linux-kernel - Re: [PATCH] drm/mediatek: dsi: Move mtk_dsi_stop() call back to mtk_dsi

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Message-ID: <CAJMQK-hOxxvkjgOxA6KLLUJxxBehHDQvRo-Y_FLMPLEfkoVMzA@mail.gmail.com>
Date:   Mon, 19 Sep 2022 16:40:34 +0800
From:   Hsin-Yi Wang <hsinyi@...omium.org>
To:     Nícolas F. R. A. Prado 
        <nfraprado@...labora.com>
Cc:     Chun-Kuang Hu <chunkuang.hu@...nel.org>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>, kernel@...labora.com,
        Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...ux.ie>,
        Jitao Shi <jitao.shi@...iatek.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Rex-BC Chen <rex-bc.chen@...iatek.com>,
        Xinlei Lee <xinlei.lee@...iatek.com>,
        dri-devel@...ts.freedesktop.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH] drm/mediatek: dsi: Move mtk_dsi_stop() call back to mtk_dsi_poweroff()

On Mon, Sep 19, 2022 at 4:39 PM Nícolas F. R. A. Prado
<nfraprado@...labora.com> wrote:
>
> As the comment right before the mtk_dsi_stop() call advises,
> mtk_dsi_stop() should only be called after
> mtk_drm_crtc_atomic_disable(). That's because that function calls
> drm_crtc_wait_one_vblank(), which requires the vblank irq to be enabled.
>
> Previously mtk_dsi_stop(), being in mtk_dsi_poweroff() and guarded by a
> refcount, would only be called at the end of
> mtk_drm_crtc_atomic_disable(), through the call to mtk_crtc_ddp_hw_fini().
> Commit cde7e2e35c28 ("drm/mediatek: Separate poweron/poweroff from
> enable/disable and define new funcs") moved the mtk_dsi_stop() call to
> mtk_output_dsi_disable(), causing it to be called before
> mtk_drm_crtc_atomic_disable(), and consequently generating vblank
> timeout warnings during suspend.
>
> Move the mtk_dsi_stop() call back to mtk_dsi_poweroff() so that we have
> a working vblank irq during mtk_drm_crtc_atomic_disable() and stop
> getting vblank timeout warnings.
>
> Fixes: cde7e2e35c28 ("drm/mediatek: Separate poweron/poweroff from enable/disable and define new funcs")
> Signed-off-by: Nícolas F. R. A. Prado <nfraprado@...labora.com>
>
Tested-by: Hsin-Yi Wang <hsinyi@...omium.org>

Tested on mt8183 jacuzzi and mt8186 that this patch fixes the vblank warning.

> ---
>
>  drivers/gpu/drm/mediatek/mtk_dsi.c | 21 ++++++++++-----------
>  1 file changed, 10 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/gpu/drm/mediatek/mtk_dsi.c b/drivers/gpu/drm/mediatek/mtk_dsi.c
> index 9cc406e1eee1..f8ad59771551 100644
> --- a/drivers/gpu/drm/mediatek/mtk_dsi.c
> +++ b/drivers/gpu/drm/mediatek/mtk_dsi.c
> @@ -685,6 +685,16 @@ static void mtk_dsi_poweroff(struct mtk_dsi *dsi)
>         if (--dsi->refcount != 0)
>                 return;
>
> +       /*
> +        * mtk_dsi_stop() and mtk_dsi_start() is asymmetric, since
> +        * mtk_dsi_stop() should be called after mtk_drm_crtc_atomic_disable(),
> +        * which needs irq for vblank, and mtk_dsi_stop() will disable irq.
> +        * mtk_dsi_start() needs to be called in mtk_output_dsi_enable(),
> +        * after dsi is fully set.
> +        */
> +       mtk_dsi_stop(dsi);
> +
> +       mtk_dsi_switch_to_cmd_mode(dsi, VM_DONE_INT_FLAG, 500);
>         mtk_dsi_reset_engine(dsi);
>         mtk_dsi_lane0_ulp_mode_enter(dsi);
>         mtk_dsi_clk_ulp_mode_enter(dsi);
> @@ -735,17 +745,6 @@ static void mtk_output_dsi_disable(struct mtk_dsi *dsi)
>         if (!dsi->enabled)
>                 return;
>
> -       /*
> -        * mtk_dsi_stop() and mtk_dsi_start() is asymmetric, since
> -        * mtk_dsi_stop() should be called after mtk_drm_crtc_atomic_disable(),
> -        * which needs irq for vblank, and mtk_dsi_stop() will disable irq.
> -        * mtk_dsi_start() needs to be called in mtk_output_dsi_enable(),
> -        * after dsi is fully set.
> -        */
> -       mtk_dsi_stop(dsi);
> -
> -       mtk_dsi_switch_to_cmd_mode(dsi, VM_DONE_INT_FLAG, 500);
> -
>         dsi->enabled = false;
>  }
>
> --
> 2.37.1
>