On Tue, 10 Apr 2012 18:36:49 +0200 Daniel Vetter <daniel at ffwll.ch> wrote: > Well, neither do I have a clue about sdvo, but I think I somewhat > self-consistent explanation for what's going on. > > Sdvo seems to have two timings, one is the output timing which will be > sent over whatever is connected on the other side of the sdvo chip (panel, > hdmi screen, tv), the other is the input timing which will be generated by > the gmch pipe. It looks like sdvo is expected to scale between the two. Correct. And the SDVO encoder in the display engine will always run the clock at 100MHz+ and do data stuffing if the pixel rate is lower than that, but we need to set the right clock multiplier in that case (which we do). > To make things slightly more complicated, we have a bunch of special > cases: > - for lvds panel we always use a fixed output timing, namely > intel_sdvo->sdvo_lvds_fixed_mode, hence that special case. > - sdvo has an interface to generate a preferred input timing for a given > output timing. This is the confusing thing that I've tried to clear up > with the follow-on patches. > - a special requirement is that the input pixel clock needs to be between > 100MHz and 200MHz (likely to keep it within the electromechanical design > range of PCIe). Lower pixel clocks are doubled/quadrupled. > > The thing this patch tries to fix is that the pipe needs to be explicit > instructed to double/quadruple the pixels and needs the correspondingly > higher pixel clock, whereas the sdvo adaptor seems to do that itself and > needs the unadjusted pixel clock. Yeah that sounds right based on my reading of an old spec I have. > This patch tries to fix this mess by > - keeping the output mode timing in the unadjusted plain mode, safe for > the lvds case. > - store the input timing in the adjusted_mode with the adjusted pixel > clock. This way we don't need to frob around with the core crtc mode set > code. > - fixup the pixelclock when constructing the sdvo dtd timing struct. This > is why the first part of the patch is an integral part of the series. > - the is_tv special case can be dropped because input_dtd is equivalent to > adjusted_mode after these changes. Follow-up patches clear this up > further (by simply ripping out intel_sdvo->input_dtd because it's not > needed). > > Hopefully this clears things up a bit. Yep, thanks. Hopefully you'll get your SDVO spec access soon... -- Jesse Barnes, Intel Open Source Technology Center -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 836 bytes Desc: not available URL: <http://lists.freedesktop.org/archives/intel-gfx/attachments/20120410/7ba762e3/attachment.pgp>
