linux-kernel - Re: [PATCH v4] gpu/drm: mediatek: call mtk_dsi_stop() after mtk_drm_crtc_atomic

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Message-ID: <1559210770.12373.0.camel@mtksdaap41>
Date:   Thu, 30 May 2019 18:06:10 +0800
From:   CK Hu <ck.hu@...iatek.com>
To:     Hsin-Yi Wang <hsinyi@...omium.org>
CC:     <linux-arm-kernel@...ts.infradead.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Matthias Brugger <matthias.bgg@...il.com>,
        <dri-devel@...ts.freedesktop.org>,
        <linux-mediatek@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4] gpu/drm: mediatek: call mtk_dsi_stop() after
 mtk_drm_crtc_atomic_disable()

Hi, Hsin-Yi:

On Thu, 2019-05-30 at 17:18 +0800, Hsin-Yi Wang wrote:
> mtk_dsi_stop() should be called after mtk_drm_crtc_atomic_disable(), which needs
> ovl irq for drm_crtc_wait_one_vblank(), since after mtk_dsi_stop() is called,
> ovl irq will be disabled. If drm_crtc_wait_one_vblank() is called after last
> irq, it will timeout with this message: "vblank wait timed out on crtc 0". This
> happens sometimes when turning off the screen.
> 
> In drm_atomic_helper.c#disable_outputs(),
> the calling sequence when turning off the screen is:
> 
> 1. mtk_dsi_encoder_disable()
>      --> mtk_output_dsi_disable()
>        --> mtk_dsi_stop();  // sometimes make vblank timeout in atomic_disable
>        --> mtk_dsi_poweroff();
> 2. mtk_drm_crtc_atomic_disable()
>      --> drm_crtc_wait_one_vblank();
>      ...
>        --> mtk_dsi_ddp_stop()
>          --> mtk_dsi_poweroff();
> 
> mtk_dsi_poweroff() has reference count design, change to make mtk_dsi_stop()
> called in mtk_dsi_poweroff() when refcount is 0.

Reviewed-by: CK Hu <ck.hu@...iatek.com>

> 
> Fixes: 0707632b5bac ("drm/mediatek: update DSI sub driver flow for sending commands to panel")
> Signed-off-by: Hsin-Yi Wang <hsinyi@...omium.org>
> ---
> change log v3->v4:
> * add comment in code.
> ---
>  drivers/gpu/drm/mediatek/mtk_dsi.c | 10 +++++++++-
>  1 file changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/mediatek/mtk_dsi.c b/drivers/gpu/drm/mediatek/mtk_dsi.c
> index b00eb2d2e086..730594a91440 100644
> --- a/drivers/gpu/drm/mediatek/mtk_dsi.c
> +++ b/drivers/gpu/drm/mediatek/mtk_dsi.c
> @@ -630,6 +630,15 @@ 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);
> +
>  	if (!mtk_dsi_switch_to_cmd_mode(dsi, VM_DONE_INT_FLAG, 500)) {
>  		if (dsi->panel) {
>  			if (drm_panel_unprepare(dsi->panel)) {
> @@ -696,7 +705,6 @@ static void mtk_output_dsi_disable(struct mtk_dsi *dsi)
>  		}
>  	}
>  
> -	mtk_dsi_stop(dsi);
>  	mtk_dsi_poweroff(dsi);
>  
>  	dsi->enabled = false;