linux-kernel - Re: [PATCH v5 3/6] drm/mediatek: Detect CMDQ execution timeout

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Message-ID: <CAC=S1ng2=XRV9s2t2dxQf1a2V2GsFwhfB8tRxnNDp-QD5eR_xQ@mail.gmail.com>
Date:   Wed, 27 Oct 2021 17:31:49 +0800
From:   Fei Shao <fshao@...omium.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>,
        Jassi Brar <jassisinghbrar@...il.com>,
        Yongqiang Niu <yongqiang.niu@...iatek.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        dri-devel@...ts.freedesktop.org,
        linux-mediatek@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        hsinyi@...omium.org, nancy.lin@...iatek.com,
        singo.chang@...iatek.com
Subject: Re: [PATCH v5 3/6] drm/mediatek: Detect CMDQ execution timeout

Hi Jason,

On Wed, Oct 27, 2021 at 10:19 AM jason-jh.lin <jason-jh.lin@...iatek.com> wrote:
>
> From: Chun-Kuang Hu <chunkuang.hu@...nel.org>
>
> CMDQ is used to update display register in vblank period, so
> it should be execute in next 2 vblank. One vblank interrupt
> before send message (occasionally) and one vblank interrupt
> after cmdq done. If it fail to execute in next 3 vblank,
> tiemout happen.
>
> Signed-off-by: Chun-Kuang Hu <chunkuang.hu@...nel.org>
> Signed-off-by: jason-jh.lin <jason-jh.lin@...iatek.com>
> Reviewed-by: Chun-Kuang Hu <chunkuang.hu@...nel.org>
> ---
>  drivers/gpu/drm/mediatek/mtk_drm_crtc.c | 20 ++++++++++++++++++--
>  1 file changed, 18 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/mediatek/mtk_drm_crtc.c b/drivers/gpu/drm/mediatek/mtk_drm_crtc.c
> index e23e3224ac67..dad1f85ee315 100644
> --- a/drivers/gpu/drm/mediatek/mtk_drm_crtc.c
> +++ b/drivers/gpu/drm/mediatek/mtk_drm_crtc.c
> @@ -54,6 +54,7 @@ struct mtk_drm_crtc {
>  #if IS_REACHABLE(CONFIG_MTK_CMDQ)
>         struct cmdq_client              cmdq_client;
>         u32                             cmdq_event;
> +       u32                             cmdq_vblank_cnt;
>  #endif
>
>         struct device                   *mmsys_dev;
> @@ -227,7 +228,10 @@ struct mtk_ddp_comp *mtk_drm_ddp_comp_for_plane(struct drm_crtc *crtc,
>  static void ddp_cmdq_cb(struct mbox_client *cl, void *mssg)
>  {
>         struct cmdq_cb_data *data = mssg;
> +       struct cmdq_client *cmdq_cl = container_of(cl, struct cmdq_client, client);
> +       struct mtk_drm_crtc *mtk_crtc = container_of(cmdq_cl, struct mtk_drm_crtc, cmdq_client);
>
> +       mtk_crtc->cmdq_vblank_cnt = 0;
>         cmdq_pkt_destroy(data->pkt);
>  }
>  #endif
> @@ -483,6 +487,15 @@ static void mtk_drm_crtc_update_config(struct mtk_drm_crtc *mtk_crtc,
>                                            cmdq_handle->pa_base,
>                                            cmdq_handle->cmd_buf_size,
>                                            DMA_TO_DEVICE);
> +               /*
> +                * CMDQ command should execute in next 3 vblank.
> +                * One vblank interrupt before send message (occasionally)
> +                * and one vblank interrupt after cmdq done,
> +                * so it's timeout after 3 vblank interrupt.
> +                * If it fail to execute in next 3 vblank, timeout happen.
> +                */
> +               mtk_crtc->cmdq_vblank_cnt = 3;
> +
>                 mbox_send_message(mtk_crtc->cmdq_client.chan, cmdq_handle);
>                 mbox_client_txdone(mtk_crtc->cmdq_client.chan, 0);
>         }
> @@ -499,11 +512,14 @@ static void mtk_crtc_ddp_irq(void *data)
>
>  #if IS_REACHABLE(CONFIG_MTK_CMDQ)
>         if (!priv->data->shadow_register && !mtk_crtc->cmdq_client.chan)
> +               mtk_crtc_ddp_config(crtc, NULL);
> +       else if (mtk_crtc->cmdq_vblank_cnt > 0 && --mtk_crtc->cmdq_vblank_cnt == 0)
I think atomic_dec_and_test() does what you want to do here.




> +               DRM_ERROR("mtk_crtc %d CMDQ execute command timeout!\n",
> +                         drm_crtc_index(&mtk_crtc->base));
>  #else
>         if (!priv->data->shadow_register)
> -#endif
>                 mtk_crtc_ddp_config(crtc, NULL);
> -
> +#endif
>         mtk_drm_finish_page_flip(mtk_crtc);
>  }
>
> --
> 2.18.0
>