Re: [PATCH 00/14] Add initial support for the Rockchip RK3588 HDMI TX Controller

[neil . armstrong]

Hi,

On 03/06/2024 15:03, Heiko Stuebner wrote:
> Am Montag, 3. Juni 2024, 14:14:17 CEST schrieb Andy Yan:
> > Hi Neil:
> >
> > On 6/3/24 16:55, Neil Armstrong wrote:
> > > Hi Christian,
> > >
> > > On 01/06/2024 15:12, Cristian Ciocaltea wrote:
> > > > The RK3588 SoC family integrates a Quad-Pixel (QP) variant of the
> > > > Synopsys DesignWare HDMI TX controller used in the previous SoCs.
> > > >
> > > > It is HDMI 2.1 compliant and supports the following features, among
> > > > others:
> > > .
> > >
> > > ..
> > >
> > > > * SCDC I2C DDC access
> > > > * TMDS Scrambler enabling 2160p@60Hz with RGB/YCbCr4:4:4
> > > > * YCbCr4:2:0 enabling 2160p@60Hz at lower HDMI link speeds
> > > > * Multi-stream audio
> > > > * Enhanced Audio Return Channel (EARC)
> > > -> Those features were already supported by the HDMI 2.0a compliant HW, just
> > > list the _new_ features for HDMI 2.1
> > >
> > > I did a quick review of your patchset and I don't understand why you need
> > > to add a separate dw-hdmi-qp.c since you only need simple variants of the I2C
> > > bus, infoframe and bridge setup.
> > >
> > > Can you elaborate further ? isn't this Quad-Pixel (QP) TX controller version
> > > detectable at runtime ?
> > >
> > > I would prefer to keep a single dw-hdmi driver if possible.
> >
> >
> >
> > The QP HDMI controller is a completely different variant with totally different
> > registers layout, see PATCH 13/14.
> > I think make it a separate driver will be easier for development and maintenance.
>
> I'm with Andy here. Trying to navigate a driver for two IP blocks really
> sounds taxing especially when both are so different.

I agree, I just wanted more details than "variant of the
Synopsys DesignWare HDMI TX controller", if the register mapping is 100%
different, and does not match at all with the old IP, then it's indeed time
to make a brand new driver, but instead of doing a mix up, it's time to extract
the dw-hdmi code that could be common helpers into a dw-hdmi-common module
and use them.

As I see, no "driver" code can be shared, only DRM plumbings, so perhaps those
plumbing code should go into the DRM core ?

In any case, please add more details on the cover letter, including the detailed
HW differrence and the design you chose so support this new IP.

Neil

> Synopsis also created a new dsi controller for the DSI2 standard, with
> a vastly different registers layout.
>
> I guess at some point there is time to say this really is a new IP ;-) .
>
>
> Though while on that thought, I don't fully understand why both a compiled
> under the dw_hdmi kconfig symbol. People going for a minimal kernel might
> want one or the other, but not both for their specific board.
>
>
> Heiko