Hi, On Fri, Dec 07, 2012 at 03:12:48PM +0100, Philipp Zabel wrote: > Hi, > > Am Montag, den 26.11.2012, 18:56 +0200 schrieb Tomi Valkeinen: > > On 2012-11-26 18:10, Steffen Trumtrar wrote: > > > Hi, > > > > > > On Mon, Nov 26, 2012 at 04:38:36PM +0200, Tomi Valkeinen wrote: > > > > >>> +optional properties: > > >>> + - hsync-active: hsync pulse is active low/high/ignored > > >>> + - vsync-active: vsync pulse is active low/high/ignored > > >>> + - de-active: data-enable pulse is active low/high/ignored > > >>> + - pixelclk-inverted: pixelclock is inverted (active on falling edge)/ > > >>> + non-inverted (active on rising edge)/ > > >>> + ignored (ignore property) > > >> > > >> I think hsync-active and vsync-active are clear, and commonly used, and > > >> they are used for both drm and fb mode conversions in later patches. > > >> > > >> de-active is not used in drm and fb mode conversions, but I think it's > > >> also clear. > > >> > > >> pixelclk-inverted is not used in the mode conversions. It's also a bit > > >> unclear to me. What does it mean that pix clock is "active on rising > > >> edge"? The pixel data is driven on rising edge? How about the sync > > >> signals and DE, when are they driven? Does your HW have any settings > > >> related to those? > > >> > > > > > > Those are properties commonly found in display specs. That is why they > > > are here. > > > If the GPU does not support the property it can be omitted. > > > > So what does the pixelclk-inverted mean? Normally the SoC drives pixel > > data on rising edge, and the panel samples it at falling edge? And > > vice-versa for inverted? Or the other way around? > > > > When is hsync/vsync set? On rising or falling edge of pclk? > > > > My point here is that the pixelclk-inverted is not crystal clear thing, > > like the hsync/vsync/de-active values are. > > > > And while thinking about this, I realized that the meaning of > > pixelclk-inverted depends on what component is it applied to. Presuming > > normal pixclk means "pixel data on rising edge", the meaning of that > > depends on do we consider the SoC or the panel. The panel needs to > > sample the data on the other edge from the one the SoC uses to drive the > > data. > > > > Does the videomode describe the panel, or does it describe the settings > > programmed to the SoC? > > How about calling this property pixelclk-active, active high meaning > driving pixel data on rising edges and sampling on falling edges (the > pixel clock is high between driving and sampling the data), and active > low meaning driving on falling edges and sampling on rising edges? > It is the same from the SoC perspective and from the panel perspective, > and it mirrors the usage of the other *-active properties. >
I think, this would not be a bad idea. I would include Philipps description in the display-timing.txt, as it makes the meaning pretty clear; at least to me. What do the others think about this? Regards, Steffen -- Pengutronix e.K. | | Industrial Linux Solutions | http://www.pengutronix.de/ | Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 | _______________________________________________ dri-devel mailing list dri-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/dri-devel
