Messages in this thread | | | From | Sven Van Asbroeck <> | Date | Wed, 16 Dec 2020 23:02:03 -0500 | Subject | Re: [PATCH v5 4/7] pwm: pca9685: Reset registers to POR state in probe |
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Hi Clemens, minor nit below.
On Wed, Dec 16, 2020 at 7:53 AM Clemens Gruber <clemens.gruber@pqgruber.com> wrote: > > Reset the prescale and ON/OFF registers to their POR default state in > the probe function. Otherwise, the PWMs could still be active after a > watchdog reset and reboot, etc. > > Signed-off-by: Clemens Gruber <clemens.gruber@pqgruber.com> > --- > drivers/pwm/pwm-pca9685.c | 9 +++++++-- > 1 file changed, 7 insertions(+), 2 deletions(-) > > diff --git a/drivers/pwm/pwm-pca9685.c b/drivers/pwm/pwm-pca9685.c > index 7b14447f3c05..38aadaf50996 100644 > --- a/drivers/pwm/pwm-pca9685.c > +++ b/drivers/pwm/pwm-pca9685.c > @@ -47,6 +47,7 @@ > #define PCA9685_ALL_LED_OFF_H 0xFD > #define PCA9685_PRESCALE 0xFE > > +#define PCA9685_PRESCALE_DEF 0x1E /* => default frequency of ~200 Hz */ > #define PCA9685_PRESCALE_MIN 0x03 /* => max. frequency of 1526 Hz */ > #define PCA9685_PRESCALE_MAX 0xFF /* => min. frequency of 24 Hz */ > > @@ -446,9 +447,11 @@ static int pca9685_pwm_probe(struct i2c_client *client, > reg &= ~(MODE1_ALLCALL | MODE1_SUB1 | MODE1_SUB2 | MODE1_SUB3); > regmap_write(pca->regmap, PCA9685_MODE1, reg); > > - /* Clear all "full off" bits */ > + /* Reset ON/OFF registers to HW defaults (only full OFF bit is set) */ > + regmap_write(pca->regmap, PCA9685_ALL_LED_ON_L, 0); > + regmap_write(pca->regmap, PCA9685_ALL_LED_ON_H, 0); > regmap_write(pca->regmap, PCA9685_ALL_LED_OFF_L, 0); > - regmap_write(pca->regmap, PCA9685_ALL_LED_OFF_H, 0); > + regmap_write(pca->regmap, PCA9685_ALL_LED_OFF_H, LED_FULL); > > pca->chip.ops = &pca9685_pwm_ops; > /* Add an extra channel for ALL_LED */ > @@ -470,8 +473,10 @@ static int pca9685_pwm_probe(struct i2c_client *client, > /* > * The chip comes out of power-up in the sleep state, > * but force it to sleep in case it was woken up before > + * and set the default prescale value > */ > pca9685_set_sleep_mode(pca, true); > + regmap_write(pca->regmap, PCA9685_PRESCALE, PCA9685_PRESCALE_DEF); > pm_runtime_set_suspended(&client->dev); > pm_runtime_enable(&client->dev);
Consider making it clearer that prescale can only be touched when the chip is in sleep mode. Suggestion:
/* set the default prescale value - chip _must_ be in sleep mode */ regmap_write(pca->regmap, PCA9685_PRESCALE, PCA9685_PRESCALE_DEF);
> > -- > 2.29.2 >
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