Re: [PATCH v2] staging: greybus: introduce pwm_ops::apply

Greg KH
2022-02-22T13:49:16Z

On Tue, Feb 22, 2022 at 02:19:12PM +0800, Song Chen wrote:
> Hi Greg,
>
> 在 2022/2/22 01:06, Greg KH 写道:
> > On Fri, Feb 11, 2022 at 08:02:27PM +0800, Song Chen wrote:
> > > Introduce apply in pwm_ops to replace legacy operations,
> > > like enable, disable, config and set_polarity.
> > >
> > > Signed-off-by: Song Chen <chensong_2000@189.cn>
> > >
> > > ---
> > > 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.
> > > ---
> > > drivers/staging/greybus/pwm.c | 61 ++++++++++++-----------
> > > include/linux/greybus/greybus_protocols.h | 4 +-
> > > 2 files changed, 34 insertions(+), 31 deletions(-)
> > >
> > > diff --git a/drivers/staging/greybus/pwm.c b/drivers/staging/greybus/pwm.c
> > > index 891a6a672378..03c69db5b9be 100644
> > > --- a/drivers/staging/greybus/pwm.c
> > > +++ b/drivers/staging/greybus/pwm.c
> > > @@ -89,7 +89,7 @@ static int gb_pwm_deactivate_operation(struct gb_pwm_chip *pwmc,
> > > }
> > > static int gb_pwm_config_operation(struct gb_pwm_chip *pwmc,
> > > - u8 which, u32 duty, u32 period)
> > > + u8 which, u64 duty, u64 period)
> > > {
> > > struct gb_pwm_config_request request;
> > > struct gbphy_device *gbphy_dev;
> > > @@ -99,8 +99,8 @@ static int gb_pwm_config_operation(struct gb_pwm_chip *pwmc,
> > > return -EINVAL;
> > > request.which = which;
> > > - request.duty = cpu_to_le32(duty);
> > > - request.period = cpu_to_le32(period);
> > > + request.duty = duty;
> > > + request.period = period;
> > > gbphy_dev = to_gbphy_dev(pwmc->chip.dev);
> > > ret = gbphy_runtime_get_sync(gbphy_dev);
> > > @@ -204,43 +204,46 @@ 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;
> > > struct gb_pwm_chip *pwmc = pwm_chip_to_gb_pwm_chip(chip);
> > > - return gb_pwm_config_operation(pwmc, pwm->hwpwm, duty_ns, period_ns);
> > > -};
> > > -
> > > -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);
> > > -
> > > - return gb_pwm_set_polarity_operation(pwmc, pwm->hwpwm, polarity);
> > > -};
> > > + /* 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_enable(struct pwm_chip *chip, struct pwm_device *pwm)
> > > -{
> > > - 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_enable_operation(pwmc, pwm->hwpwm);
> > > -};
> > > + /* set period and duty cycle*/
> > > + err = gb_pwm_config_operation(pwmc, pwm->hwpwm, state->duty_cycle, state->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,
> > > };
> > > diff --git a/include/linux/greybus/greybus_protocols.h b/include/linux/greybus/greybus_protocols.h
> > > index aeb8f9243545..81a6f16de098 100644
> > > --- a/include/linux/greybus/greybus_protocols.h
> > > +++ b/include/linux/greybus/greybus_protocols.h
> > > @@ -812,8 +812,8 @@ struct gb_pwm_deactivate_request {
> > > struct gb_pwm_config_request {
> > > __u8 which;
> > > - __le32 duty;
> > > - __le32 period;
> > > + __u64 duty;
> > > + __u64 period;
> > > } __packed;
> >
> > Did you just change a greybus protocol message that is sent over the
> > wire? Why? And why drop the endian marking of it?
>
> I discussed with Uwe about losing bit and found there is no perfect way to
> avoid, even in Uwe's patch[1], as a result, we decided to widen duty and
> period in gb_pwm_config_request, the other side of the wire is supposed to
> change accordingly to support 64bit duty and period too(this will introduce
> compatibility problem and there is no variable like version to address it),
> similar with ktime_t in y2038, below is the detail [2]

Where are you changing the "other side of the wire" here? That wire is
in firmware, how are you going to coordinate that change?

This is a hardware API, you can not change it without a lot of very
careful work, and I still do not understand why it is needed. What
"problem" is this solving that requires the protocol to change?

thanks,

greg k-h