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

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Message-ID: <8fec2c21-9d72-4a6b-9f00-01f2e6375831@collabora.com>
Date: Wed, 27 Nov 2024 09:42:20 +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-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
 "linux-mediatek@...ts.infradead.org" <linux-mediatek@...ts.infradead.org>,
 "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
 "simona@...ll.ch" <simona@...ll.ch>,
 "kernel@...labora.com" <kernel@...labora.com>,
 "tzimmermann@...e.de" <tzimmermann@...e.de>,
 "mripard@...nel.org" <mripard@...nel.org>,
 "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>,
 "linux-arm-kernel@...ts.infradead.org"
 <linux-arm-kernel@...ts.infradead.org>,
 "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 27/11/24 04:08, CK Hu (胡俊光) ha scritto:
> On Tue, 2024-11-26 at 09:57 +0100, AngeloGioacchino Del Regno wrote:
>> External email : Please do not click links or open attachments until you have verified the sender or the content.
>>
>>
>> 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.
> 
> OK, please add this information to commit message so that we know why not use CEC to detect hot plug.
> 

Sure, I'll do that for v2.

Cheers,
Angelo

> Regards,
> CK
> 
>>
>>> 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>
>>>> ---
>>>>
>>
>>
>>