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

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Message-ID: <4143b793-c5b1-4b6d-8547-26a9dc526957@collabora.com>
Date: Tue, 26 Nov 2024 09:57:29 +0100
From: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
To: CK Hu (胡俊光) <ck.hu@...iatek.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>,
 "airlied@...il.com" <airlied@...il.com>,
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 "matthias.bgg@...il.com" <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

Il 26/11/24 08:42, CK Hu (胡俊光) ha scritto:
> 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.
> 
> Both MT8173 HDMI and MT8173 CEC has hot plug detection interrupt.
> I don't know why but MT8173 choose CEC to detect hot plug.
> 
> Does MT8195 CEC has hot plug detection interrupt?
> If it has, may we align the hot plug detection flow with MT8173?
> 

The CEC on MT8195 does have an hotplug detection interrupt, but that *must* be
used exclusively for CEC for one important reason.

While on MT8188 we only have the HDMI (TX) Encoder, MT8195 features both HDMI TX
and HDMI RX and in the specific case of this SoCs, the CEC block is shared between
the two controllers.

If we use the CEC hotplug detection for HDMI-TX, we wouldn't be able to share the
block with the HDMI-RX without hacks.

This is why we need to use the HTPLG/PORD provided by the HDMI-TX block instead of
the CEC one.

> This is not a strong suggestion because I don't know why MT8173 choose CEC to detect.
> I just want more function to be common.

Yeah, I got the point and I would've asked the same question, but for the reasons
that I explained, that's unfortunately not possible :-)

Cheers,
Angelo

> 
> Regards,
> CK
> 
>>
>> Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
>> ---
> 
>>