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pwm: iqs620a: Correct a stale state variable
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:
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72d6b2459d
commit
28208c7b4a
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@ -37,15 +37,32 @@ struct iqs620_pwm_private {
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struct pwm_chip chip;
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struct pwm_chip chip;
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struct notifier_block notifier;
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struct notifier_block notifier;
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struct mutex lock;
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struct mutex lock;
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bool out_en;
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unsigned int duty_scale;
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u8 duty_val;
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};
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};
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static int iqs620_pwm_init(struct iqs620_pwm_private *iqs620_pwm,
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unsigned int duty_scale)
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{
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struct iqs62x_core *iqs62x = iqs620_pwm->iqs62x;
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int ret;
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if (!duty_scale)
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return regmap_update_bits(iqs62x->regmap, IQS620_PWR_SETTINGS,
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IQS620_PWR_SETTINGS_PWM_OUT, 0);
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ret = regmap_write(iqs62x->regmap, IQS620_PWM_DUTY_CYCLE,
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duty_scale - 1);
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if (ret)
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return ret;
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return regmap_update_bits(iqs62x->regmap, IQS620_PWR_SETTINGS,
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IQS620_PWR_SETTINGS_PWM_OUT, 0xff);
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}
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static int iqs620_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
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static int iqs620_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
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const struct pwm_state *state)
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const struct pwm_state *state)
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{
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{
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struct iqs620_pwm_private *iqs620_pwm;
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struct iqs620_pwm_private *iqs620_pwm;
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struct iqs62x_core *iqs62x;
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unsigned int duty_cycle;
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unsigned int duty_cycle;
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unsigned int duty_scale;
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unsigned int duty_scale;
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int ret;
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int ret;
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@ -57,7 +74,6 @@ static int iqs620_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
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return -EINVAL;
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return -EINVAL;
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iqs620_pwm = container_of(chip, struct iqs620_pwm_private, chip);
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iqs620_pwm = container_of(chip, struct iqs620_pwm_private, chip);
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iqs62x = iqs620_pwm->iqs62x;
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/*
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/*
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* The duty cycle generated by the device is calculated as follows:
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* The duty cycle generated by the device is calculated as follows:
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@ -74,36 +90,15 @@ static int iqs620_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
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duty_cycle = min_t(u64, state->duty_cycle, IQS620_PWM_PERIOD_NS);
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duty_cycle = min_t(u64, state->duty_cycle, IQS620_PWM_PERIOD_NS);
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duty_scale = duty_cycle * 256 / IQS620_PWM_PERIOD_NS;
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duty_scale = duty_cycle * 256 / IQS620_PWM_PERIOD_NS;
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if (!state->enabled)
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duty_scale = 0;
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mutex_lock(&iqs620_pwm->lock);
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mutex_lock(&iqs620_pwm->lock);
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if (!state->enabled || !duty_scale) {
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ret = iqs620_pwm_init(iqs620_pwm, duty_scale);
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ret = regmap_update_bits(iqs62x->regmap, IQS620_PWR_SETTINGS,
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if (!ret)
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IQS620_PWR_SETTINGS_PWM_OUT, 0);
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iqs620_pwm->duty_scale = duty_scale;
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if (ret)
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goto err_mutex;
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}
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if (duty_scale) {
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u8 duty_val = duty_scale - 1;
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ret = regmap_write(iqs62x->regmap, IQS620_PWM_DUTY_CYCLE,
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duty_val);
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if (ret)
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goto err_mutex;
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iqs620_pwm->duty_val = duty_val;
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}
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if (state->enabled && duty_scale) {
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ret = regmap_update_bits(iqs62x->regmap, IQS620_PWR_SETTINGS,
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IQS620_PWR_SETTINGS_PWM_OUT, 0xff);
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if (ret)
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goto err_mutex;
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}
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iqs620_pwm->out_en = state->enabled;
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err_mutex:
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mutex_unlock(&iqs620_pwm->lock);
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mutex_unlock(&iqs620_pwm->lock);
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return ret;
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return ret;
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@ -121,12 +116,11 @@ static void iqs620_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
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/*
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/*
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* Since the device cannot generate a 0% duty cycle, requests to do so
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* Since the device cannot generate a 0% duty cycle, requests to do so
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* cause subsequent calls to iqs620_pwm_get_state to report the output
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* cause subsequent calls to iqs620_pwm_get_state to report the output
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* as disabled with duty cycle equal to that which was in use prior to
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* as disabled. This is not ideal, but is the best compromise based on
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* the request. This is not ideal, but is the best compromise based on
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* the capabilities of the device.
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* the capabilities of the device.
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*/
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*/
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state->enabled = iqs620_pwm->out_en;
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state->enabled = iqs620_pwm->duty_scale > 0;
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state->duty_cycle = DIV_ROUND_UP((iqs620_pwm->duty_val + 1) *
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state->duty_cycle = DIV_ROUND_UP(iqs620_pwm->duty_scale *
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IQS620_PWM_PERIOD_NS, 256);
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IQS620_PWM_PERIOD_NS, 256);
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mutex_unlock(&iqs620_pwm->lock);
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mutex_unlock(&iqs620_pwm->lock);
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@ -138,7 +132,6 @@ static int iqs620_pwm_notifier(struct notifier_block *notifier,
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unsigned long event_flags, void *context)
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unsigned long event_flags, void *context)
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{
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{
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struct iqs620_pwm_private *iqs620_pwm;
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struct iqs620_pwm_private *iqs620_pwm;
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struct iqs62x_core *iqs62x;
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int ret;
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int ret;
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if (!(event_flags & BIT(IQS62X_EVENT_SYS_RESET)))
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if (!(event_flags & BIT(IQS62X_EVENT_SYS_RESET)))
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@ -146,7 +139,6 @@ static int iqs620_pwm_notifier(struct notifier_block *notifier,
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iqs620_pwm = container_of(notifier, struct iqs620_pwm_private,
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iqs620_pwm = container_of(notifier, struct iqs620_pwm_private,
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notifier);
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notifier);
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iqs62x = iqs620_pwm->iqs62x;
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mutex_lock(&iqs620_pwm->lock);
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mutex_lock(&iqs620_pwm->lock);
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@ -155,16 +147,8 @@ static int iqs620_pwm_notifier(struct notifier_block *notifier,
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* of a device reset, so nothing else is printed here unless there is
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* of a device reset, so nothing else is printed here unless there is
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* an additional failure.
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* an additional failure.
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*/
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*/
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ret = regmap_write(iqs62x->regmap, IQS620_PWM_DUTY_CYCLE,
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ret = iqs620_pwm_init(iqs620_pwm, iqs620_pwm->duty_scale);
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iqs620_pwm->duty_val);
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if (ret)
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goto err_mutex;
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ret = regmap_update_bits(iqs62x->regmap, IQS620_PWR_SETTINGS,
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IQS620_PWR_SETTINGS_PWM_OUT,
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iqs620_pwm->out_en ? 0xff : 0);
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err_mutex:
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mutex_unlock(&iqs620_pwm->lock);
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mutex_unlock(&iqs620_pwm->lock);
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if (ret) {
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if (ret) {
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@ -211,12 +195,14 @@ static int iqs620_pwm_probe(struct platform_device *pdev)
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ret = regmap_read(iqs62x->regmap, IQS620_PWR_SETTINGS, &val);
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ret = regmap_read(iqs62x->regmap, IQS620_PWR_SETTINGS, &val);
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if (ret)
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if (ret)
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return ret;
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return ret;
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iqs620_pwm->out_en = val & IQS620_PWR_SETTINGS_PWM_OUT;
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ret = regmap_read(iqs62x->regmap, IQS620_PWM_DUTY_CYCLE, &val);
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if (val & IQS620_PWR_SETTINGS_PWM_OUT) {
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if (ret)
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ret = regmap_read(iqs62x->regmap, IQS620_PWM_DUTY_CYCLE, &val);
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return ret;
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if (ret)
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iqs620_pwm->duty_val = val;
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return ret;
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iqs620_pwm->duty_scale = val + 1;
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}
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iqs620_pwm->chip.dev = &pdev->dev;
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iqs620_pwm->chip.dev = &pdev->dev;
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iqs620_pwm->chip.ops = &iqs620_pwm_ops;
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iqs620_pwm->chip.ops = &iqs620_pwm_ops;
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