Hello Rasmus,
On Mon, Sep 23, 2019 at 10:13:45AM +0200, Rasmus Villemoes wrote:
> In preparation for supporting setting the polarity, switch the driver
> to support the ->apply method.
>
> Signed-off-by: Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx>
> ---
> drivers/pwm/pwm-mxs.c | 62 +++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 62 insertions(+)
>
> diff --git a/drivers/pwm/pwm-mxs.c b/drivers/pwm/pwm-mxs.c
> index 04c0f6b95c1a..c70c26a9ff68 100644
> --- a/drivers/pwm/pwm-mxs.c
> +++ b/drivers/pwm/pwm-mxs.c
> @@ -26,6 +26,7 @@
> #define PERIOD_PERIOD_MAX 0x10000
> #define PERIOD_ACTIVE_HIGH (3 << 16)
> #define PERIOD_INACTIVE_LOW (2 << 18)
> +#define PERIOD_POLARITY_NORMAL (PERIOD_ACTIVE_HIGH | PERIOD_INACTIVE_LOW)
> #define PERIOD_CDIV(div) (((div) & 0x7) << 20)
> #define PERIOD_CDIV_MAX 8
>
> @@ -41,6 +42,66 @@ struct mxs_pwm_chip {
>
> #define to_mxs_pwm_chip(_chip) container_of(_chip, struct mxs_pwm_chip, chip)
>
> +static int mxs_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
> + struct pwm_state *state)
> +{
> + struct mxs_pwm_chip *mxs = to_mxs_pwm_chip(chip);
> + int ret, div = 0;
> + unsigned int period_cycles, duty_cycles;
> + unsigned long rate;
> + unsigned long long c;
> +
> + if (state->polarity != PWM_POLARITY_NORMAL)
> + return -ENOTSUPP;
> +
> + rate = clk_get_rate(mxs->clk);
> + while (1) {
> + c = rate / cdiv[div];
> + c = c * state->period;
> + do_div(c, 1000000000);
> + if (c < PERIOD_PERIOD_MAX)
> + break;
> + div++;
> + if (div >= PERIOD_CDIV_MAX)
> + return -EINVAL;
> + }
> +
> + period_cycles = c;
> + c *= state->duty_cycle;
> + do_div(c, state->period);
> + duty_cycles = c;
> +
> + /*
> + * If the PWM channel is disabled, make sure to turn on the clock
> + * before writing the register. Otherwise, keep it enabled.
> + */
> + if (!pwm_is_enabled(pwm)) {
> + ret = clk_prepare_enable(mxs->clk);
> + if (ret)
> + return ret;
> + }
> +
> + writel(duty_cycles << 16,
> + mxs->base + PWM_ACTIVE0 + pwm->hwpwm * 0x20);
> + writel(PERIOD_PERIOD(period_cycles) | PERIOD_POLARITY_NORMAL | PERIOD_CDIV(div),
> + mxs->base + PWM_PERIOD0 + pwm->hwpwm * 0x20);
> +
> + if (state->enabled) {
> + if (!pwm_is_enabled(pwm)) {
> + /*
> + * The clock was enabled above. Just enable
> + * the channel in the control register.
> + */
> + writel(1 << pwm->hwpwm, mxs->base + PWM_CTRL + SET);
> + }
> + } else {
> + if (pwm_is_enabled(pwm))
> + writel(1 << pwm->hwpwm, mxs->base + PWM_CTRL + CLR);
> + clk_disable_unprepare(mxs->clk);
> + }
> + return 0;
> +}
Maybe it would be easier to review when converting from .config +
.enable + .disable to .apply in a single step. (Note this "maybe" is
honest, I'm not entirely sure.)
There is a bug: If the PWM is running at (say) period=100ms, duty=0ms
and we call
pwm_apply_state(pwm, { .enabled = false, duty=100000, period=1000000 });
the output might get high which it should not.
Also there is a bug already in .config: You are not supposed to call
clk_get_rate if the clk might be off.
Best regards
Uwe
--
Pengutronix e.K. | Uwe Kleine-König |
Industrial Linux Solutions | http://www.pengutronix.de/ |
