Re: [PATCH 1/2 v6] of: add helper to parse display timings

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hi Tomi,

On Monday 08 October 2012 12:01:18 Tomi Valkeinen wrote:
> On Mon, 2012-10-08 at 10:25 +0200, Guennadi Liakhovetski wrote:
> > In general, I might be misunderstanding something, but don't we have to
> > distinguish between 2 types of information about display timings: (1) is
> > defined by the display controller requirements, is known to the display
> > driver and doesn't need to be present in timings DT. We did have some of
> > these parameters in board data previously, because we didn't have proper
> > display controller drivers... (2) is board specific configuration, and is
> > such it has to be present in DT.
> > 
> > In that way, doesn't "interlaced" belong to type (1) and thus doesn't need
> > to be present in DT?
> 
> As I see it, this DT data is about the display (most commonly LCD
> panel), i.e. what video mode(s) the panel supports. If things were done
> my way, the panel's supported timings would be defined in the driver for
> the panel, and DT would be left to describe board specific data, but
> this approach has its benefits.

What about dumb DPI panels ? They will all be supported by a single driver, 
would you have the driver contain information about all known DPI panels ? DT 
seems a good solution to me in this case.

For complex panels where the driver will support a single (or very few) model 
I agree that specifying the timings in DT isn't needed.

> Thus, if you connect an interlaced panel to your board, you need to tell
> the display controller that this panel requires interlace signal. Also,
> pixel clock source doesn't make sense in this context, as this doesn't
> describe the actual used configuration, but only what the panel
> supports.
> 
> Of course, if this is about describing the hardware, the default-mode
> property doesn't really fit in...

Maybe we should rename it to native-mode then ?

-- 
Regards,

Laurent Pinchart