linux-kernel - Re: [PATCH v12 06/10] drm/mediatek: Add MT8195 External DisplayPort support

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Message-ID: <ed0396cc-c180-1c60-20ec-83b4d4eb1993@collabora.com>
Date:   Mon, 27 Jun 2022 12:17:52 +0200
From:   AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
To:     Bo-Chen Chen <rex-bc.chen@...iatek.com>, chunkuang.hu@...nel.org,
        p.zabel@...gutronix.de, daniel@...ll.ch, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, mripard@...nel.org,
        tzimmermann@...e.de, matthias.bgg@...il.com, deller@....de,
        airlied@...ux.ie
Cc:     msp@...libre.com, granquet@...libre.com, jitao.shi@...iatek.com,
        wenst@...omium.org, ck.hu@...iatek.com,
        dri-devel@...ts.freedesktop.org,
        linux-mediatek@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-fbdev@...r.kernel.org,
        Project_Global_Chrome_Upstream_Group@...iatek.com
Subject: Re: [PATCH v12 06/10] drm/mediatek: Add MT8195 External DisplayPort
 support

Il 27/06/22 10:03, Bo-Chen Chen ha scritto:
> From: Guillaume Ranquet <granquet@...libre.com>
> 
> This patch adds External DisplayPort support to the mt8195 eDP driver.
> 
> Signed-off-by: Guillaume Ranquet <granquet@...libre.com>
> [Bo-Chen: Move some dp features here and modify for reviewers' comments.]
> Signed-off-by: Bo-Chen Chen <rex-bc.chen@...iatek.com>
> ---
>   drivers/gpu/drm/mediatek/mtk_dp.c | 217 ++++++++++++++++++++++++------
>   1 file changed, 174 insertions(+), 43 deletions(-)
> 
> diff --git a/drivers/gpu/drm/mediatek/mtk_dp.c b/drivers/gpu/drm/mediatek/mtk_dp.c
> index 9e9b516409e2..1697c61462b7 100644
> --- a/drivers/gpu/drm/mediatek/mtk_dp.c
> +++ b/drivers/gpu/drm/mediatek/mtk_dp.c
> @@ -111,6 +111,7 @@ struct mtk_dp {
>   	struct regmap *regs;
>   
>   	bool enabled;
> +	bool has_fec;
>   
>   	struct drm_connector *conn;
>   };
> @@ -123,6 +124,11 @@ static struct regmap_config mtk_dp_regmap_config = {
>   	.name = "mtk-dp-registers",
>   };
>   
> +static bool mtk_dp_is_edp(struct mtk_dp *mtk_dp)
> +{
> +	return mtk_dp->next_bridge;
> +}
> +
>   static struct mtk_dp *mtk_dp_from_bridge(struct drm_bridge *b)
>   {
>   	return container_of(b, struct mtk_dp, bridge);
> @@ -401,6 +407,20 @@ static bool mtk_dp_plug_state(struct mtk_dp *mtk_dp)
>   		  HPD_DB_DP_TRANS_P0_MASK);
>   }
>   
> +static bool mtk_dp_plug_state_avoid_pulse(struct mtk_dp *mtk_dp)
> +{
> +	int wait;
> +
> +	for (wait = 7; !mtk_dp_plug_state(mtk_dp) && wait > 0; --wait)
> +		/* Avoid short pulses on the HPD isr */
> +		usleep_range(1000, 5000);
> +
> +	if (wait == 0)
> +		return false;
> +

You can as well use existing APIs for that:

static bool mtk_dp_plug_state_avoid_pulse(struct mtk_dp *mtk_dp)
{
	int ret;

	return !!(readx_poll_timeout(mtk_dp_plug_state, mtk_dp, ret, ret,
				     4000, (7 * 4000)));
}

P.S.: I've used 4000 instead of 5000 on purpose, check the definition of
       readx_poll_timeout for more information.

All the rest of this commit looks good to me.

Cheers,
Angelo