[EXT] Re: [PATCH 0/2] drm: imx: Add NWL MIPI DSI host controller support

Laurentiu Palcu laurentiu.palcu at nxp.com
Tue May 28 07:03:54 UTC 2019


Hi Shawn, Lucas,

On Tue, May 28, 2019 at 09:38:02AM +0800, Shawn Guo wrote:
> Caution: EXT Email
> 
> Hi Lucas,
> 
> On Mon, May 27, 2019 at 03:36:53PM +0200, Lucas Stach wrote:
> > We have been looking at how to support DCSS in mainline for a while,
> > but most of the actual work got pushed behind in schedule due to other
> > priorities.
> 
> I have some time to contribute.  Would you suggest how I should help
> here?
> 
> 1. You guys already have something close to completion and do not need
>    more hands.
> 2. You guys already have some preliminary code and can use help from
>    others.
> 3. You guys haven't got anything to start with, but just some design
>    principles that anyone who wants to work on it should consider.
> 
> Which is the one that you want me to read?

We're already working on clearing up the DCSS code and preparing it for
upstreaming. It should be done in the following weeks. The reason we've
been delaying this is because neither HDMI nor MIPI support was present
and, until these are upstream, testing DCSS would be quite impossible.

> 
> > One thing I can can say for certain is that DCSS should not be
> > integrated into imx-drm. It's a totally different hardware and
> > downstream clearly shows that it's not a good idea to cram it into imx-
> > drm.
> 
> I haven't gone deeper into the vendor code, but from a brief looking I
> didn't see so many problems with integrating DCSS into imx-drm.  It's
> not so unreasonable to take imx-drm as an imx-display-subsystem which
> can have multiple CRTCs.  So can you please elaborate a bit on why it's
> really a bad idea?

I'd be interested to hear about this as well.

> 
> > Also the artificial split between hardware control in
> > drivers/gpu/imx/dcss and the DRM driver is just cargo-cult from the
> > IPU/imx-drm split. For the IPU we did it as the IPU has legs in both
> > DRM for the output parts and V4L2 for the input parts. As the DCSS has
> > no video input capabilities the driver could be simplified a lot by
> > moving it all into a single DRM driver.
> 
> Agreed on this.

I also agree on this. DCSS core code will probably be moved inside the
same directory: drivers/gpu/drm/imx/dcss.

Thanks,
laurentiu

> 
> Shawn
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