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authorJeff LaBundy <jeff@labundy.com>2021-01-18 22:30:29 -0600
committerThierry Reding <thierry.reding@gmail.com>2021-02-22 15:18:50 +0100
commit28208c7b4a2c38ea91b6ee04f6023d3145257f5d (patch)
tree3b7f44b5dc811fe3931bb4ef54ac18122bcd0166 /drivers/pwm
parent72d6b2459dbd539c1369149e501fdc3dc8ddef16 (diff)
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-K├Ânig <u.kleine-koenig@pengutronix.de> Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
Diffstat (limited to 'drivers/pwm')
-rw-r--r--drivers/pwm/pwm-iqs620a.c88
1 files changed, 37 insertions, 51 deletions
diff --git a/drivers/pwm/pwm-iqs620a.c b/drivers/pwm/pwm-iqs620a.c
index 14b18fb4f527..957b972c458b 100644
--- a/drivers/pwm/pwm-iqs620a.c
+++ b/drivers/pwm/pwm-iqs620a.c
@@ -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;
- 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;
- }
-
- if (duty_scale) {
- u8 duty_val = duty_scale - 1;
+ if (!state->enabled)
+ duty_scale = 0;
- 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;
- }
+ mutex_lock(&iqs620_pwm->lock);
- iqs620_pwm->out_en = state->enabled;
+ ret = iqs620_pwm_init(iqs620_pwm, duty_scale);
+ if (!ret)
+ iqs620_pwm->duty_scale = duty_scale;
-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;