linux-kernel - Re: [PATCH v4 0/5] Support alpha blending in MTK display driver

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Message-ID: <26504ee033e506db17fc130d08b2f85a187af2e7.camel@mediatek.com>
Date: Fri, 13 Sep 2024 02:56:01 +0000
From: Shawn Sung (宋孝謙) <Shawn.Sung@...iatek.com>
To: "alpernebiyasak@...il.com" <alpernebiyasak@...il.com>,
	"linux-mediatek@...ts.infradead.org" <linux-mediatek@...ts.infradead.org>,
	"chunkuang.hu@...nel.org" <chunkuang.hu@...nel.org>
CC: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"wenst@...omium.org" <wenst@...omium.org>, "daniel@...ll.ch"
	<daniel@...ll.ch>, "p.zabel@...gutronix.de" <p.zabel@...gutronix.de>,
	CK Hu (胡俊光) <ck.hu@...iatek.com>,
	"dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
	"shawn.sung@...iatek.corp-partner.google.com"
	<shawn.sung@...iatek.corp-partner.google.com>, "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>, "angelogioacchino.delregno@...labora.com"
	<angelogioacchino.delregno@...labora.com>
Subject: Re: [PATCH v4 0/5] Support alpha blending in MTK display driver

Hi Alper,

On Thu, 2024-09-12 at 23:29 +0300, Alper Nebi Yasak wrote:
> Hi,
> 
> On 2024-07-31 16:34 +03:00, Chun-Kuang Hu wrote:
> > Hi, Shawn:
> > 
> > Hsiao Chien Sung via B4 Relay
> > <devnull+shawn.sung.mediatek.com@...nel.org> 於 2024年7月17日 週三
> > 下午1:24寫道：
> > > 
> > > Support "Pre-multiplied" and "None" blend mode on MediaTek's
> > > chips by
> > > adding correct blend mode property when the planes init.
> > > Before this patch, only the "Coverage" mode (default) is
> > > supported.
> > 
> > For the whole series, applied to mediatek-drm-next [1], thanks.
> > 
> > [1] 
> > https://git.kernel.org/pub/scm/linux/kernel/git/chunkuang.hu/linux.git/log/?h=mediatek-drm-next
> 
> I am seeing broken colors on an MT8173 Chromebook with next-20240912,
> which goes away if I git-revert this series (commits 1f66fe62cc09
> eb17c5909481 a3f7f7ef4bfe 59e9d9de25f0 4225d5d5e779).

Thank you for your feedback. I apologize for the delay in my response;
I was just notified of your email by my colleague.

> 
> To illustrate, I took a picture [1] of some color mixing diagrams
> from
> Wikipedia [2]. Do you have an idea of what goes wrong?

Based on the provided pictures, it appears that this issue is related
to the way the MT8173 chip handles alpha channel (ARGB -> RGBA), which
differes from the behavior of later chips.

> 
> (I'm busy with too many things so I don't want to debug it now...)
> 
> [1] https://i.imgur.com/tNFvovB.jpeg
> [2] https://en.wikipedia.org/wiki/Color_space#Generic

We will either submit a new fix ASAP or revert this series as a first
step.

Best regards,
Shawn