[PATCH] [RFC] pwm: sun4i: Move pwm_calculate out of spin_lock

Clément Péron peron.clem at gmail.com
Mon Jan 13 01:18:58 PST 2020


Hi,

On Mon, 13 Jan 2020 at 01:40, Alexander <alex.mobigo at gmail.com> wrote:
>
> On Thu, Jan 9, 2020 at 8:31 PM Clément Péron <peron.clem at gmail.com> wrote:
> >
> > pwm_calculate calls clk_get_rate while holding a spin_lock.
> >
> > This create an issue as clk_get_rate() may sleep.
> >
> > Move pwm_calculate out of this spin_lock.
> >
> > Fixes: c32c5c50d4fe ("pwm: sun4i: Switch to atomic PWM")
> > Reported-by: Alex Mobigo <alex.mobigo at gmail.com>
> > Suggested-by: Vasily Khoruzhick <anarsoul at gmail.com>
> > Signed-off-by: Clément Péron <peron.clem at gmail.com>
> > ---
> >
> > Hi,
> >
> > this issue has been reported on linux-sunxi Google groups.
> >
> > I don't have a board with PWM to confirm it.
> >
> > Please wait a tested-by.
> >
> > Thanks,
> > Clément
> >
> >  drivers/pwm/pwm-sun4i.c | 7 +++----
> >  1 file changed, 3 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/pwm/pwm-sun4i.c b/drivers/pwm/pwm-sun4i.c
> > index 1afd41ebd3fd..6b230029dc49 100644
> > --- a/drivers/pwm/pwm-sun4i.c
> > +++ b/drivers/pwm/pwm-sun4i.c
> > @@ -248,19 +248,18 @@ static int sun4i_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
> >                 }
> >         }
> >
> > -       spin_lock(&sun4i_pwm->ctrl_lock);
> > -       ctrl = sun4i_pwm_readl(sun4i_pwm, PWM_CTRL_REG);
> > -
> >         ret = sun4i_pwm_calculate(sun4i_pwm, state, &duty, &period, &prescaler,
> >                                   &bypass);
> >         if (ret) {
> >                 dev_err(chip->dev, "period exceeds the maximum value\n");
> > -               spin_unlock(&sun4i_pwm->ctrl_lock);
> >                 if (!cstate.enabled)
> >                         clk_disable_unprepare(sun4i_pwm->clk);
> >                 return ret;
> >         }
> >
> > +       spin_lock(&sun4i_pwm->ctrl_lock);
> > +       ctrl = sun4i_pwm_readl(sun4i_pwm, PWM_CTRL_REG);
> > +
> >         if (sun4i_pwm->data->has_direct_mod_clk_output) {
> >                 if (bypass) {
> >                         ctrl |= BIT_CH(PWM_BYPASS, pwm->hwpwm);
> > --
> > 2.20.1
> >
> """""""""""""""""
> Tested on my board Pine64+, problems occurs before the patch but not after...
>
> Tested-By: Alexander Finger <alex.mobigo at gmail.com>

Thanks, I will send a v2 with your proper name for the Reported-by tag

Regards,
Clement

> """""""""""""""



More information about the linux-arm-kernel mailing list