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

["Shawn Sung (宋孝謙)" <Shawn.Sung@mediatek.com>]

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@kernel.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