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SubjectRe: [PATCH v2 3/6] pwm: mxs: add support for inverse polarity
On Fri, Oct 04, 2019 at 03:32:04PM +0200, Rasmus Villemoes wrote:
> If I'm reading of_pwm_xlate_with_flags() right, existing device trees
> that set #pwm-cells = 2 will continue to work.

Yes, that's what I expect, too.

> Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
> ---
> drivers/pwm/pwm-mxs.c | 14 ++++++++++----
> 1 file changed, 10 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/pwm/pwm-mxs.c b/drivers/pwm/pwm-mxs.c
> index 5a6835e18fc6..57562221c439 100644
> --- a/drivers/pwm/pwm-mxs.c
> +++ b/drivers/pwm/pwm-mxs.c
> @@ -25,8 +25,11 @@
> #define PERIOD_PERIOD(p) ((p) & 0xffff)
> #define PERIOD_PERIOD_MAX 0x10000
> #define PERIOD_ACTIVE_HIGH (3 << 16)
> +#define PERIOD_ACTIVE_LOW (2 << 16)
> +#define PERIOD_INACTIVE_HIGH (3 << 18)
> #define PERIOD_INACTIVE_LOW (2 << 18)
> #define PERIOD_POLARITY_NORMAL (PERIOD_ACTIVE_HIGH | PERIOD_INACTIVE_LOW)
> +#define PERIOD_POLARITY_INVERSE (PERIOD_ACTIVE_LOW | PERIOD_INACTIVE_HIGH)
> #define PERIOD_CDIV(div) (((div) & 0x7) << 20)
> #define PERIOD_CDIV_MAX 8
>
> @@ -50,9 +53,7 @@ static int mxs_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
> unsigned int period_cycles, duty_cycles;
> unsigned long rate;
> unsigned long long c;
> -
> - if (state->polarity != PWM_POLARITY_NORMAL)
> - return -ENOTSUPP;
> + unsigned int pol_bits;
>
> /*
> * If the PWM channel is disabled, make sure to turn on the
> @@ -91,9 +92,12 @@ static int mxs_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
> * only take effect at the beginning of a new period, avoiding
> * glitches.
> */
> +
> + pol_bits = state->polarity == PWM_POLARITY_NORMAL ?
> + PERIOD_POLARITY_NORMAL : PERIOD_POLARITY_INVERSE;
> writel(duty_cycles << 16,
> mxs->base + PWM_ACTIVE0 + pwm->hwpwm * 0x20);
> - writel(PERIOD_PERIOD(period_cycles) | PERIOD_POLARITY_NORMAL | PERIOD_CDIV(div),
> + writel(PERIOD_PERIOD(period_cycles) | pol_bits | PERIOD_CDIV(div),
> mxs->base + PWM_PERIOD0 + pwm->hwpwm * 0x20);

Is the avoidance of glitches still true when period changes? I assume
that yes, but I wonder if you tested that.

Best regards
Uwe

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

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