diff options
Diffstat (limited to 'drivers/pwm/pwm-bcm2835.c')
| -rw-r--r-- | drivers/pwm/pwm-bcm2835.c | 205 |
1 files changed, 205 insertions, 0 deletions
diff --git a/drivers/pwm/pwm-bcm2835.c b/drivers/pwm/pwm-bcm2835.c new file mode 100644 index 000000000..50b8594be --- /dev/null +++ b/drivers/pwm/pwm-bcm2835.c @@ -0,0 +1,205 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright 2014 Bart Tanghe <bart.tanghe@thomasmore.be> + */ + +#include <linux/clk.h> +#include <linux/err.h> +#include <linux/io.h> +#include <linux/module.h> +#include <linux/of.h> +#include <linux/platform_device.h> +#include <linux/pwm.h> + +#define PWM_CONTROL 0x000 +#define PWM_CONTROL_SHIFT(x) ((x) * 8) +#define PWM_CONTROL_MASK 0xff +#define PWM_MODE 0x80 /* set timer in PWM mode */ +#define PWM_ENABLE (1 << 0) +#define PWM_POLARITY (1 << 4) + +#define PERIOD(x) (((x) * 0x10) + 0x10) +#define DUTY(x) (((x) * 0x10) + 0x14) + +#define PERIOD_MIN 0x2 + +struct bcm2835_pwm { + struct pwm_chip chip; + struct device *dev; + void __iomem *base; + struct clk *clk; +}; + +static inline struct bcm2835_pwm *to_bcm2835_pwm(struct pwm_chip *chip) +{ + return container_of(chip, struct bcm2835_pwm, chip); +} + +static int bcm2835_pwm_request(struct pwm_chip *chip, struct pwm_device *pwm) +{ + struct bcm2835_pwm *pc = to_bcm2835_pwm(chip); + u32 value; + + value = readl(pc->base + PWM_CONTROL); + value &= ~(PWM_CONTROL_MASK << PWM_CONTROL_SHIFT(pwm->hwpwm)); + value |= (PWM_MODE << PWM_CONTROL_SHIFT(pwm->hwpwm)); + writel(value, pc->base + PWM_CONTROL); + + return 0; +} + +static void bcm2835_pwm_free(struct pwm_chip *chip, struct pwm_device *pwm) +{ + struct bcm2835_pwm *pc = to_bcm2835_pwm(chip); + u32 value; + + value = readl(pc->base + PWM_CONTROL); + value &= ~(PWM_CONTROL_MASK << PWM_CONTROL_SHIFT(pwm->hwpwm)); + writel(value, pc->base + PWM_CONTROL); +} + +static int bcm2835_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm, + const struct pwm_state *state) +{ + + struct bcm2835_pwm *pc = to_bcm2835_pwm(chip); + unsigned long rate = clk_get_rate(pc->clk); + unsigned long long period_cycles; + u64 max_period; + + u32 val; + + if (!rate) { + dev_err(pc->dev, "failed to get clock rate\n"); + return -EINVAL; + } + + /* + * period_cycles must be a 32 bit value, so period * rate / NSEC_PER_SEC + * must be <= U32_MAX. As U32_MAX * NSEC_PER_SEC < U64_MAX the + * multiplication period * rate doesn't overflow. + * To calculate the maximal possible period that guarantees the + * above inequality: + * + * round(period * rate / NSEC_PER_SEC) <= U32_MAX + * <=> period * rate / NSEC_PER_SEC < U32_MAX + 0.5 + * <=> period * rate < (U32_MAX + 0.5) * NSEC_PER_SEC + * <=> period < ((U32_MAX + 0.5) * NSEC_PER_SEC) / rate + * <=> period < ((U32_MAX * NSEC_PER_SEC + NSEC_PER_SEC/2) / rate + * <=> period <= ceil((U32_MAX * NSEC_PER_SEC + NSEC_PER_SEC/2) / rate) - 1 + */ + max_period = DIV_ROUND_UP_ULL((u64)U32_MAX * NSEC_PER_SEC + NSEC_PER_SEC / 2, rate) - 1; + + if (state->period > max_period) + return -EINVAL; + + /* set period */ + period_cycles = DIV_ROUND_CLOSEST_ULL(state->period * rate, NSEC_PER_SEC); + + /* don't accept a period that is too small */ + if (period_cycles < PERIOD_MIN) + return -EINVAL; + + writel(period_cycles, pc->base + PERIOD(pwm->hwpwm)); + + /* set duty cycle */ + val = DIV_ROUND_CLOSEST_ULL(state->duty_cycle * rate, NSEC_PER_SEC); + writel(val, pc->base + DUTY(pwm->hwpwm)); + + /* set polarity */ + val = readl(pc->base + PWM_CONTROL); + + if (state->polarity == PWM_POLARITY_NORMAL) + val &= ~(PWM_POLARITY << PWM_CONTROL_SHIFT(pwm->hwpwm)); + else + val |= PWM_POLARITY << PWM_CONTROL_SHIFT(pwm->hwpwm); + + /* enable/disable */ + if (state->enabled) + val |= PWM_ENABLE << PWM_CONTROL_SHIFT(pwm->hwpwm); + else + val &= ~(PWM_ENABLE << PWM_CONTROL_SHIFT(pwm->hwpwm)); + + writel(val, pc->base + PWM_CONTROL); + + return 0; +} + +static const struct pwm_ops bcm2835_pwm_ops = { + .request = bcm2835_pwm_request, + .free = bcm2835_pwm_free, + .apply = bcm2835_pwm_apply, + .owner = THIS_MODULE, +}; + +static int bcm2835_pwm_probe(struct platform_device *pdev) +{ + struct bcm2835_pwm *pc; + int ret; + + pc = devm_kzalloc(&pdev->dev, sizeof(*pc), GFP_KERNEL); + if (!pc) + return -ENOMEM; + + pc->dev = &pdev->dev; + + pc->base = devm_platform_ioremap_resource(pdev, 0); + if (IS_ERR(pc->base)) + return PTR_ERR(pc->base); + + pc->clk = devm_clk_get(&pdev->dev, NULL); + if (IS_ERR(pc->clk)) + return dev_err_probe(&pdev->dev, PTR_ERR(pc->clk), + "clock not found\n"); + + ret = clk_prepare_enable(pc->clk); + if (ret) + return ret; + + pc->chip.dev = &pdev->dev; + pc->chip.ops = &bcm2835_pwm_ops; + pc->chip.npwm = 2; + + platform_set_drvdata(pdev, pc); + + ret = pwmchip_add(&pc->chip); + if (ret < 0) + goto add_fail; + + return 0; + +add_fail: + clk_disable_unprepare(pc->clk); + return ret; +} + +static int bcm2835_pwm_remove(struct platform_device *pdev) +{ + struct bcm2835_pwm *pc = platform_get_drvdata(pdev); + + pwmchip_remove(&pc->chip); + + clk_disable_unprepare(pc->clk); + + return 0; +} + +static const struct of_device_id bcm2835_pwm_of_match[] = { + { .compatible = "brcm,bcm2835-pwm", }, + { /* sentinel */ } +}; +MODULE_DEVICE_TABLE(of, bcm2835_pwm_of_match); + +static struct platform_driver bcm2835_pwm_driver = { + .driver = { + .name = "bcm2835-pwm", + .of_match_table = bcm2835_pwm_of_match, + }, + .probe = bcm2835_pwm_probe, + .remove = bcm2835_pwm_remove, +}; +module_platform_driver(bcm2835_pwm_driver); + +MODULE_AUTHOR("Bart Tanghe <bart.tanghe@thomasmore.be>"); +MODULE_DESCRIPTION("Broadcom BCM2835 PWM driver"); +MODULE_LICENSE("GPL v2"); |