linux/drivers/pwm/pwm-jz4740.c
Uwe Kleine-König 71523d1812 pwm: Ensure pwm_apply_state() doesn't modify the state argument
It is surprising for a PWM consumer when the variable holding the
requested state is modified by pwm_apply_state(). Consider for example a
driver doing:

        #define PERIOD 5000000
        #define DUTY_LITTLE 10
        ...
        struct pwm_state state = {
                .period = PERIOD,
                .duty_cycle = DUTY_LITTLE,
                .polarity = PWM_POLARITY_NORMAL,
                .enabled = true,
        };

        pwm_apply_state(mypwm, &state);
        ...
        state.duty_cycle = PERIOD / 2;
        pwm_apply_state(mypwm, &state);

For sure the second call to pwm_apply_state() should still have
state.period = PERIOD and not something the hardware driver chose for a
reason that doesn't necessarily apply to the second call.

So declare the state argument as a pointer to a const type and adapt all
drivers' .apply callbacks.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
2019-09-21 03:25:10 +02:00

206 lines
4.8 KiB
C

// SPDX-License-Identifier: GPL-2.0-or-later
/*
* Copyright (C) 2010, Lars-Peter Clausen <lars@metafoo.de>
* JZ4740 platform PWM support
*
* Limitations:
* - The .apply callback doesn't complete the currently running period before
* reconfiguring the hardware.
* - Each period starts with the inactive part.
*/
#include <linux/clk.h>
#include <linux/err.h>
#include <linux/gpio.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/of_device.h>
#include <linux/platform_device.h>
#include <linux/pwm.h>
#include <asm/mach-jz4740/timer.h>
#define NUM_PWM 8
struct jz4740_pwm_chip {
struct pwm_chip chip;
struct clk *clk;
};
static inline struct jz4740_pwm_chip *to_jz4740(struct pwm_chip *chip)
{
return container_of(chip, struct jz4740_pwm_chip, chip);
}
static int jz4740_pwm_request(struct pwm_chip *chip, struct pwm_device *pwm)
{
/*
* Timers 0 and 1 are used for system tasks, so they are unavailable
* for use as PWMs.
*/
if (pwm->hwpwm < 2)
return -EBUSY;
jz4740_timer_start(pwm->hwpwm);
return 0;
}
static void jz4740_pwm_free(struct pwm_chip *chip, struct pwm_device *pwm)
{
jz4740_timer_set_ctrl(pwm->hwpwm, 0);
jz4740_timer_stop(pwm->hwpwm);
}
static int jz4740_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
{
uint32_t ctrl = jz4740_timer_get_ctrl(pwm->pwm);
ctrl |= JZ_TIMER_CTRL_PWM_ENABLE;
jz4740_timer_set_ctrl(pwm->hwpwm, ctrl);
jz4740_timer_enable(pwm->hwpwm);
return 0;
}
static void jz4740_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
{
uint32_t ctrl = jz4740_timer_get_ctrl(pwm->hwpwm);
/*
* Set duty > period. This trick allows the TCU channels in TCU2 mode to
* properly return to their init level.
*/
jz4740_timer_set_duty(pwm->hwpwm, 0xffff);
jz4740_timer_set_period(pwm->hwpwm, 0x0);
/*
* Disable PWM output.
* In TCU2 mode (channel 1/2 on JZ4750+), this must be done before the
* counter is stopped, while in TCU1 mode the order does not matter.
*/
ctrl &= ~JZ_TIMER_CTRL_PWM_ENABLE;
jz4740_timer_set_ctrl(pwm->hwpwm, ctrl);
/* Stop counter */
jz4740_timer_disable(pwm->hwpwm);
}
static int jz4740_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
const struct pwm_state *state)
{
struct jz4740_pwm_chip *jz4740 = to_jz4740(pwm->chip);
unsigned long long tmp;
unsigned long period, duty;
unsigned int prescaler = 0;
uint16_t ctrl;
tmp = (unsigned long long)clk_get_rate(jz4740->clk) * state->period;
do_div(tmp, 1000000000);
period = tmp;
while (period > 0xffff && prescaler < 6) {
period >>= 2;
++prescaler;
}
if (prescaler == 6)
return -EINVAL;
tmp = (unsigned long long)period * state->duty_cycle;
do_div(tmp, state->period);
duty = period - tmp;
if (duty >= period)
duty = period - 1;
jz4740_pwm_disable(chip, pwm);
jz4740_timer_set_count(pwm->hwpwm, 0);
jz4740_timer_set_duty(pwm->hwpwm, duty);
jz4740_timer_set_period(pwm->hwpwm, period);
ctrl = JZ_TIMER_CTRL_PRESCALER(prescaler) | JZ_TIMER_CTRL_SRC_EXT |
JZ_TIMER_CTRL_PWM_ABBRUPT_SHUTDOWN;
jz4740_timer_set_ctrl(pwm->hwpwm, ctrl);
switch (state->polarity) {
case PWM_POLARITY_NORMAL:
ctrl &= ~JZ_TIMER_CTRL_PWM_ACTIVE_LOW;
break;
case PWM_POLARITY_INVERSED:
ctrl |= JZ_TIMER_CTRL_PWM_ACTIVE_LOW;
break;
}
jz4740_timer_set_ctrl(pwm->hwpwm, ctrl);
if (state->enabled)
jz4740_pwm_enable(chip, pwm);
return 0;
}
static const struct pwm_ops jz4740_pwm_ops = {
.request = jz4740_pwm_request,
.free = jz4740_pwm_free,
.apply = jz4740_pwm_apply,
.owner = THIS_MODULE,
};
static int jz4740_pwm_probe(struct platform_device *pdev)
{
struct jz4740_pwm_chip *jz4740;
jz4740 = devm_kzalloc(&pdev->dev, sizeof(*jz4740), GFP_KERNEL);
if (!jz4740)
return -ENOMEM;
jz4740->clk = devm_clk_get(&pdev->dev, "ext");
if (IS_ERR(jz4740->clk))
return PTR_ERR(jz4740->clk);
jz4740->chip.dev = &pdev->dev;
jz4740->chip.ops = &jz4740_pwm_ops;
jz4740->chip.npwm = NUM_PWM;
jz4740->chip.base = -1;
jz4740->chip.of_xlate = of_pwm_xlate_with_flags;
jz4740->chip.of_pwm_n_cells = 3;
platform_set_drvdata(pdev, jz4740);
return pwmchip_add(&jz4740->chip);
}
static int jz4740_pwm_remove(struct platform_device *pdev)
{
struct jz4740_pwm_chip *jz4740 = platform_get_drvdata(pdev);
return pwmchip_remove(&jz4740->chip);
}
#ifdef CONFIG_OF
static const struct of_device_id jz4740_pwm_dt_ids[] = {
{ .compatible = "ingenic,jz4740-pwm", },
{},
};
MODULE_DEVICE_TABLE(of, jz4740_pwm_dt_ids);
#endif
static struct platform_driver jz4740_pwm_driver = {
.driver = {
.name = "jz4740-pwm",
.of_match_table = of_match_ptr(jz4740_pwm_dt_ids),
},
.probe = jz4740_pwm_probe,
.remove = jz4740_pwm_remove,
};
module_platform_driver(jz4740_pwm_driver);
MODULE_AUTHOR("Lars-Peter Clausen <lars@metafoo.de>");
MODULE_DESCRIPTION("Ingenic JZ4740 PWM driver");
MODULE_ALIAS("platform:jz4740-pwm");
MODULE_LICENSE("GPL");