linux-kernel - Re: [PATCH v4] drm/mediatek: Move mtk_crtc_finish_page_flip() to ddp_cmdq

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Message-ID: <CAAOTY_9SKy0H8Kdhu81_4kxa14RgKhCcnW3FJyKbwraitR5NrA@mail.gmail.com>
Date: Wed, 25 Dec 2024 23:09:29 +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>, 
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>, dri-devel@...ts.freedesktop.org, 
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, 
	linux-mediatek@...ts.infradead.org, fshao@...omium.org, 
	Singo Chang <singo.chang@...iatek.com>, Nancy Lin <nancy.lin@...iatek.com>, 
	Shawn Sung <shawn.sung@...iatek.com>, Project_Global_Chrome_Upstream_Group@...iatek.com
Subject: Re: [PATCH v4] drm/mediatek: Move mtk_crtc_finish_page_flip() to ddp_cmdq_cb()

Hi, Jason:

Jason-JH.Lin <jason-jh.lin@...iatek.com> 於 2024年12月11日 週三 上午11:47寫道：
>
> mtk_crtc_finish_page_flip() is used to notify userspace that a
> page flip has been completed, allowing userspace to free the frame
> buffer of the last frame and commit the next frame.
>
> In MediaTek's hardware design for configuring display hardware by using
> GCE, `DRM_EVENT_FLIP_COMPLETE` should be notified to userspace after
> GCE has finished configuring all display hardware settings for each
> atomic_commit().
>
> Currently, mtk_crtc_finish_page_flip() cannot guarantee that GCE has
> configured all the display hardware settings of the last frame.
> Therefore, to increase the accuracy of the timing for notifying
> `DRM_EVENT_FLIP_COMPLETE` to userspace, mtk_crtc_finish_page_flip()
> should be moved to ddp_cmdq_cb().

Applied to mediatek-drm-fixes [1], thanks.

[1] https://git.kernel.org/pub/scm/linux/kernel/git/chunkuang.hu/linux.git/log/?h=mediatek-drm-fixes

Regards,
Chun-Kuang.

>
> Fixes: 7f82d9c43879 ("drm/mediatek: Clear pending flag when cmdq packet is done")
> Signed-off-by: Jason-JH.Lin <jason-jh.lin@...iatek.com>
> ---
>  drivers/gpu/drm/mediatek/mtk_crtc.c | 25 +++++++++++++++++++------
>  1 file changed, 19 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/gpu/drm/mediatek/mtk_crtc.c b/drivers/gpu/drm/mediatek/mtk_crtc.c
> index eb0e1233ad04..5674f5707cca 100644
> --- a/drivers/gpu/drm/mediatek/mtk_crtc.c
> +++ b/drivers/gpu/drm/mediatek/mtk_crtc.c
> @@ -112,6 +112,11 @@ static void mtk_drm_finish_page_flip(struct mtk_crtc *mtk_crtc)
>
>         drm_crtc_handle_vblank(&mtk_crtc->base);
>
> +#if IS_REACHABLE(CONFIG_MTK_CMDQ)
> +       if (mtk_crtc->cmdq_client.chan)
> +               return;
> +#endif
> +
>         spin_lock_irqsave(&mtk_crtc->config_lock, flags);
>         if (!mtk_crtc->config_updating && mtk_crtc->pending_needs_vblank) {
>                 mtk_crtc_finish_page_flip(mtk_crtc);
> @@ -284,10 +289,8 @@ static void ddp_cmdq_cb(struct mbox_client *cl, void *mssg)
>         state = to_mtk_crtc_state(mtk_crtc->base.state);
>
>         spin_lock_irqsave(&mtk_crtc->config_lock, flags);
> -       if (mtk_crtc->config_updating) {
> -               spin_unlock_irqrestore(&mtk_crtc->config_lock, flags);
> +       if (mtk_crtc->config_updating)
>                 goto ddp_cmdq_cb_out;
> -       }
>
>         state->pending_config = false;
>
> @@ -315,10 +318,15 @@ static void ddp_cmdq_cb(struct mbox_client *cl, void *mssg)
>                 mtk_crtc->pending_async_planes = false;
>         }
>
> -       spin_unlock_irqrestore(&mtk_crtc->config_lock, flags);
> -
>  ddp_cmdq_cb_out:
>
> +       if (mtk_crtc->pending_needs_vblank) {
> +               mtk_crtc_finish_page_flip(mtk_crtc);
> +               mtk_crtc->pending_needs_vblank = false;
> +       }
> +
> +       spin_unlock_irqrestore(&mtk_crtc->config_lock, flags);
> +
>         mtk_crtc->cmdq_vblank_cnt = 0;
>         wake_up(&mtk_crtc->cb_blocking_queue);
>  }
> @@ -606,13 +614,18 @@ static void mtk_crtc_update_config(struct mtk_crtc *mtk_crtc, bool needs_vblank)
>                  */
>                 mtk_crtc->cmdq_vblank_cnt = 3;
>
> +               spin_lock_irqsave(&mtk_crtc->config_lock, flags);
> +               mtk_crtc->config_updating = false;
> +               spin_unlock_irqrestore(&mtk_crtc->config_lock, flags);
> +
>                 mbox_send_message(mtk_crtc->cmdq_client.chan, cmdq_handle);
>                 mbox_client_txdone(mtk_crtc->cmdq_client.chan, 0);
>         }
> -#endif
> +#else
>         spin_lock_irqsave(&mtk_crtc->config_lock, flags);
>         mtk_crtc->config_updating = false;
>         spin_unlock_irqrestore(&mtk_crtc->config_lock, flags);
> +#endif
>
>         mutex_unlock(&mtk_crtc->hw_lock);
>  }
> --
> 2.43.0
>