SEC);
 100         writel(val, pc->base + DUTY(pwm->hwpwm));
 101
 102         /* set polarity */
 103         val = readl(pc->base + PWM_CONTROL);
 104
 105         if (state->polarity == PWM_POLARITY_NORMAL)
 106                 val &= ~(PWM_POLARITY << PWM_CONTROL_SHIFT(pwm->hwpwm));
 107         else
 108                 val |= PWM_POLARITY << PWM_CONTROL_SHIFT(pwm->hwpwm);
 109
 110         /* enable/disable */
 111         if (state->enabled)
 112                 val |= PWM_ENABLE << PWM_CONTROL_SHIFT(pwm->hwpwm);
 113         else
 114                 val &= ~(PWM_ENABLE << PWM_CONTROL_SHIFT(pwm->hwpwm));
 115
 116         writel(val, pc->base + PWM_CONTROL);
 117
 118         return 0;
 119 }
 120
 121 static const struct pwm_ops bcm2835_pwm_ops = {
 122         .request = bcm2835_pwm_request,
 123         .free = bcm2835_pwm_free,
 124         .apply = bcm2835_pwm_apply,
 125 };
 126
 127 static int bcm2835_pwm_probe(struct platform_device *pdev)
 128 {
 129         struct device *dev = &pdev->dev;
 130         struct pwm_chip *chip;
 131         struct bcm2835_pwm *pc;
 132         int ret;
 133
 134         chip = devm_pwmchip_alloc(dev, 2, sizeof(*pc));
 135         if (IS_ERR(chip))
 136                 return PTR_ERR(chip);
 137         pc = to_bcm2835_pwm(chip);
 138
 139         pc->base = devm_platform_ioremap_resource(pdev, 0);
 140         if (IS_ERR(pc->base))
 141                 return PTR_ERR(pc->base);
 142
 143         pc->clk = devm_clk_get_enabled(dev, NULL);
 144         if (IS_ERR(pc->clk))
 145                 return dev_err_probe(dev, PTR_ERR(pc->clk),
 146                                      "clock not found\n");
 147
 148         ret = devm_clk_rate_exclusive_get(dev, pc->clk);
 149         if (ret)
 150                 return dev_err_probe(dev, ret,
 151                                      "fail to get exclusive rate\n");
 152
 153         pc->rate = clk_get_rate(pc->clk);
 154         if (!pc->rate)
 155                 return dev_err_probe(dev, -EINVAL,
 156                                      "failed to get clock rate\n");
 157
 158         chip->ops = &bcm2835_pwm_ops;
 159         chip->atomic = true;
 160
 161         platform_set_drvdata(pdev, pc);
 162
 163         ret = devm_pwmchip_add(dev, chip);
 164         if (ret < 0)
 165                 return dev_err_probe(dev, ret, "failed to add pwmchip\n");
 166
 167         return 0;
 168 }
 169
 170 static int bcm2835_pwm_suspend(struct device *dev)
 171 {
 172         struct bcm2835_pwm *pc = dev_get_drvdata(dev);
 173
 174         clk_disable_unprepare(pc->clk);
 175
 176         return 0;
 177 }
 178
 179 static int bcm2835_pwm_resume(struct device *dev)
 180 {
 181         struct bcm2835_pwm *pc = dev_get_drvdata(dev);
 182
 183         return clk_prepare_enable(pc->clk);
 184 }
 185
 186 static DEFINE_SIMPLE_DEV_PM_OPS(bcm2835_pwm_pm_ops, bcm2835_pwm_suspend,
 187                                 bcm2835_pwm_resume);
 188
 189 static const struct of_device_id bcm2835_pwm_of_match[] = {
 190         { .compatible = "brcm,bcm2835-pwm", },
 191         { /* sentinel */ }
 192 };
 193 MODULE_DEVICE_TABLE(of, bcm2835_pwm_of_match);
 194
 195 static struct platform_driver bcm2835_pwm_driver = {
 196         .driver = {
 197                 .name = "bcm2835-pwm",
 198                 .of_match_table = bcm2835_pwm_of_match,
 199                 .pm = pm_ptr(&bcm2835_pwm_pm_ops),
 200         },
 201         .probe = bcm2835_pwm_probe,
 202 };
 203 module_platform_driver(bcm2835_pwm_driver);
 204
 205 MODULE_AUTHOR("Bart Tanghe <bart.tanghe@thomasmore.be>");
 206 MODULE_DESCRIPTION("Broadcom BCM2835 PWM driver");
 207 MODULE_LICENSE("GPL v2");