Re: [PATCH v4 1/4] pwm: pca9685: Switch to atomic API

[Clemens Gruber]

Hi Sven,

On Mon, Dec 07, 2020 at 06:22:08PM -0500, Sven Van Asbroeck wrote:
> Hi Clemens, see below.
> 
> On Mon, Dec 7, 2020 at 2:37 PM Clemens Gruber
> <clemens.gruber@xxxxxxxxxxxx> wrote:
> >
> > The switch to the atomic API goes hand in hand with a few fixes to
> > previously experienced issues:
> > - The duty cycle is no longer lost after disable/enable (previously the
> >   OFF registers were cleared in disable and the user was required to
> >   call config to restore the duty cycle settings)
> > - If one sets a period resulting in the same prescale register value,
> >   the sleep and write to the register is now skipped
> > - The prescale register is now set to the default value in probe. On
> >   systems without CONFIG_PM, the chip is woken up at probe time.
> >
> > The hardware readout may return slightly different values than those
> > that were set in apply due to the limited range of possible prescale and
> > counter register values. If one channel is reconfigured with new duty
> > cycle and period, the others will keep the same relative duty cycle to
> > period ratio as they had before, even though the per-chip / global
> > frequency changed. (The PCA9685 has only one prescaler!)
> >
> > Note that although the datasheet mentions 200 Hz as default frequency
> > when using the internal 25 MHz oscillator, the calculated period from
> > the default prescaler register setting of 30 is 5079040ns.
> >
> > Signed-off-by: Clemens Gruber <clemens.gruber@xxxxxxxxxxxx>
> > ---
> > Changes since v3:
> > - Refactoring: Extracted common functions
> > - Read prescale register value instead of caching it
> > - Return all zeros and disabled for "all LEDs" channel state
> > - Improved duty calculation / mapping to 0..4096
> >
> > Changes since v2:
> > - Always set default prescale value in probe
> > - Simplified probe code
> > - Inlined functions with one callsite
> >
> > Changes since v1:
> > - Fixed a logic error
> > - Impoved PM runtime handling and fixed !CONFIG_PM
> > - Write default prescale reg value if invalid in probe
> > - Reuse full_off/_on functions throughout driver
> > - Use cached prescale value whenever possible
> >
> >  drivers/pwm/pwm-pca9685.c | 335 ++++++++++++++++++++------------------
> >  1 file changed, 175 insertions(+), 160 deletions(-)
> >
> > diff --git a/drivers/pwm/pwm-pca9685.c b/drivers/pwm/pwm-pca9685.c
> > index 4a55dc18656c..0425e0bcb81e 100644
> > --- a/drivers/pwm/pwm-pca9685.c
> > +++ b/drivers/pwm/pwm-pca9685.c
> > @@ -47,11 +47,11 @@
> >  #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 */
> >
> >  #define PCA9685_COUNTER_RANGE  4096
> > -#define PCA9685_DEFAULT_PERIOD 5000000 /* Default period_ns = 1/200 Hz */
> >  #define PCA9685_OSC_CLOCK_MHZ  25      /* Internal oscillator with 25 MHz */
> >
> >  #define PCA9685_NUMREGS                0xFF
> > @@ -74,7 +74,6 @@
> >  struct pca9685 {
> >         struct pwm_chip chip;
> >         struct regmap *regmap;
> > -       int period_ns;
> >  #if IS_ENABLED(CONFIG_GPIOLIB)
> >         struct mutex lock;
> >         struct gpio_chip gpio;
> > @@ -87,6 +86,81 @@ static inline struct pca9685 *to_pca(struct pwm_chip *chip)
> >         return container_of(chip, struct pca9685, chip);
> >  }
> >
> > +static void pca9685_pwm_set_full_off(struct pca9685 *pca, int index, bool enable)
> > +{
> > +       unsigned int val = enable ? LED_FULL : 0;
> > +
> > +       /* Note: The full OFF bit has the highest precedence */
> > +
> > +       if (index >= PCA9685_MAXCHAN) {
> > +               regmap_write(pca->regmap, PCA9685_ALL_LED_OFF_H, val);
> > +               return;
> > +       }
> > +       regmap_update_bits(pca->regmap, LED_N_OFF_H(index), LED_FULL, val);
> > +}
> > +
> > +static bool pca9685_pwm_is_full_off(struct pca9685 *pca, int index)
> > +{
> > +       unsigned int val = 0;
> > +
> > +       if (index >= PCA9685_MAXCHAN)
> > +               return false;
> > +
> > +       regmap_read(pca->regmap, LED_N_OFF_H(index), &val);
> > +       return val & LED_FULL;
> > +}
> > +
> > +static void pca9685_pwm_set_full_on(struct pca9685 *pca, int index, bool enable)
> > +{
> > +       unsigned int val = enable ? LED_FULL : 0;
> > +
> > +       if (index >= PCA9685_MAXCHAN) {
> > +               regmap_write(pca->regmap, PCA9685_ALL_LED_ON_H, val);
> > +               return;
> > +       }
> > +       regmap_update_bits(pca->regmap, LED_N_ON_H(index), LED_FULL, val);
> > +}
> 
> If the "full off" bit is set, calling pwm_set_full_on(pca, index, true)
> won't actually bring the led full on, correct ?

