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Message-ID: <CAAOTY_-XUtAGz26KUiXyceY=2OiqEoGMerLt3BpUOKcD36xH+g@mail.gmail.com>
Date: Thu, 22 Aug 2024 22:16:22 +0800
From: Chun-Kuang Hu <chunkuang.hu@...nel.org>
To: jason-jh.lin@...iatek.com
Cc: Chun-Kuang Hu <chunkuang.hu@...nel.org>,
AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
Philipp Zabel <p.zabel@...gutronix.de>, David Airlie <airlied@...il.com>,
Daniel Vetter <daniel@...ll.ch>, Singo Chang <singo.chang@...iatek.com>,
Nancy Lin <nancy.lin@...iatek.com>, Project_Global_Chrome_Upstream_Group@...iatek.com,
dri-devel@...ts.freedesktop.org, linux-mediatek@...ts.infradead.org,
linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2] drm/mediatek: Fix missing configuration flags in mtk_crtc_ddp_config()
Hi, Jason:
Jason-JH.Lin via B4 Relay
<devnull+jason-jh.lin.mediatek.com@...nel.org> 於 2024年8月19日 週一
下午11:26寫道:
>
> From: "Jason-JH.Lin" <jason-jh.lin@...iatek.com>
>
> In mtk_crtc_ddp_config(), mtk_crtc will use some configuration flags to
> generate instructions to cmdq_handle, such as:
> state->pending_config
> mtk_crtc->pending_planes
> plane_state->pending.config
> mtk_crtc->pending_async_planes
> plane_state->pending.async_config
>
> These configuration flags may be set to false when a GCE IRQ comes calling
> ddp_cmdq_cb(). This may result in missing prepare instructions,
> especially if mtk_crtc_update_config() with the flase need_vblank (no need
> to wait for vblank) cases.
>
> Therefore, the mtk_crtc->config_updating flag is set at the beginning of
> mtk_crtc_update_config() to ensure that these configuration flags won't be
> changed when the mtk_crtc_ddp_config() is preparing instructions.
> But somehow the ddp_cmdq_cb() didn't use the mtk_crtc->config_updating
> flag to prevent those pending config flags from being cleared.
>
> To avoid missing the configuration when generating the config instruction,
> the config_updating flag should be added into ddp_cmdq_cb() and be
> protected with spin_lock.
Applied to mediatek-drm-next [1], thanks.
[1] https://git.kernel.org/pub/scm/linux/kernel/git/chunkuang.hu/linux.git/log/?h=mediatek-drm-next
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>
> ---
> Change in v2:
> Add spin_lock protection for config_updating flag.
> ---
> drivers/gpu/drm/mediatek/mtk_crtc.c | 24 ++++++++++++++++++++++++
> 1 file changed, 24 insertions(+)
>
> diff --git a/drivers/gpu/drm/mediatek/mtk_crtc.c b/drivers/gpu/drm/mediatek/mtk_crtc.c
> index 6f34f573e127..b752c0b46383 100644
> --- a/drivers/gpu/drm/mediatek/mtk_crtc.c
> +++ b/drivers/gpu/drm/mediatek/mtk_crtc.c
> @@ -69,6 +69,8 @@ struct mtk_crtc {
> /* lock for display hardware access */
> struct mutex hw_lock;
> bool config_updating;
> + /* lock for config_updating to cmd buffer */
> + spinlock_t config_lock;
> };
>
> struct mtk_crtc_state {
> @@ -107,10 +109,13 @@ static void mtk_crtc_finish_page_flip(struct mtk_crtc *mtk_crtc)
> static void mtk_drm_finish_page_flip(struct mtk_crtc *mtk_crtc)
> {
> drm_crtc_handle_vblank(&mtk_crtc->base);
> +
> + spin_lock(&mtk_crtc->config_lock);
> if (!mtk_crtc->config_updating && mtk_crtc->pending_needs_vblank) {
> mtk_crtc_finish_page_flip(mtk_crtc);
> mtk_crtc->pending_needs_vblank = false;
> }
> + spin_unlock(&mtk_crtc->config_lock);
> }
>
> #if IS_REACHABLE(CONFIG_MTK_CMDQ)
> @@ -314,6 +319,13 @@ static void ddp_cmdq_cb(struct mbox_client *cl, void *mssg)
>
> state = to_mtk_crtc_state(mtk_crtc->base.state);
>
> + spin_lock(&mtk_crtc->config_lock);
> +
> + if (mtk_crtc->config_updating) {
> + spin_unlock(&mtk_crtc->config_lock);
> + goto ddp_cmdq_cb_out;
> + }
> +
> state->pending_config = false;
>
> if (mtk_crtc->pending_planes) {
> @@ -340,6 +352,10 @@ static void ddp_cmdq_cb(struct mbox_client *cl, void *mssg)
> mtk_crtc->pending_async_planes = false;
> }
>
> + spin_unlock(&mtk_crtc->config_lock);
> +
> +ddp_cmdq_cb_out:
> +
> mtk_crtc->cmdq_vblank_cnt = 0;
> wake_up(&mtk_crtc->cb_blocking_queue);
> }
> @@ -571,7 +587,11 @@ static void mtk_crtc_update_config(struct mtk_crtc *mtk_crtc, bool needs_vblank)
> int i;
>
> mutex_lock(&mtk_crtc->hw_lock);
> +
> + spin_lock(&mtk_crtc->config_lock);
> mtk_crtc->config_updating = true;
> + spin_unlock(&mtk_crtc->config_lock);
> +
> if (needs_vblank)
> mtk_crtc->pending_needs_vblank = true;
>
> @@ -625,7 +645,10 @@ static void mtk_crtc_update_config(struct mtk_crtc *mtk_crtc, bool needs_vblank)
> mbox_client_txdone(mtk_crtc->cmdq_client.chan, 0);
> }
> #endif
> + spin_lock(&mtk_crtc->config_lock);
> mtk_crtc->config_updating = false;
> + spin_unlock(&mtk_crtc->config_lock);
> +
> mutex_unlock(&mtk_crtc->hw_lock);
> }
>
> @@ -1068,6 +1091,7 @@ int mtk_crtc_create(struct drm_device *drm_dev, const unsigned int *path,
> drm_mode_crtc_set_gamma_size(&mtk_crtc->base, gamma_lut_size);
> drm_crtc_enable_color_mgmt(&mtk_crtc->base, 0, has_ctm, gamma_lut_size);
> mutex_init(&mtk_crtc->hw_lock);
> + spin_lock_init(&mtk_crtc->config_lock);
>
> #if IS_REACHABLE(CONFIG_MTK_CMDQ)
> i = priv->mbox_index++;
>
> ---
> base-commit: 469f1bad3c1c6e268059f78c0eec7e9552b3894c
> change-id: 20240819-drm-fixup-0819-f51e2d37fcd7
>
> Best regards,
> --
> Jason-JH.Lin <jason-jh.lin@...iatek.com>
>
>
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