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

[Laurentiu Palcu]

Hi Guido,

On Tue, May 28, 2019 at 11:33:00AM +0200, Guido Günther wrote:
> Caution: EXT Email
> 
> 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://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fpatchwork.freedesktop.org%2Fseries%2F58817%2F&data=02%7C01%7Claurentiu.palcu%40nxp.com%7C9924c4628d5f4f98d8a808d6e34f7b26%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%7C636946327839828366&sdata=VZvvhe2WkMVCSOEw5oZDJfy7rsqF7YaEirrkLFC8Icw%3D&reserved=0
>   nwl:  https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fpatchwork.freedesktop.org%2Fseries%2F57686%2F&data=02%7C01%7Claurentiu.palcu%40nxp.com%7C9924c4628d5f4f98d8a808d6e34f7b26%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%7C636946327839838359&sdata=Q4s6OZq1KElktjSXRd2lKBMdg1yPJsWGm8UrSPqqTiE%3D&reserved=0
> 
> 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).

I guess we could do that as well. I'll start adjusting the driver and
take it out of imx-drm, as suggested by Lucas and Daniel. I'll use your
MIPI patches to test with.

thanks,
laurentiu

> 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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