Re: [PATCH v5 26/46] pwm: sun4i: implement hardware readout

Alexandre Belloni
2016-03-31T08:00:42Z

On 30/03/2016 at 22:03:49 +0200, Boris Brezillon wrote :
> Implement ->get_state() instead of only initializing the polarity in
> the probe function.
>
> This implementation also takes care of keeping the PWM clk enabled if at
> least one of the PWM exported by the PWM chip is already enabled, which
> should prevent glitches.
>
> Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Reviewed-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>

> ---
> drivers/pwm/pwm-sun4i.c | 74 ++++++++++++++++++++++++++++++++++++-------------
> 1 file changed, 55 insertions(+), 19 deletions(-)
>
> diff --git a/drivers/pwm/pwm-sun4i.c b/drivers/pwm/pwm-sun4i.c
> index 03a99a5..34cb296 100644
> --- a/drivers/pwm/pwm-sun4i.c
> +++ b/drivers/pwm/pwm-sun4i.c
> @@ -252,11 +252,65 @@ static void sun4i_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
> clk_disable_unprepare(sun4i_pwm->clk);
> }
>
> +static void sun4i_pwm_get_state(struct pwm_chip *chip,
> + struct pwm_device *pwm,
> + struct pwm_state *pstate)
> +{
> + struct sun4i_pwm_chip *sun4i_pwm = to_sun4i_pwm_chip(chip);
> + unsigned int clk_rate = clk_get_rate(sun4i_pwm->clk);
> + int prescaler, prescalerid;
> + int ret;
> + u32 val;
> +
> + ret = clk_prepare_enable(sun4i_pwm->clk);
> + if (ret) {
> + dev_err(chip->dev, "Failed to enable PWM clock");
> + return;
> + }
> +
> + val = sun4i_pwm_readl(sun4i_pwm, PWM_CTRL_REG);
> + if (val & BIT_CH(PWM_ACT_STATE, pwm->hwpwm))
> + pstate->polarity = PWM_POLARITY_INVERSED;
> + else
> + pstate->polarity = PWM_POLARITY_NORMAL;
> +
> + if ((val & BIT_CH(PWM_EN, pwm->hwpwm)) &&
> + (val & BIT_CH(PWM_CLK_GATING, pwm->hwpwm)))
> + pstate->enabled = true;
> + else
> + pstate->enabled = false;
> +
> + pstate->period = 0;
> + pstate->duty_cycle = 0;
> + prescalerid = (val >> (PWMCH_OFFSET * pwm->hwpwm)) & PWM_PRESCAL_MASK;
> + prescaler = prescaler_table[prescalerid];
> + if (prescaler) {
> + u64 timens;
> +
> + clk_rate /= prescaler;
> +
> + val = sun4i_pwm_readl(sun4i_pwm, PWM_CH_PRD(pwm->hwpwm));
> +
> + timens = ((val >> 16) & PWM_PRD_MASK) + 1;
> + timens *= NSEC_PER_SEC;
> + do_div(timens, clk_rate);
> + pstate->period = timens;
> +
> + timens = val & PWM_DTY_MASK;
> + timens *= NSEC_PER_SEC;
> + do_div(timens, clk_rate);
> + pstate->duty_cycle = timens;
> + }
> +
> + clk_disable_unprepare(sun4i_pwm->clk);
> +}
> +
> static const struct pwm_ops sun4i_pwm_ops = {
> .config = sun4i_pwm_config,
> .set_polarity = sun4i_pwm_set_polarity,
> .enable = sun4i_pwm_enable,
> .disable = sun4i_pwm_disable,
> + .get_state = sun4i_pwm_get_state,
> .owner = THIS_MODULE,
> };
>
> @@ -307,8 +361,7 @@ static int sun4i_pwm_probe(struct platform_device *pdev)
> {
> struct sun4i_pwm_chip *pwm;
> struct resource *res;
> - u32 val;
> - int i, ret;
> + int ret;
> const struct of_device_id *match;
>
> match = of_match_device(sun4i_pwm_dt_ids, &pdev->dev);
> @@ -345,24 +398,7 @@ static int sun4i_pwm_probe(struct platform_device *pdev)
>
> platform_set_drvdata(pdev, pwm);
>
> - ret = clk_prepare_enable(pwm->clk);
> - if (ret) {
> - dev_err(&pdev->dev, "failed to enable PWM clock\n");
> - goto clk_error;
> - }
> -
> - val = sun4i_pwm_readl(pwm, PWM_CTRL_REG);
> - for (i = 0; i < pwm->chip.npwm; i++)
> - if (!(val & BIT_CH(PWM_ACT_STATE, i)))
> - pwm_set_polarity(&pwm->chip.pwms[i],
> - PWM_POLARITY_INVERSED);
> - clk_disable_unprepare(pwm->clk);
> -
> return 0;
> -
> -clk_error:
> - pwmchip_remove(&pwm->chip);
> - return ret;
> }
>
> static int sun4i_pwm_remove(struct platform_device *pdev)
> --
> 2.5.0
>

--
Alexandre Belloni, Free Electrons
Embedded Linux, Kernel and Android engineering