Re: [PATCH 05/14] pwm: rockchip: Avoid glitches on already running PWMs

Boris Brezillon
2016-06-04T06:26:08Z

On Fri, 3 Jun 2016 13:28:59 -0700
Brian Norris <briannorris@chromium.org> wrote:

> Hi,
>
> Just noticed a few things:
>
> On Fri, Jun 03, 2016 at 10:23:03AM +0200, Boris Brezillon wrote:
> > The current logic will disable the PWM clk even if the PWM was left
> > enabled by the bootloader (because it's controlling a critical device
> > like a regulator for example).
> > Keep the PWM clk enabled if the PWM is enabled to avoid any glitches.
> >
> > Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
> > ---
> > drivers/pwm/pwm-rockchip.c | 24 +++++++++++++++++++++++-
> > 1 file changed, 23 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/pwm/pwm-rockchip.c b/drivers/pwm/pwm-rockchip.c
> > index dfacf7d..798a787 100644
> > --- a/drivers/pwm/pwm-rockchip.c
> > +++ b/drivers/pwm/pwm-rockchip.c
> > @@ -299,6 +299,7 @@ static int rockchip_pwm_probe(struct platform_device *pdev)
> > {
> > const struct of_device_id *id;
> > struct rockchip_pwm_chip *pc;
> > + struct pwm_state state;
> > struct resource *r;
> > int ret;
> >
> > @@ -319,7 +320,7 @@ static int rockchip_pwm_probe(struct platform_device *pdev)
> > if (IS_ERR(pc->clk))
> > return PTR_ERR(pc->clk);
> >
> > - ret = clk_prepare(pc->clk);
> > + ret = clk_prepare_enable(pc->clk);
> > if (ret)
> > return ret;
> >
> > @@ -342,12 +343,33 @@ static int rockchip_pwm_probe(struct platform_device *pdev)
> > dev_err(&pdev->dev, "pwmchip_add() failed: %d\n", ret);
> > }
> >
> > + /* Keep the PWM clk enabled if the PWM appears to be up and running. */
> > + pwm_get_state(pc->chip.pwms, &state);
> > + if (!state.enabled)
>
> Why not just if (!pwm_is_enabled())?

It's a leftover from a previous version where I was deprecating
pwm_enable(). I'll switch back to pwm_enable().

Thanks,

Boris

--
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering