Re: [PATCH v6] staging: greybus: introduce pwm_ops::apply

[chensong <chensong_2000@xxxxxx>]

hi Alex,

On 2022/3/18 下午8:15, Alex Elder wrote:
> On 3/18/22 4:57 AM, Song Chen wrote:
> > Introduce newer .apply function in pwm_ops to replace legacy operations
> > including enable, disable, config and set_polarity.
> >
> > This guarantees atomic changes of the pwm controller configuration.
> >
> > Signed-off-by: Song Chen <chensong_2000@xxxxxx>
>
> I had another comment suggestion but you've been through enough.
> Thanks for working this to completion.

sorry about that, i probably missed it somehow. Thanks for the 
understanding.

Song

> Reviewed-by: Alex Elder <elder@xxxxxxxxxx>
>
> > ---
> > v2:
> > 1, define duty_cycle and period as u64 in gb_pwm_config_operation.
> > 2, define duty and period as u64 in gb_pwm_config_request.
> > 3, disable before configuring duty and period if the eventual goal
> >     is a disabled state.
> >
> > v3:
> > Regarding duty_cycle and period, I read more discussion in this thread,
> > min, warn or -EINVAL, seems no perfect way acceptable for everyone.
> > How about we limit their value to INT_MAX and throw a warning at the
> > same time when they are wrong?
> >
> > v4:
> > 1, explain why legacy operations are replaced.
> > 2, cap the value of period and duty to U32_MAX.
> >
> > v5:
> > 1, revise commit message.
> >
> > v6:
> > 1, revise commit message.
> > 2, explain why capping the value of period and duty to U32_MAX in
> >     comment.
> > ---
> >   drivers/staging/greybus/pwm.c | 64 ++++++++++++++++++++++-------------
> >   1 file changed, 40 insertions(+), 24 deletions(-)
> >
> > diff --git a/drivers/staging/greybus/pwm.c 
> > b/drivers/staging/greybus/pwm.c
> > index 891a6a672378..ad20ec24031e 100644
> > --- a/drivers/staging/greybus/pwm.c
> > +++ b/drivers/staging/greybus/pwm.c
> > @@ -204,43 +204,59 @@ static void gb_pwm_free(struct pwm_chip *chip, 
> > struct pwm_device *pwm)
> >       gb_pwm_deactivate_operation(pwmc, pwm->hwpwm);
> >   }
> > -static int gb_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
> > -             int duty_ns, int period_ns)
> > +static int gb_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
> > +            const struct pwm_state *state)
> >   {
> > +    int err;
> > +    bool enabled = pwm->state.enabled;
> > +    u64 period = state->period;
> > +    u64 duty_cycle = state->duty_cycle;
> >       struct gb_pwm_chip *pwmc = pwm_chip_to_gb_pwm_chip(chip);
> > -    return gb_pwm_config_operation(pwmc, pwm->hwpwm, duty_ns, 
> > period_ns);
> > -};
> > +    /* Set polarity */
> > +    if (state->polarity != pwm->state.polarity) {
> > +        if (enabled) {
> > +            gb_pwm_disable_operation(pwmc, pwm->hwpwm);
> > +            enabled = false;
> > +        }
> > +        err = gb_pwm_set_polarity_operation(pwmc, pwm->hwpwm, 
> > state->polarity);
> > +        if (err)
> > +            return err;
> > +    }
> > -static int gb_pwm_set_polarity(struct pwm_chip *chip, struct 
> > pwm_device *pwm,
> > -                   enum pwm_polarity polarity)
> > -{
> > -    struct gb_pwm_chip *pwmc = pwm_chip_to_gb_pwm_chip(chip);
> > +    if (!state->enabled) {
> > +        if (enabled)
> > +            gb_pwm_disable_operation(pwmc, pwm->hwpwm);
> > +        return 0;
> > +    }
> > -    return gb_pwm_set_polarity_operation(pwmc, pwm->hwpwm, polarity);
> > -};
> > +    /*
> > +     * Set period and duty cycle
> > +     *
> > +     * PWM privodes 64-bit period and duty_cycle, but greybus only 
> > accepts
> > +     * 32-bit, so their values have to be limited to U32_MAX.
> > +     */
> > +    if (period > U32_MAX)
> > +        period = U32_MAX;
> > -static int gb_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
> > -{
> > -    struct gb_pwm_chip *pwmc = pwm_chip_to_gb_pwm_chip(chip);
> > +    if (duty_cycle > period)
> > +        duty_cycle = period;
> > -    return gb_pwm_enable_operation(pwmc, pwm->hwpwm);
> > -};
> > +    err = gb_pwm_config_operation(pwmc, pwm->hwpwm, duty_cycle, period);
> > +    if (err)
> > +        return err;
> > -static void gb_pwm_disable(struct pwm_chip *chip, struct pwm_device 
> > *pwm)
> > -{
> > -    struct gb_pwm_chip *pwmc = pwm_chip_to_gb_pwm_chip(chip);
> > +    /* enable/disable */
> > +    if (!enabled)
> > +        return gb_pwm_enable_operation(pwmc, pwm->hwpwm);
> > -    gb_pwm_disable_operation(pwmc, pwm->hwpwm);
> > -};
> > +    return 0;
> > +}
> >   static const struct pwm_ops gb_pwm_ops = {
> >       .request = gb_pwm_request,
> >       .free = gb_pwm_free,
> > -    .config = gb_pwm_config,
> > -    .set_polarity = gb_pwm_set_polarity,
> > -    .enable = gb_pwm_enable,
> > -    .disable = gb_pwm_disable,
> > +    .apply = gb_pwm_apply,
> >       .owner = THIS_MODULE,
> >   };