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         struct pwm_chip chip;
  28         struct device *dev;
  29         void __iomem *base;
  30         struct clk *clk;
  31 };
  32
  33 static inline struct bcm2835_pwm *to_bcm2835_pwm(struct pwm_chip *chip)
  34 {
  35         return container_of(chip, struct bcm2835_pwm, chip);
  36 }
  37
  38 static int bcm2835_pwm_request(struct pwm_chip *chip, struct pwm_device *pwm)
  39 {
  40         struct bcm2835_pwm *pc = to_bcm2835_pwm(chip);
  41         u32 value;
  42
  43         value = readl(pc->base + PWM_CONTROL);
  44         value &= ~(PWM_CONTROL_MASK << PWM_CONTROL_SHIFT(pwm->hwpwm));
  45         value |= (PWM_MODE << PWM_CONTROL_SHIFT(pwm->hwpwm));
  46         writel(value, pc->base + PWM_CONTROL);
  47
  48         return 0;
  49 }
  50
  51 static void bcm2835_pwm_free(struct pwm_chip *chip, struct pwm_device *pwm)
  52 {
  53         struct bcm2835_pwm *pc = to_bcm2835_pwm(chip);
  54         u32 value;
  55
  56         value = readl(pc->base + PWM_CONTROL);
  57         value &= ~(PWM_CONTROL_MASK << PWM_CONTROL_SHIFT(pwm->hwpwm));
  58         writel(value, pc->base + PWM_CONTROL);
  59 }
  60
  61 static int bcm2835_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
  62                              const struct pwm_state *state)
  63 {
  64
  65         struct bcm2835_pwm *pc = to_bcm2835_pwm(chip);
  66         unsigned long rate = clk_get_rate(pc->clk);
  67         unsigned long long period_cycles;
  68         u64 max_period;
  69
  70         u32 val;
  71
  72         if (!rate) {
  73                 dev_err(pc->dev, "failed to get clock rate\n");
  74                 return -EINVAL;
  75         }
  76
  77         /*
  78          * period_cycles must be a 32 bit value, so period * rate / NSEC_PER_SEC
  79          * must be <= U32_MAX. As U32_MAX * NSEC_PER_SEC < U64_MAX the
  80          * multiplication period * rate doesn't overflow.
  81          * To calculate the maximal possible period that guarantees the
  82          * above inequality:
  83          *
  84          *     round(period * rate / NSEC_PER_SEC) <= U32_MAX
  85          * <=> period * rate / NSEC_PER_SEC < U32_MAX + 0.5
  86          * <=> period * rate < (U32_MAX + 0.5) * NSEC_PER_SEC
  87          * <=> period < ((U32_MAX + 0.5) * NSEC_PER_SEC) / rate
  88          * <=> period < ((U32_MAX * NSEC_PER_SEC + NSEC_PER_SEC/2) / rate
  89          * <=> period <= ceil((U32_MAX * NSEC_PER_SEC + NSEC_PER_SEC/2) / rate) - 1
  90          */
  91         max_period = DIV_ROUND_UP_ULL((u64)U32_MAX * NSEC_PER_SEC + NSEC_PER_SEC / 2, rate) - 1;
  92
  93         if (state->period > max_period)
  94                 return -EINVAL;
  95
  96         /* set period */
  97         period_cycles = DIV_ROUND_CLOSEST_ULL(state->period * rate, NSEC_PER_SEC);
  98
  99         /* don't accept a period that is too small */
 100         if (period_cycles < PERIOD_MIN)
 101                 return -EINVAL;
 102
 103         writel(period_cycles, pc->base + PERIOD(pwm->hwpwm));
 104
 105         /* set duty cycle */
 106         val = DIV_ROUND_CLOSEST_ULL(state->duty_cycle * rate, NSEC_PER_SEC);
 107         writel(val, pc->base + DUTY(pwm->hwpwm));
 108
 109         /* set polarity */
 110         val = readl(pc->base + PWM_CONTROL);
 111
 112         if (state->polarity == PWM_POLARITY_NORMAL)
 113                 val &= ~(PWM_POLARITY << PWM_CONTROL_SHIFT(pwm->hwpwm));
 114         else
 115                 val |= PWM_POLARITY << PWM_CONTROL_SHIFT(pwm->hwpwm);
 116
 117         /* enable/disable */
 118         if (state->enabled)
 119                 val |= PWM_ENABLE << PWM_CONTROL_SHIFT(pwm->hwpwm);
 120         else
 121                 val &= ~(PWM_ENABLE << PWM_CONTROL_SHIFT(pwm->hwpwm));
 122
 123         writel(val, pc->base + PWM_CONTROL);
 124
 125         return 0;
 126 }
 127
 128 static const struct pwm_ops bcm2835_pwm_ops = {
 129         .request = bcm2835_pwm_request,
 130         .free = bcm2835_pwm_free,
 131         .apply = bcm2835_pwm_apply,
 132         .owner = THIS_MODULE,
 133 };
 134
 135 static int bcm2835_pwm_probe(struct platform_device *pdev)
 136 {
 137         struct bcm2835_pwm *pc;
 138         int ret;
 139
 140         pc = devm_kzalloc(&pdev->dev, sizeof(*pc), GFP_KERNEL);
 141         if (!pc)
 142                 return -ENOMEM;
 143
 144         pc->dev = &pdev->dev;
 145
 146         pc->base = devm_platform_ioremap_resource(pdev, 0);
 147         if (IS_ERR(pc->base))
 148                 return PTR_ERR(pc->base);
 149
 150         pc->clk = devm_clk_get(&pdev->dev, NULL);
 151         if (IS_ERR(pc->clk))
 152                 return dev_err_probe(&pdev->dev, PTR_ERR(pc->clk),
 153                                      "clock not found\n");
 154
 155         ret = clk_prepare_enable(pc->clk);
 156         if (ret)
 157                 return ret;
 158
 159         pc->chip.dev = &pdev->dev;
 160         pc->chip.ops = &bcm2835_pwm_ops;
 161         pc->chip.npwm = 2;
 162
 163         platform_set_drvdata(pdev, pc);
 164
 165         ret = pwmchip_add(&pc->chip);
 166         if (ret < 0)
 167                 goto add_fail;
 168
 169         return 0;
 170
 171 add_fail:
 172         clk_disable_unprepare(pc->clk);
 173         return ret;
 174 }
 175
 176 static void bcm2835_pwm_remove(struct platform_device *pdev)
 177 {
 178         struct bcm2835_pwm *pc = platform_get_drvdata(pdev);
 179
 180         pwmchip_remove(&pc->chip);
 181
 182         clk_disable_unprepare(pc->clk);
 183 }
 184
 185 static const struct of_device_id bcm2835_pwm_of_match[] = {
 186         { .compatible = "brcm,bcm2835-pwm", },
 187         { /* sentinel */ }
 188 };
 189 MODULE_DEVICE_TABLE(of, bcm2835_pwm_of_match);
 190
 191 static struct platform_driver bcm2835_pwm_driver = {
 192         .driver = {
 193                 .name = "bcm2835-pwm",
 194                 .of_match_table = bcm2835_pwm_of_match,
 195         },
 196         .probe = bcm2835_pwm_probe,
 197         .remove_new = bcm2835_pwm_remove,
 198 };
 199 module_platform_driver(bcm2835_pwm_driver);
 200
 201 MODULE_AUTHOR("Bart Tanghe <bart.tanghe@thomasmore.be>");
 202 MODULE_DESCRIPTION("Broadcom BCM2835 PWM driver");
 203 MODULE_LICENSE("GPL v2");