Re: [PATCH v2 4/7] imx-drm: ipuv3-crtc: Implement mode_fixup

[Philipp Zabel <pza@pengutronix.de>]

Hi Russell,

On Sat, Dec 20, 2014 at 03:52:54PM +0000, Russell King - ARM Linux wrote:
> On Thu, Dec 18, 2014 at 06:00:23PM -0800, Steve Longerbeam wrote:
> > Ask the IPU display interface, via ipu_di_adjust_videomode(), to
> > adjust a video mode to meet any DI restrictions. The function takes
> > a subsystem independent videomode, so the drm_display_mode must be
> > converted to videomode first, and then the adjusted mode converted
> > back to a drm_display_mode.
> 
> What is the reason to use videomode (apart from it being subsystem
> independent)?  Do we forsee implementation of other output subsystems
> for the IPU?

There might be the issue of possible CSI -> IC -> DC -> DI passthrough,
where the DI timing must be synchronized to the CSI input signal.
I haven't really thought about how that should be integrated with the
DRM driver mostly because of the 1024 pixel output width maximum in the
IC, which limits the usefulness somewhat.
I like the use of struct videomode here for the symmetry with patch 6.
But currently, we could make ipu_di_adjust_videomode take a drm_display_mode
just as well.

regards
Philipp