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

[Lucas Stach]

Am Mittwoch, den 08.05.2019, 19:18 +0200 schrieb Guido Günther:
> Hi,
> On Thu, Mar 07, 2019 at 11:30:51AM +0100, Guido Günther wrote:
> > This adds initial support for the NWL MIPI DSI Host controller found on i.MX8
> > SoCs.
> > 
> > It adds support for the i.MX8MQ but the same IP core can also be found on e.g.
> > i.MX8QXP. I added the necessary hooks to support other imx8 variants but since
> > I only have imx8mq boards to test I omitted the platform data for other SoCs.
> > 
> > The code is based on NXPs BSP so I added Robert Chiras as Co-authored-by but
> > I'm happy to swap Author: and Co-authored-by: if that looks more appropriate.
> > The most notable changes over the BSP driver are
> >  - Calculate HS mode timing from phy_configure_opts_mipi_dphy
> >  - Perform all clock setup via DT
> >  - Merge nwl-imx and nwl drivers
> >  - Add B0 silion revision quirk
> > 
> > Posting this is likely a bit premature (hence v0) but I wanted for one show how
> > this hooks into the mixel dphy posted earlier [1] and avoid duplicating work.
> > So if there's other code out there doing the same I'm be happy to merge
> > efforts.
> 
> Since this is likely not going anywhere until we have a dcss driver aimed
> for mainline I'm not going spam the list with further revisions. However
> the 5.x version is maintained here:
> 
>     https://source.puri.sm/guido.gunther/linux-imx8/tree/forward-upstream/next-20190506/imx-nwl/v1-wip
> 
> Feedback is still welcome. It'll eventually be forwarded to newer
> linux-next versions.
> 
> Changes over the posted version are:
> 
> - Add quirk for IMQ8MQ silicon B0 revision to not mess with the
>   system reset controller on power down since enable won't work
>   afterwards otherwise.
> - Disable tx esc clock *after* the phy power down to unbreak
>   disable/enable (unblank/blank)
> - Drop devm_free_irq() handled by the device driver core
> - Add ports to dt binding docs
> - Select GENERIC_PHY_MIPI_DPHY instead of GENERIC_PHY for
>   phy_mipi_dphy_get_default_config
> - Include drm_print.h to fix build on next-20190408
> - Drop some debugging messages
> - Newline terminate all DRM_ printouts
> 
> If somebody is working on DCSS support it'd be cool to know since this
> driver is currently a component of imx-display-subsystem which will only
> work out if dcss is handled like this as well.

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.

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.

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.

Regards,
Lucas