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

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Message-ID: <0711c097f724409941239696f5ab790b302d194a.camel@mediatek.com>
Date: Wed, 27 Nov 2024 03:08:18 +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-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

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.

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>
> > > ---
> > > 
> 
> 
>