Correct. Although I added a comment in pwm_set_full_off to explain that
the full OFF bit has precedence and we are (un)setting the full OFF bit
when necessary, I agree that this can and should be improved to be less
confusing.

> 
> This can be very confusing. See below for a suggestion to make this clearer.
> 
> > +
> > +static bool pca9685_pwm_is_full_on(struct pca9685 *pca, int index)
> > +{
> > +       unsigned int val = 0;
> > +
> > +       if (index >= PCA9685_MAXCHAN)
> > +               return false;
> > +
> > +       regmap_read(pca->regmap, LED_N_ON_H(index), &val);
> > +       return val & LED_FULL;
> > +}
> > +
> > +static void pca9685_pwm_set_off_time(struct pca9685 *pca, int index, unsigned int off)
> > +{
> > +       int reg;
> > +
> > +       /* Note: This function also clears the full OFF bit */
> > +
> > +       reg = index >= PCA9685_MAXCHAN ?
> > +               PCA9685_ALL_LED_OFF_L : LED_N_OFF_L(index);
> > +       regmap_write(pca->regmap, reg, off & 0xff);
> > +
> > +       reg = index >= PCA9685_MAXCHAN ?
> > +               PCA9685_ALL_LED_OFF_H : LED_N_OFF_H(index);
> > +       regmap_write(pca->regmap, reg, (off >> 8) & 0xf);
> > +}
> > +
> > +static unsigned int pca9685_pwm_off_time(struct pca9685 *pca, int index)
> > +{
> > +       unsigned int off, val = 0;
> > +
> > +       if (index >= PCA9685_MAXCHAN)
> > +               return 0;
> > +
> > +       regmap_read(pca->regmap, LED_N_OFF_H(index), &val);
> > +       off = (val & 0xf) << 8;
> > +
> > +       regmap_read(pca->regmap, LED_N_OFF_L(index), &val);
> > +       return off | (val & 0xff);
> > +}
> > +
> >  #if IS_ENABLED(CONFIG_GPIOLIB)
> >  static bool pca9685_pwm_test_and_set_inuse(struct pca9685 *pca, int pwm_idx)
> >  {
> > @@ -138,34 +212,31 @@ static int pca9685_pwm_gpio_request(struct gpio_chip *gpio, unsigned int offset)
> >  static int pca9685_pwm_gpio_get(struct gpio_chip *gpio, unsigned int offset)
> >  {
> >         struct pca9685 *pca = gpiochip_get_data(gpio);
> > -       struct pwm_device *pwm = &pca->chip.pwms[offset];
> > -       unsigned int value;
> > -
> > -       regmap_read(pca->regmap, LED_N_ON_H(pwm->hwpwm), &value);
> >
> > -       return value & LED_FULL;
> > +       return !pca9685_pwm_is_full_off(pca, offset);
> >  }
> >
> >  static void pca9685_pwm_gpio_set(struct gpio_chip *gpio, unsigned int offset,
> >                                  int value)
> >  {
> >         struct pca9685 *pca = gpiochip_get_data(gpio);
> > -       struct pwm_device *pwm = &pca->chip.pwms[offset];
> > -       unsigned int on = value ? LED_FULL : 0;
> > -
> > -       /* Clear both OFF registers */
> > -       regmap_write(pca->regmap, LED_N_OFF_L(pwm->hwpwm), 0);
> > -       regmap_write(pca->regmap, LED_N_OFF_H(pwm->hwpwm), 0);
> >
> > -       /* Set the full ON bit */
> > -       regmap_write(pca->regmap, LED_N_ON_H(pwm->hwpwm), on);
> > +       if (value) {
> > +               pca9685_pwm_set_full_on(pca, offset, true);
> > +               /* Clear full OFF bit last */
> > +               pca9685_pwm_set_full_off(pca, offset, false);
> > +       } else {
> > +               /* Set full OFF bit first */
> > +               pca9685_pwm_set_full_off(pca, offset, true);
> > +               pca9685_pwm_set_full_on(pca, offset, false);
> > +       }
> >  }
> >
> >  static void pca9685_pwm_gpio_free(struct gpio_chip *gpio, unsigned int offset)
> >  {
> >         struct pca9685 *pca = gpiochip_get_data(gpio);
> >
> > -       pca9685_pwm_gpio_set(gpio, offset, 0);
> > +       pca9685_pwm_set_full_off(pca, offset, true);
> >         pm_runtime_put(pca->chip.dev);
> >         pca9685_pwm_clear_inuse(pca, offset);
> >  }
> > @@ -246,165 +317,98 @@ static void pca9685_set_sleep_mode(struct pca9685 *pca, bool enable)
> >         }
> >  }
> >
> > -static int pca9685_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
> > -                             int duty_ns, int period_ns)
> > +static void pca9685_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
> > +                                 struct pwm_state *state)
> >  {
> >         struct pca9685 *pca = to_pca(chip);
> >         unsigned long long duty;
> > -       unsigned int reg;
> > -       int prescale;
> > -
> > -       if (period_ns != pca->period_ns) {
> > -               prescale = DIV_ROUND_CLOSEST(PCA9685_OSC_CLOCK_MHZ * period_ns,
