Re: [PATCH v3 09/15] pwm: crc: Enable/disable PWM output on enable/disable

["Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>]

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Hello,

On Sat, Jun 20, 2020 at 02:17:52PM +0200, Hans de Goede wrote:
> The pwm-crc code is using 2 different enable bits:
> 1. bit 7 of the PWM0_CLK_DIV (PWM_OUTPUT_ENABLE)
> 2. bit 0 of the BACKLIGHT_EN register
> 
> So far we've kept the PWM_OUTPUT_ENABLE bit set when disabling the PWM,
> this commit makes crc_pwm_disable() clear it on disable and makes
> crc_pwm_enable() set it again on re-enable.
> 
> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
> ---
> Changes in v3:
> - Remove paragraph about tri-stating the output from the commit message,
>   we don't have a datasheet so this was just an unfounded guess
> ---
>  drivers/pwm/pwm-crc.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/pwm/pwm-crc.c b/drivers/pwm/pwm-crc.c
> index 81232da0c767..b72008c9b072 100644
> --- a/drivers/pwm/pwm-crc.c
> +++ b/drivers/pwm/pwm-crc.c
> @@ -54,7 +54,9 @@ static int crc_pwm_calc_clk_div(int period_ns)
>  static int crc_pwm_enable(struct pwm_chip *c, struct pwm_device *pwm)
>  {
>  	struct crystalcove_pwm *crc_pwm = to_crc_pwm(c);
> +	int div = crc_pwm_calc_clk_div(pwm_get_period(pwm));
>  
> +	regmap_write(crc_pwm->regmap, PWM0_CLK_DIV, div | PWM_OUTPUT_ENABLE);
>  	regmap_write(crc_pwm->regmap, BACKLIGHT_EN, 1);
>  
>  	return 0;
> @@ -63,8 +65,10 @@ static int crc_pwm_enable(struct pwm_chip *c, struct pwm_device *pwm)
>  static void crc_pwm_disable(struct pwm_chip *c, struct pwm_device *pwm)
>  {
>  	struct crystalcove_pwm *crc_pwm = to_crc_pwm(c);
> +	int div = crc_pwm_calc_clk_div(pwm_get_period(pwm));
>  
>  	regmap_write(crc_pwm->regmap, BACKLIGHT_EN, 0);
> +	regmap_write(crc_pwm->regmap, PWM0_CLK_DIV, div);
>  }
>  
>  static int crc_pwm_config(struct pwm_chip *c, struct pwm_device *pwm,

In the absence of documentation this looks reasonable.

Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

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