linux-kernel - Re: [PATCH v3,2/4] drm/mediatek: Separate poweron/poweroff from enable/disable and define new funcs

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Date:   Thu, 17 Mar 2022 20:02:21 +0800
From:   Rex-BC Chen <rex-bc.chen@...iatek.com>
To:     <xinlei.lee@...iatek.com>, <chunkuang.hu@...nel.org>,
        <p.zabel@...gutronix.de>, <airlied@...ux.ie>, <daniel@...ll.ch>,
        <matthias.bgg@...il.com>
CC:     <dri-devel@...ts.freedesktop.org>,
        <linux-mediatek@...ts.infradead.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>,
        <Project_Global_Chrome_Upstream_Group@...iatek.com>,
        <jitao.shi@...iatek.com>
Subject: Re: [PATCH v3,2/4] drm/mediatek: Separate poweron/poweroff from
 enable/disable and define new funcs

Hello Xinlei,

On Thu, 2022-03-17 at 15:53 +0800, xinlei.lee@...iatek.com wrote:
> From: Jitao Shi <jitao.shi@...iatek.com>
> 
> In order to match the changes of "Use the drm_panel_bridge API",
> the poweron/poweroff of dsi is extracted from enable/disable and
> defined as new funcs (pre_enable/post_disable).
> 
> Fixes: 2dd8075d2185 ("drm/mediatek: mtk_dsi: Use the drm_panel_bridge
> API")
> 
> Signed-off-by: Jitao Shi <jitao.shi@...iatek.com>
> Signed-off-by: Xinlei Lee <xinlei.lee@...iatek.com>
> ---
>  drivers/gpu/drm/mediatek/mtk_dsi.c | 45 +++++++++++++++++-----------
> --
>  1 file changed, 26 insertions(+), 19 deletions(-)
> 
> diff --git a/drivers/gpu/drm/mediatek/mtk_dsi.c
> b/drivers/gpu/drm/mediatek/mtk_dsi.c
> index 262c027d8c2f..e33caaca11a7 100644
> --- a/drivers/gpu/drm/mediatek/mtk_dsi.c
> +++ b/drivers/gpu/drm/mediatek/mtk_dsi.c
> @@ -679,16 +679,6 @@ 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);
> -
> -	mtk_dsi_switch_to_cmd_mode(dsi, VM_DONE_INT_FLAG, 500);
>  	mtk_dsi_reset_engine(dsi);
>  	mtk_dsi_lane0_ulp_mode_enter(dsi);
>  	mtk_dsi_clk_ulp_mode_enter(dsi);
> @@ -703,17 +693,9 @@ static void mtk_dsi_poweroff(struct mtk_dsi
> *dsi)
>  
>  static void mtk_output_dsi_enable(struct mtk_dsi *dsi)
>  {
> -	int ret;
> -
>  	if (dsi->enabled)
>  		return;
>  
> -	ret = mtk_dsi_poweron(dsi);
> -	if (ret < 0) {
> -		DRM_ERROR("failed to power on dsi\n");
> -		return;
> -	}
> -
>  	mtk_dsi_set_mode(dsi);
>  	mtk_dsi_clk_hs_mode(dsi, 1);
>  
> @@ -727,7 +709,16 @@ static void mtk_output_dsi_disable(struct
> mtk_dsi *dsi)
>  	if (!dsi->enabled)
>  		return;
>  
> -	mtk_dsi_poweroff(dsi);
> +	/*
> +	 * mtk_dsi_stop() and mtk_dsi_start() is asymmetric, since

Why they are asymmetric?

> +	 * 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);
> +
> +	mtk_dsi_switch_to_cmd_mode(dsi, VM_DONE_INT_FLAG, 500);
>  
>  	dsi->enabled = false;
>  }
> @@ -765,10 +756,26 @@ static void mtk_dsi_bridge_enable(struct
> drm_bridge *bridge)
>  	mtk_output_dsi_enable(dsi);
>  }
>  
> +static void mtk_dsi_bridge_pre_enable(struct drm_bridge *bridge)
> +{
> +	struct mtk_dsi *dsi = bridge_to_dsi(bridge);
> +
> +	mtk_dsi_poweron(dsi);

Should you handle the error of mtk_dsi_poweron?
If you failed to mtk_dsi_bridge_pre_enable and do
mtk_dsi_bridge_enable,
what will happend?

> +}
> +
> +static void mtk_dsi_bridge_post_disable(struct drm_bridge *bridge)
> +{
> +	struct mtk_dsi *dsi = bridge_to_dsi(bridge);
> +
> +	mtk_dsi_poweroff(dsi);

If you failed to mtk_dsi_bridge_disable and you do
mtk_dsi_bridge_post_disable,
what will happend?
Do you need to handle this?

BRs,
Rex

> +}
> +
>  static const struct drm_bridge_funcs mtk_dsi_bridge_funcs = {
>  	.attach = mtk_dsi_bridge_attach,
>  	.disable = mtk_dsi_bridge_disable,
>  	.enable = mtk_dsi_bridge_enable,
> +	.pre_enable = mtk_dsi_bridge_pre_enable,
> +	.post_disable = mtk_dsi_bridge_post_disable,
>  	.mode_set = mtk_dsi_bridge_mode_set,
>  };
>