> > -                                            PCA9685_COUNTER_RANGE * 1000) - 1;
> > -
> > -               if (prescale >= PCA9685_PRESCALE_MIN &&
> > -                       prescale <= PCA9685_PRESCALE_MAX) {
> > -                       /*
> > -                        * Putting the chip briefly into SLEEP mode
> > -                        * at this point won't interfere with the
> > -                        * pm_runtime framework, because the pm_runtime
> > -                        * state is guaranteed active here.
> > -                        */
> > -                       /* Put chip into sleep mode */
> > -                       pca9685_set_sleep_mode(pca, true);
> > -
> > -                       /* Change the chip-wide output frequency */
> > -                       regmap_write(pca->regmap, PCA9685_PRESCALE, prescale);
> > -
> > -                       /* Wake the chip up */
> > -                       pca9685_set_sleep_mode(pca, false);
> > -
> > -                       pca->period_ns = period_ns;
> > -               } else {
> > -                       dev_err(chip->dev,
> > -                               "prescaler not set: period out of bounds!\n");
> > -                       return -EINVAL;
> > -               }
> > -       }
> > +       unsigned int val = 0;
> >
> > -       if (duty_ns < 1) {
> > -               if (pwm->hwpwm >= PCA9685_MAXCHAN)
> > -                       reg = PCA9685_ALL_LED_OFF_H;
> > -               else
> > -                       reg = LED_N_OFF_H(pwm->hwpwm);
> > +       /* Calculate (chip-wide) period from prescale value */
> > +       regmap_read(pca->regmap, PCA9685_PRESCALE, &val);
> > +       state->period = (PCA9685_COUNTER_RANGE * 1000 / PCA9685_OSC_CLOCK_MHZ) *
> > +                       (val + 1);
> >
> > -               regmap_write(pca->regmap, reg, LED_FULL);
> > +       /* The (per-channel) polarity is fixed */
> > +       state->polarity = PWM_POLARITY_NORMAL;
> >
> > -               return 0;
> > +       if (pwm->hwpwm >= PCA9685_MAXCHAN) {
> > +               /*
> > +                * The "all LEDs" channel does not support HW readout
> > +                * Return 0 and disabled for backwards compatibility
> > +                */
> > +               state->duty_cycle = 0;
> > +               state->enabled = false;
> > +               return;
> >         }
> >
> > -       if (duty_ns == period_ns) {
> > -               /* Clear both OFF registers */
> > -               if (pwm->hwpwm >= PCA9685_MAXCHAN)
> > -                       reg = PCA9685_ALL_LED_OFF_L;
> > -               else
> > -                       reg = LED_N_OFF_L(pwm->hwpwm);
> > -
> > -               regmap_write(pca->regmap, reg, 0x0);
> > -
> > -               if (pwm->hwpwm >= PCA9685_MAXCHAN)
> > -                       reg = PCA9685_ALL_LED_OFF_H;
> > -               else
> > -                       reg = LED_N_OFF_H(pwm->hwpwm);
> > -
> > -               regmap_write(pca->regmap, reg, 0x0);
> > -
> > -               /* Set the full ON bit */
> > -               if (pwm->hwpwm >= PCA9685_MAXCHAN)
> > -                       reg = PCA9685_ALL_LED_ON_H;
> > -               else
> > -                       reg = LED_N_ON_H(pwm->hwpwm);
> > +       state->enabled = !pca9685_pwm_is_full_off(pca, pwm->hwpwm);
> >
> > -               regmap_write(pca->regmap, reg, LED_FULL);
> > -
> > -               return 0;
> > +       if (state->enabled && pca9685_pwm_is_full_on(pca, pwm->hwpwm)) {
> > +               state->duty_cycle = state->period;
> > +               return;
> >         }
> >
> > -       duty = PCA9685_COUNTER_RANGE * (unsigned long long)duty_ns;
> > -       duty = DIV_ROUND_UP_ULL(duty, period_ns);
> > -
> > -       if (pwm->hwpwm >= PCA9685_MAXCHAN)
> > -               reg = PCA9685_ALL_LED_OFF_L;
> > -       else
> > -               reg = LED_N_OFF_L(pwm->hwpwm);
> > -
> > -       regmap_write(pca->regmap, reg, (int)duty & 0xff);
> > -
> > -       if (pwm->hwpwm >= PCA9685_MAXCHAN)
> > -               reg = PCA9685_ALL_LED_OFF_H;
> > -       else
> > -               reg = LED_N_OFF_H(pwm->hwpwm);
> > -
> > -       regmap_write(pca->regmap, reg, ((int)duty >> 8) & 0xf);
> > -
> > -       /* Clear the full ON bit, otherwise the set OFF time has no effect */
> > -       if (pwm->hwpwm >= PCA9685_MAXCHAN)
