linux-kernel - Re: [PATCH v4 1/2] drm/mediatek: add wait_for

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Date:   Fri, 3 Dec 2021 07:21:30 +0800
From:   Chun-Kuang Hu <chunkuang.hu@...nel.org>
To:     "jason-jh.lin" <jason-jh.lin@...iatek.com>
Cc:     Chun-Kuang Hu <chunkuang.hu@...nel.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Matthias Brugger <matthias.bgg@...il.com>, tzungbi@...gle.com,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        DRI Development <dri-devel@...ts.freedesktop.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-mediatek@...ts.infradead.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Hsin-Yi Wang <hsinyi@...omium.org>,
        Fei Shao <fshao@...omium.org>,
        Nancy Lin <nancy.lin@...iatek.com>, singo.chang@...iatek.com
Subject: Re: [PATCH v4 1/2] drm/mediatek: add wait_for_event for crtc disable
 by cmdq

Hi, Jason:

jason-jh.lin <jason-jh.lin@...iatek.com> 於 2021年12月2日 週四 下午2:41寫道：
>
> mtk_drm_crtc_atomic_disable will send an async cmd to cmdq driver,
> so it may not finish when cmdq_suspend is called sometimes.
>
> Add wait_for_event after sending async disable plane cmd to make
> sure the lastest cmd is done before cmdq_suspend.

Reviewed-by: Chun-Kuang Hu <chunkuang.hu@...nel.org>

>
> Signed-off-by: jason-jh.lin <jason-jh.lin@...iatek.com>
> ---
>  drivers/gpu/drm/mediatek/mtk_drm_crtc.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
>
> diff --git a/drivers/gpu/drm/mediatek/mtk_drm_crtc.c b/drivers/gpu/drm/mediatek/mtk_drm_crtc.c
> index 62529a954b62..0b4012335e7a 100644
> --- a/drivers/gpu/drm/mediatek/mtk_drm_crtc.c
> +++ b/drivers/gpu/drm/mediatek/mtk_drm_crtc.c
> @@ -56,6 +56,7 @@ struct mtk_drm_crtc {
>         struct cmdq_pkt                 cmdq_handle;
>         u32                             cmdq_event;
>         u32                             cmdq_vblank_cnt;
> +       wait_queue_head_t               cb_blocking_queue;
>  #endif
>
>         struct device                   *mmsys_dev;
> @@ -314,6 +315,7 @@ static void ddp_cmdq_cb(struct mbox_client *cl, void *mssg)
>         }
>
>         mtk_crtc->cmdq_vblank_cnt = 0;
> +       wake_up(&mtk_crtc->cb_blocking_queue);
>  }
>  #endif
>
> @@ -700,6 +702,13 @@ static void mtk_drm_crtc_atomic_disable(struct drm_crtc *crtc,
>         mtk_crtc->pending_planes = true;
>
>         mtk_drm_crtc_update_config(mtk_crtc, false);
> +#if IS_REACHABLE(CONFIG_MTK_CMDQ)
> +       /* Wait for planes to be disabled by cmdq */
> +       if (mtk_crtc->cmdq_client.chan)
> +               wait_event_timeout(mtk_crtc->cb_blocking_queue,
> +                                  mtk_crtc->cmdq_vblank_cnt == 0,
> +                                  msecs_to_jiffies(500));
> +#endif
>         /* Wait for planes to be disabled */
>         drm_crtc_wait_one_vblank(crtc);
>
> @@ -980,6 +989,9 @@ int mtk_drm_crtc_create(struct drm_device *drm_dev,
>                                 mtk_crtc->cmdq_client.chan = NULL;
>                         }
>                 }
> +
> +               /* for sending blocking cmd in crtc disable */
> +               init_waitqueue_head(&mtk_crtc->cb_blocking_queue);
>         }
>  #endif
>         return 0;
> --
> 2.18.0
>