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// 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,
};
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 void bcm2835_pwm_remove(struct platform_device *pdev)
{
struct bcm2835_pwm *pc = platform_get_drvdata(pdev);
pwmchip_remove(&pc->chip);
clk_disable_unprepare(pc->clk);
}
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_new = 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");
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