> > -               reg = PCA9685_ALL_LED_ON_H;
> > -       else
> > -               reg = LED_N_ON_H(pwm->hwpwm);
> > -
> > -       regmap_write(pca->regmap, reg, 0);
> > -
> > -       return 0;
> > +       duty = pca9685_pwm_off_time(pca, pwm->hwpwm) * state->period;
> > +       state->duty_cycle = duty / PCA9685_COUNTER_RANGE;
> >  }
> >
> > -static int pca9685_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
> > +static int pca9685_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
> > +                            const struct pwm_state *state)
> >  {
> >         struct pca9685 *pca = to_pca(chip);
> > -       unsigned int reg;
> > -
> > -       /*
> > -        * The PWM subsystem does not support a pre-delay.
> > -        * So, set the ON-timeout to 0
> > -        */
> > -       if (pwm->hwpwm >= PCA9685_MAXCHAN)
> > -               reg = PCA9685_ALL_LED_ON_L;
> > -       else
> > -               reg = LED_N_ON_L(pwm->hwpwm);
> > +       unsigned long long duty, prescale;
> > +       unsigned int val = 0;
> >
> > -       regmap_write(pca->regmap, reg, 0);
> > +       if (state->polarity != PWM_POLARITY_NORMAL)
> > +               return -EOPNOTSUPP;
> >
> > -       if (pwm->hwpwm >= PCA9685_MAXCHAN)
> > -               reg = PCA9685_ALL_LED_ON_H;
> > -       else
> > -               reg = LED_N_ON_H(pwm->hwpwm);
> > -
> > -       regmap_write(pca->regmap, reg, 0);
> > -
> > -       /*
> > -        * Clear the full-off bit.
> > -        * It has precedence over the others and must be off.
> > -        */
> > -       if (pwm->hwpwm >= PCA9685_MAXCHAN)
> > -               reg = PCA9685_ALL_LED_OFF_H;
> > -       else
> > -               reg = LED_N_OFF_H(pwm->hwpwm);
> > +       prescale = DIV_ROUND_CLOSEST_ULL(PCA9685_OSC_CLOCK_MHZ * state->period,
> > +                                        PCA9685_COUNTER_RANGE * 1000) - 1;
> > +       if (prescale < PCA9685_PRESCALE_MIN || prescale > PCA9685_PRESCALE_MAX) {
> > +               dev_err(chip->dev, "prescaler not set: period out of bounds!\n");
> > +               return -EINVAL;
> > +       }
> >
> > -       regmap_update_bits(pca->regmap, reg, LED_FULL, 0x0);
> > +       regmap_read(pca->regmap, PCA9685_PRESCALE, &val);
> > +       if (prescale != val) {
> > +               /*
> > +                * Putting the chip briefly into SLEEP mode
> > +                * at this point won't interfere with the
> > +                * pm_runtime framework, because the pm_runtime
> > +                * state is guaranteed active here.
> > +                */
> > +               /* Put chip into sleep mode */
> > +               pca9685_set_sleep_mode(pca, true);
> >
> > -       return 0;
> > -}
> > +               /* Change the chip-wide output frequency */
> > +               regmap_write(pca->regmap, PCA9685_PRESCALE, (int)prescale);
> >
> > -static void pca9685_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
> > -{
> > -       struct pca9685 *pca = to_pca(chip);
> > -       unsigned int reg;
> > +               /* Wake the chip up */
> > +               pca9685_set_sleep_mode(pca, false);
> > +       }
> >
> > -       if (pwm->hwpwm >= PCA9685_MAXCHAN)
> > -               reg = PCA9685_ALL_LED_OFF_H;
> > -       else
> > -               reg = LED_N_OFF_H(pwm->hwpwm);
> > +       duty = PCA9685_COUNTER_RANGE * state->duty_cycle;
> > +       duty = DIV_ROUND_CLOSEST_ULL(duty, state->period);
> >
> > -       regmap_write(pca->regmap, reg, LED_FULL);
> > +       if (!state->enabled || duty < 1) {
> > +               /* Set full OFF bit first */
> > +               pca9685_pwm_set_full_off(pca, pwm->hwpwm, true);
> > +               pca9685_pwm_set_full_on(pca, pwm->hwpwm, false);
> > +               return 0;
> > +       }
> >
> > -       /* Clear the LED_OFF counter. */
> > -       if (pwm->hwpwm >= PCA9685_MAXCHAN)
> > -               reg = PCA9685_ALL_LED_OFF_L;
> > -       else
> > -               reg = LED_N_OFF_L(pwm->hwpwm);
> > +       if (duty == PCA9685_COUNTER_RANGE) {
> > +               pca9685_pwm_set_full_on(pca, pwm->hwpwm, true);
> > +               /* Clear full OFF bit last */
> > +               pca9685_pwm_set_full_off(pca, pwm->hwpwm, false);
> 
> I think "this bit first, this bit last" can be confusing and fragile.
> It is also repeated in a few different places.
> Suggestion on how to improve this, below.

