Re: [PATCH 00/11] Plane Color Pipeline support for MediaTek

[CK Hu (胡俊光)]

On Fri, 2026-02-06 at 08:28 -0500, Nícolas F. R. A. Prado wrote:
> On Fri, 2026-02-06 at 11:09 +0200, Pekka Paalanen wrote:
> > On Fri, 2 Jan 2026 13:40:21 -0500
> > Harry Wentland <harry.wentland@xxxxxxx> wrote:
> > 
> > > On 2026-01-01 07:37, Shengyu Qu wrote:
> > > > 
> > > > 
> > > > 在 2025/12/30 02:53, Shengyu Qu 写道:  
> > > > > 
> > > > > 
> > > > > 在 2025/12/24 3:44, NÃ colas F. R. A. Prado 写道:  
> > 
> > > > > > Given the lack of support for writeback connectors on the
> > > > > > MediaTek KMS driver, combined with limited hardware
> > > > > > documentation, I haven't been able to verify the correctness
> > > > > > of
> > > > > > each curve, only that they were visually sane (gamma curves
> > > > > > made
> > > > > > the image on the display brighter, while inverse gamma made
> > > > > > it
> > > > > > darker).  
> > > > > 
> > > > > Hmmm I don't think this is acceptable. sRGB/scRGB has two
> > > > > transfer
> > > > > functions mentioned in original specification[1]. To keep color
> > > > > accuracy, we need someone from mediatek confirm whether this is
> > > > > piece- wise or pure power 2.2 transfer function, this is
> > > > > already
> > > > > done in original amdgpu color pipeline series, sRGB means
> > > > > piece-wise while also dedicated power 2.2 function exists.  
> > > 
> > > Not sure what you mean with this not being acceptable. This is
> > > about
> > > enabling HW support for this functionality. Not every HW has
> > > writeback for testing. At some point you'll have to trust the
> > > driver
> > > devs if you're going to use functionality of the driver. We're not
> > > always going to get everything perfect, but if that's really such a
> > > worry you can always use shaders to do precisely what you want.
> > > 
> > 
> > Hi Harry,
> > 
> > yes, but I understood that in this case, the hardware documentation
> > available is so vague that it's impossible to say what it will
> > actually
> > do. There are no formulas given or referenced in the documentation,
> > are
> > there, Nícolas?
> 
> No formulas at all, the only documentation I had available for the
> curves was the register definition, which simply lists the possible
> values: SCRGB, BT709, BT2020, HLG.

Hi, Nicolas:

In [1], it shows OVL could output data to WDMA which could write data into DRAM.
Its control is similar to RDMA. RDMA read data from DRAM and WDMA write data into DRAM.
Do you have interest to implement WDMA?
This is just a suggestion.
I could accept we believe what document say first and wait for someone to verify it.

[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/soc/mediatek/mt8195-mmsys.h?h=v7.0-rc1#n8

Regards,
CK

>