Hi, On Thu, Aug 25, 2016 at 07:50:11PM +0200, Olliver Schinagl wrote: > From: Olliver Schinagl <[email protected]> > > The pwm-block of some of the sunxi chips feature a 'ready' flag to > indicate the software that it is ready for new commands. > > Right now, when we call pwm_config and set the period, we write the > values to the registers, and turn off the clock to the IP. Because of > this, the hardware does not have time to configure the hardware and set > the 'ready' flag. > > By running the clock just before making new changes and before checking > if the hardware is ready, the hardware has time to reconfigure itself > and set the clear the flag appropriately. > > Signed-off-by: Olliver Schinagl <[email protected]> > --- > drivers/pwm/pwm-sun4i.c | 43 +++++++++++++++++++++++++------------------ > 1 file changed, 25 insertions(+), 18 deletions(-) > > diff --git a/drivers/pwm/pwm-sun4i.c b/drivers/pwm/pwm-sun4i.c > index 5e97c8a..dd198c3 100644 > --- a/drivers/pwm/pwm-sun4i.c > +++ b/drivers/pwm/pwm-sun4i.c > @@ -105,6 +105,22 @@ static int sun4i_pwm_config(struct pwm_chip *chip, > struct pwm_device *pwm, > u64 clk_rate, div = 0; > unsigned int prescaler = 0; > int err; > + int ret = 0; > + > + /* Let the PWM hardware run before making any changes. We do this to > + * allow the hardware to have some time to clear the 'ready' flag. > + */
This is not the proper comment style.
> + err = clk_prepare_enable(sun4i_pwm->clk);
> + if (err) {
> + dev_err(chip->dev, "failed to enable PWM clock\n");
> + return err;
> + }
New line please.
> + spin_lock(&sun4i_pwm->ctrl_lock);
> + val = sun4i_pwm_readl(sun4i_pwm, PWM_CTRL_REG);
> + clk_gate = val & BIT_CH(PWM_CLK_GATING, pwm->hwpwm);
> + val |= BIT_CH(PWM_CLK_GATING, pwm->hwpwm);
What are you doing here? You clear a bit, and then put the same one
back in?
> + sun4i_pwm_writel(sun4i_pwm, val, PWM_CTRL_REG);
> + spin_unlock(&sun4i_pwm->ctrl_lock);
>
> clk_rate = clk_get_rate(sun4i_pwm->clk);
>
> @@ -137,7 +153,9 @@ static int sun4i_pwm_config(struct pwm_chip *chip, struct
> pwm_device *pwm,
>
> if (div - 1 > PWM_PRD_MASK) {
> dev_err(chip->dev, "period exceeds the maximum
> value\n");
> - return -EINVAL;
> + ret = -EINVAL;
> + spin_lock(&sun4i_pwm->ctrl_lock);
Uh? That's really suspicious. And even if right, please don't do that,
this is just really bad for the comprehension of the workflow.
Maxime
--
Maxime Ripard, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com
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