I wanted to let people know that the order is important, but yes, it is
also a little confusing.

> 
> > +               return 0;
> > +       }
> >
> > -       regmap_write(pca->regmap, reg, 0x0);
> > +       pca9685_pwm_set_off_time(pca, pwm->hwpwm, duty);
> > +       /* Clear full ON bit after OFF time was set */
> > +       pca9685_pwm_set_full_on(pca, pwm->hwpwm, false);
> > +       return 0;
> >  }
> 
> I think pwm_apply() is broken in the following scenario:
> 
> 1. pwm_apply(enable=false)
> 2. pwm_apply(enable=true, duty_cycle=50%, period=200Hz)
> 3. result: pwm still full off (disabled)

No, this works correctly. I'll explain below.

> 
> and that is because pwm_apply() clears the "full off" bit only when the user
> requests "full on".

The full OFF bit is cleared in pca9685_pwm_set_off_time.
I did add a comment in that function that mentions it, but this can be
easily overlooked and is not clear from the name, so also something that
can and should be improved.

> 
> I attribute this to the confusing nature of this chip. It's hard to keep the
> chip's complete state fully in one's head.

I agree, you always have to think about the chip's internals. The
abstractions / common functions should contain the internals as
implementation details, so we do not have to think about them every time
we use on of these functions.

> One possible way to keep this manageable is by writing the functions in terms of
> *led state* and not in terms of the *bits* it sets:
> 
> - set_full_on() should make the led go full on. So it sets "full on"
>   and clears "full off" bits.
> - set_full_off() should make the led go full off. So it sets the "full off" bit.
> - set_duty() brings the led into duty mode. So it should clear "full off",
>   clear "full on", and write the on/off times.
> 
> And actually, all that's needed is a single function, because duty == 0 means
> "full off" and duty == 4095 means "full on".

Interesting! I'll have to think this through tomorrow but I think it
could work. I will wait with the next revision until we decide what to
do about Uwe's suggestion and then send a v5.

