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

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@189.cn

I had another comment suggestion but you've been through enough. Thanks for working this to completion.

Reviewed-by: Alex Elder elder@linaro.org

---

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, };