linux-kernel - Re: [PATCH v2] pwm: mtk_disp: Fix the disable flow of disp

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Date:   Tue, 30 May 2023 16:28:24 +0800
From:   Fei Shao <fshao@...omium.org>
To:     Matthias Brugger <matthias.bgg@...il.com>
Cc:     Shuijing Li <shuijing.li@...iatek.com>, thierry.reding@...il.com,
        u.kleine-koenig@...gutronix.de,
        angelogioacchino.delregno@...labora.com,
        devicetree@...r.kernel.org, linux-pwm@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org,
        Project_Global_Chrome_Upstream_Group@...iatek.com,
        jitao.shi@...iatek.com
Subject: Re: [PATCH v2] pwm: mtk_disp: Fix the disable flow of disp_pwm

On Mon, May 29, 2023 at 6:43 PM Matthias Brugger <matthias.bgg@...il.com> wrote:
>
>
>
> On 18/05/2023 13:52, Shuijing Li wrote:
> > There is a flow error in the original mtk_disp_pwm_apply() function.
> > If this function is called when the clock is disabled, there will be a
> > chance to operate the disp_pwm register, resulting in disp_pwm exception.
> > Fix this accordingly.
> >
> > Signed-off-by: Shuijing Li <shuijing.li@...iatek.com>
>
> We are missing a fixes tag here.
> Fixes: 888a623db5d0 ("pwm: mtk-disp: Implement atomic API .apply()")
>
>
> with that:
> Reviewed-by: Matthias Brugger <matthias.bgg@...il.com>

Tested-by: Fei Shao <fshao@...omium.org>

>
> > ---
> > Changes in v2:
> > Use
> > if (A && B) {
> >       something();
> > }
> > instead of
> > if (A) {
> >       if (B) {
> >               something();
> >       }
> > }
> > per suggestion from the previous thread:
> > https://lore.kernel.org/lkml/20230515140346.bxeu6xewi6a446nd@pengutronix.de/
> > ---
> >   drivers/pwm/pwm-mtk-disp.c | 13 +++++--------
> >   1 file changed, 5 insertions(+), 8 deletions(-)
> >
> > diff --git a/drivers/pwm/pwm-mtk-disp.c b/drivers/pwm/pwm-mtk-disp.c
> > index 79e321e96f56..2401b6733241 100644
> > --- a/drivers/pwm/pwm-mtk-disp.c
> > +++ b/drivers/pwm/pwm-mtk-disp.c
> > @@ -79,14 +79,11 @@ static int mtk_disp_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
> >       if (state->polarity != PWM_POLARITY_NORMAL)
> >               return -EINVAL;
> >
> > -     if (!state->enabled) {
> > -             mtk_disp_pwm_update_bits(mdp, DISP_PWM_EN, mdp->data->enable_mask,
> > -                                      0x0);
> > -
> > -             if (mdp->enabled) {
> > -                     clk_disable_unprepare(mdp->clk_mm);
> > -                     clk_disable_unprepare(mdp->clk_main);
> > -             }
> > +     if (!state->enabled && mdp->enabled) {
> > +             mtk_disp_pwm_update_bits(mdp, DISP_PWM_EN,
> > +                                      mdp->data->enable_mask, 0x0);
> > +             clk_disable_unprepare(mdp->clk_mm);
> > +             clk_disable_unprepare(mdp->clk_main);
> >
> >               mdp->enabled = false;
> >               return 0;
>