[Intel-gfx] [RFC PATCH 05/12] drm/i915/dsi: remove unnecessary dsi device callbacks

[Chris Wilson]

On Tue, Jan 27, 2015 at 02:09:21PM +0100, Daniel Vetter wrote:
> On Tue, Jan 27, 2015 at 02:11:18PM +0530, Shobhit Kumar wrote:
> > On 01/23/2015 08:52 PM, Daniel Vetter wrote:
> > >On Fri, Jan 23, 2015 at 03:14:41PM +0530, Shobhit Kumar wrote:
> > >>On 01/22/2015 06:53 PM, Jani Nikula wrote:
> > >>>On Thu, 22 Jan 2015, Shobhit Kumar <shobhit.kumar at linux.intel.com> wrote:
> > >>>>There had been a instance where we had to drive different resolution
> > >>>>(lower) than the native one. Also in VBT there is a field to make this
> > >>>>generic at least from driver perspective to give the needed target
> > >>>>resolution. In case target resolution is same as native, nothing gets
> > >>>>changed, else mode_fixup function adjusts the mode accordingly keeping
> > >>>>timing as same and enabling scalar. Might not be useful in general, but
> > >>>>did find a use internally.
> > >>>
> > >>>Can we just have the driver return the desired mode from .get_modes in
> > >>>that case?
> > >>
> > >>Okay, I think I did not explain correctly. Get modes is modified to give the
> > >>needed target mode only so that userspace creates buffer of the needed
> > >>resolution, but in fixup which is called at modeset, we correct the
> > >>adjusted_mode back to have native resolutions so that modeset is correctly
> > >>done. if we do not do like this, during modeset resolutions will be wrong as
> > >>per the timings.
> > >
> > >I'm confused. Can you please give an example in real numbers about the
> > >different resolution and how it's all fixed up in hw?
> > >
> > >E.g. 800x600 framebuffer -> pfit -> 1024x756 panel,
> > >
> > >get_modes gives 800x600, adjusted mode corrects to 1024x756. And please
> > 
> > We had a 19x12 DSI panel which we needed to drive at 12x8 due to lack of
> > 12x8 panels for testing purposes. So get_modes returned 12x8 so that user
> > space gave 12x8 FBs, and internally in mode_fixup we adjusted correctly for
> > the 19x12 panel timings and enabled pfit
> 
> Hm, is that a real use-case shipping to customers or just a hack for
> development? In the later case I think we can just hardcode the edid for
> edp ...

Also how is this different from userspace creating a 800x600 mode and
giving it to the kernel which then uses the pfitter to display it at
native resolution. That is how it works today. This should also be
possible with a video= parameter...
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre