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

[Guido Günther]

Hi Laurentiu,
On Tue, May 28, 2019 at 07:03:54AM +0000, Laurentiu Palcu wrote:
> 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.

MIPI support is here:

  mixel:  https://patchwork.freedesktop.org/series/58817/
  nwl:  https://patchwork.freedesktop.org/series/57686/

The NWL driver needs to be adjusted depending on whether we hook into
imx-display-subsystem or not (and then likely moved to the right
subdir). Can we somehow get this moving in sync (even in a non public
tree if necessary).
Cheers,
 -- Guido


> > > 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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