linux-kernel - Re: [PATCH v1 7/7] drm/mediatek: Introduce HDMI/DDC v2 for MT8195/MT8188

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Message-ID: <559ac08df6614e47c3e8d9d8160b35c9e683c503.camel@mediatek.com>
Date: Mon, 2 Dec 2024 07:27:58 +0000
From: CK Hu (胡俊光) <ck.hu@...iatek.com>
To: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
	"chunkuang.hu@...nel.org" <chunkuang.hu@...nel.org>
CC: "linux-mediatek@...ts.infradead.org" <linux-mediatek@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"tzimmermann@...e.de" <tzimmermann@...e.de>, "simona@...ll.ch"
	<simona@...ll.ch>, "mripard@...nel.org" <mripard@...nel.org>,
	"kernel@...labora.com" <kernel@...labora.com>, "p.zabel@...gutronix.de"
	<p.zabel@...gutronix.de>, "maarten.lankhorst@...ux.intel.com"
	<maarten.lankhorst@...ux.intel.com>, "conor+dt@...nel.org"
	<conor+dt@...nel.org>, "robh@...nel.org" <robh@...nel.org>,
	"dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
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	<matthias.bgg@...il.com>, "krzk+dt@...nel.org" <krzk+dt@...nel.org>
Subject: Re: [PATCH v1 7/7] drm/mediatek: Introduce HDMI/DDC v2 for
 MT8195/MT8188

Hi, Angelo:

On Wed, 2024-11-20 at 13:45 +0100, AngeloGioacchino Del Regno wrote:
> External email : Please do not click links or open attachments until you have verified the sender or the content.
> 
> 
> Add support for the newer HDMI-TX (Encoder) v2 and DDC v2 IPs
> found in MediaTek's MT8195, MT8188 SoC and their variants, and
> including support for display modes up to 4k60 and for HDMI
> Audio, as per the HDMI 2.0 spec.
> 
> HDCP and CEC functionalities are also supported by this hardware,
> but are not included in this commit.
> 
> Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
> ---

[snip]

> +static int mtk_hdmi_v2_enable(struct mtk_hdmi *hdmi)
> +{
> +       int ret;
> +
> +       ret = pm_runtime_resume_and_get(hdmi->dev);

Why turn on power when attach?
Should hot-plug detection be always on so power on when attach?
If so, maybe we need to use CEC to detect hot-plug because CEC has lower power and HDMI power would not be always on.
As you describe previously, CEC just need some hack to support both HDMI Tx and HDMI Rx.
So there is a software solution to use CEC to detect hot-plug in a lower power mode.
And v1 use CEC to detect hot-plug, so it's worth to make v1 and v2 has the same behavior.

Regards,
CK


> +       if (ret) {
> +               dev_err(hdmi->dev, "Cannot resume HDMI\n");
> +               return ret;
> +       }
> +
> +       mtk_hdmi_v2_clk_enable(hdmi);
> +       mtk_hdmi_hw_reset(hdmi);
> +       mtk_hdmi_set_sw_hpd(hdmi, true);
> +
> +       return 0;
> +}
> +

>