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pwm: iqs620a: Correct a stale state variable

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If duty cycle is first set to a value that is sufficiently high to
enable the output (e.g. 10000 ns) but then lowered to a value that
is quantized to zero (e.g. 1000 ns), the output is disabled as the
device cannot drive a constant zero (as expected).

However if the device is later re-initialized due to watchdog bite,
the output is re-enabled at the next-to-last duty cycle (10000 ns).
This is because the iqs620_pwm->out_en flag unconditionally tracks
state->enabled instead of what was actually written to the device.

To solve this problem, use one state variable that encodes all 257
states of the output (duty_scale) with 0 representing tri-state, 1
representing the minimum available duty cycle and 256 representing
100% duty cycle.

Signed-off-by: Jeff LaBundy <jeff@labundy.com>
Reviewed-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
This commit is contained in:
Jeff LaBundy 2021-01-18 22:30:29 -06:00 committed by Thierry Reding
parent 72d6b2459d
commit 28208c7b4a
1 changed files with 37 additions and 51 deletions
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88
drivers/pwm/pwm-iqs620a.c
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@ -37,15 +37,32 @@ struct iqs620_pwm_private {
struct pwm_chip chip;
struct notifier_block notifier;
struct mutex lock;
bool out_en;
u8 duty_val;
unsigned int duty_scale;
};
static int iqs620_pwm_init(struct iqs620_pwm_private *iqs620_pwm,
unsigned int duty_scale)
{
struct iqs62x_core *iqs62x = iqs620_pwm->iqs62x;
int ret;
if (!duty_scale)
return regmap_update_bits(iqs62x->regmap, IQS620_PWR_SETTINGS,
IQS620_PWR_SETTINGS_PWM_OUT, 0);
ret = regmap_write(iqs62x->regmap, IQS620_PWM_DUTY_CYCLE,
duty_scale - 1);
if (ret)
return ret;
return regmap_update_bits(iqs62x->regmap, IQS620_PWR_SETTINGS,
IQS620_PWR_SETTINGS_PWM_OUT, 0xff);
}
static int iqs620_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
const struct pwm_state *state)
{
struct iqs620_pwm_private *iqs620_pwm;
struct iqs62x_core *iqs62x;
unsigned int duty_cycle;
unsigned int duty_scale;
int ret;
@ -57,7 +74,6 @@ static int iqs620_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
return -EINVAL;
iqs620_pwm = container_of(chip, struct iqs620_pwm_private, chip);
iqs62x = iqs620_pwm->iqs62x;
/*
* The duty cycle generated by the device is calculated as follows:
@ -74,36 +90,15 @@ static int iqs620_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
duty_cycle = min_t(u64, state->duty_cycle, IQS620_PWM_PERIOD_NS);
duty_scale = duty_cycle * 256 / IQS620_PWM_PERIOD_NS;
if (!state->enabled)
duty_scale = 0;
mutex_lock(&iqs620_pwm->lock);
if (!state->enabled || !duty_scale) {
ret = regmap_update_bits(iqs62x->regmap, IQS620_PWR_SETTINGS,
IQS620_PWR_SETTINGS_PWM_OUT, 0);
if (ret)
goto err_mutex;
}
ret = iqs620_pwm_init(iqs620_pwm, duty_scale);
if (!ret)
iqs620_pwm->duty_scale = duty_scale;
if (duty_scale) {
u8 duty_val = duty_scale - 1;
ret = regmap_write(iqs62x->regmap, IQS620_PWM_DUTY_CYCLE,
duty_val);
if (ret)
goto err_mutex;
iqs620_pwm->duty_val = duty_val;
}
if (state->enabled && duty_scale) {
ret = regmap_update_bits(iqs62x->regmap, IQS620_PWR_SETTINGS,
IQS620_PWR_SETTINGS_PWM_OUT, 0xff);
if (ret)
goto err_mutex;
}
iqs620_pwm->out_en = state->enabled;
err_mutex:
mutex_unlock(&iqs620_pwm->lock);
return ret;
@ -121,12 +116,11 @@ static void iqs620_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
/*
* Since the device cannot generate a 0% duty cycle, requests to do so
* cause subsequent calls to iqs620_pwm_get_state to report the output
* as disabled with duty cycle equal to that which was in use prior to
* the request. This is not ideal, but is the best compromise based on
* as disabled. This is not ideal, but is the best compromise based on
* the capabilities of the device.
*/
state->enabled = iqs620_pwm->out_en;
state->duty_cycle = DIV_ROUND_UP((iqs620_pwm->duty_val + 1) *
state->enabled = iqs620_pwm->duty_scale > 0;
state->duty_cycle = DIV_ROUND_UP(iqs620_pwm->duty_scale *
IQS620_PWM_PERIOD_NS, 256);
mutex_unlock(&iqs620_pwm->lock);
@ -138,7 +132,6 @@ static int iqs620_pwm_notifier(struct notifier_block *notifier,
unsigned long event_flags, void *context)
{
struct iqs620_pwm_private *iqs620_pwm;
struct iqs62x_core *iqs62x;
int ret;
if (!(event_flags & BIT(IQS62X_EVENT_SYS_RESET)))
@ -146,7 +139,6 @@ static int iqs620_pwm_notifier(struct notifier_block *notifier,
iqs620_pwm = container_of(notifier, struct iqs620_pwm_private,
notifier);
iqs62x = iqs620_pwm->iqs62x;
mutex_lock(&iqs620_pwm->lock);
@ -155,16 +147,8 @@ static int iqs620_pwm_notifier(struct notifier_block *notifier,
* of a device reset, so nothing else is printed here unless there is
* an additional failure.
*/
ret = regmap_write(iqs62x->regmap, IQS620_PWM_DUTY_CYCLE,
iqs620_pwm->duty_val);
if (ret)
goto err_mutex;
ret = iqs620_pwm_init(iqs620_pwm, iqs620_pwm->duty_scale);
ret = regmap_update_bits(iqs62x->regmap, IQS620_PWR_SETTINGS,
IQS620_PWR_SETTINGS_PWM_OUT,
iqs620_pwm->out_en ? 0xff : 0);
err_mutex:
mutex_unlock(&iqs620_pwm->lock);
if (ret) {
@ -211,12 +195,14 @@ static int iqs620_pwm_probe(struct platform_device *pdev)
ret = regmap_read(iqs62x->regmap, IQS620_PWR_SETTINGS, &val);
if (ret)
return ret;
iqs620_pwm->out_en = val & IQS620_PWR_SETTINGS_PWM_OUT;
ret = regmap_read(iqs62x->regmap, IQS620_PWM_DUTY_CYCLE, &val);
if (ret)
return ret;
iqs620_pwm->duty_val = val;
if (val & IQS620_PWR_SETTINGS_PWM_OUT) {
ret = regmap_read(iqs62x->regmap, IQS620_PWM_DUTY_CYCLE, &val);
if (ret)
return ret;
iqs620_pwm->duty_scale = val + 1;
}
iqs620_pwm->chip.dev = &pdev->dev;
iqs620_pwm->chip.ops = &iqs620_pwm_ops;