[PATCH v7 01/18] soc: mediatek: Disable 9-bit alpha in ETHDR

[Shawn Sung (宋孝謙)]

Hi CK,

On Tue, 2024-05-07 at 05:58 +0000, CK Hu (胡俊光) wrote:
> Hi, Shawn:
> 
> On Thu, 2024-05-02 at 18:38 +0800, Shawn Sung wrote:
> > From: Hsiao Chien Sung <shawn.sung at mediatek.com>
> > 
> > ETHDR 9-bit alpha should be disabled by default,
> > otherwise alpha blending will not work.
> 
> Please explain what is 9-bit alpha. Is ARGB8888 8-bit alpha? I don't
> know there are 9-bit alpha. I would like to know which function would
> be disabled when you disable 9-bit alpha.
> 

When 9-bit alpha is enabled, the original alpha range 0-255 will be
remapped to 0-256 (255 = N/A) for some special case calculation.
Checked with the designer, this setting should be always disabled and
there will be no side effects.

Thanks,
Shawn