> 
> Example in pseudo code:
> 
> static void pca9685_pwm_set_duty(struct pca9685 *pca, int index,
> unsigned int duty)
> {
>     if (duty == 0) {
>         /* full off takes precedence */
>         regmap_write(full_off(index), ON);
>     } else if (duty >= (COUNTER_RANGE - 1)) {
>         regmap_write(full_on(index), ON);
>         regmap_write(full_off(index), OFF);
>     } else {
>         regmap_write(off_time(index), duty);
>         regmap_write(full_on(index), OFF);
>         regmap_write(full_off(index), OFF);
>     }
> }
> 
> static unsigned int pca9685_pwm_get_duty(struct pca9685 *pca, int index)
> {
>     if (WARN_ON(index >= PCA9685_MAXCHAN)) {
>         /* register not readable, should never happen */
>         return 0;
>     }
>     if (full_off(index) is ON)
>         return 0;
>     else if (full_on(index) is ON)
>         return COUNTER_RANGE - 1;
>     return off_time(index);
> }
> 
> I suspect that once all on/off register accesses go through these two functions,
> things will look simpler and there will be less risk of getting it wrong.
> 
> To prevent a forest of "index >= PCA9685_MAXCHAN" checks, I suggest creating
> an helper function or macro, e.g.
> 
> static unsigned int led_off_h(int index)
> {
>     return (index >= PCA9685_MAXCHAN) ? PCA9685_ALL_LED_OFF_H :
> LED_N_OFF_H(index);
> }
> 
> then setting a register looks simple:
> regmap_write(pca->regmap, led_off_h(index), LED_FULL);
> 
> >
> >  static int pca9685_pwm_request(struct pwm_chip *chip, struct pwm_device *pwm)
> > @@ -422,15 +426,14 @@ static void pca9685_pwm_free(struct pwm_chip *chip, struct pwm_device *pwm)
> >  {
> >         struct pca9685 *pca = to_pca(chip);
> >
> > -       pca9685_pwm_disable(chip, pwm);
> > +       pca9685_pwm_set_full_off(pca, pwm->hwpwm, true);
> >         pm_runtime_put(chip->dev);
> >         pca9685_pwm_clear_inuse(pca, pwm->hwpwm);
> >  }
> >
> >  static const struct pwm_ops pca9685_pwm_ops = {
> > -       .enable = pca9685_pwm_enable,
> > -       .disable = pca9685_pwm_disable,
> > -       .config = pca9685_pwm_config,
> > +       .get_state = pca9685_pwm_get_state,
> > +       .apply = pca9685_pwm_apply,
> >         .request = pca9685_pwm_request,
> >         .free = pca9685_pwm_free,
> >         .owner = THIS_MODULE,
> > @@ -461,7 +464,6 @@ static int pca9685_pwm_probe(struct i2c_client *client,
> >                         ret);
> >                 return ret;
> >         }
> > -       pca->period_ns = PCA9685_DEFAULT_PERIOD;
> >
> >         i2c_set_clientdata(client, pca);
> >
> > @@ -505,14 +507,20 @@ static int pca9685_pwm_probe(struct i2c_client *client,
> >                 return ret;
> >         }
> >
> > -       /* The chip comes out of power-up in the active state */
> > -       pm_runtime_set_active(&client->dev);
> >         /*
> > -        * Enable will put the chip into suspend, which is what we
> > -        * want as all outputs are disabled at this point
> > +        * Always initialize with default prescale, but chip must be
> > +        * in sleep mode while changing prescaler.
> >          */
> > +       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);
> >
> > +       if (!IS_ENABLED(CONFIG_PM)) {
> > +               /* Wake the chip up on non-PM environments */
> > +               pca9685_set_sleep_mode(pca, false);
> > +       }
> > +
> >         return 0;
> >  }
> >
> > @@ -524,7 +532,14 @@ static int pca9685_pwm_remove(struct i2c_client *client)
> >         ret = pwmchip_remove(&pca->chip);
> >         if (ret)
> >                 return ret;
> > +
> >         pm_runtime_disable(&client->dev);
> > +
> > +       if (!IS_ENABLED(CONFIG_PM)) {
> > +               /* Put chip in sleep state on non-PM environments */
> > +               pca9685_set_sleep_mode(pca, true);
> > +       }
> > +
> >         return 0;
> >  }
> >
> > --
> > 2.29.2
> >

Thanks,
Clemens