On Sat, Jan 27, 2018 at 11:07:09PM +0100, Giulio Benetti wrote: > > > > > I don't really know what the polarity of D0 would be just by > > > > > judging at that capture, but we would have noticed if the colors > > > > > were inverted for quite some time now. > > > > > > > > D0-D23 are correct. > > > > > > > > With that capture, I mean to show you instead dclk is inverted, as > > > > dclk samples D0 on falling edge. > > > > > > Ah right, DCLK being the first channel? > > > > Yes, sorry I didn't place a label on channels > > > > > > > > > So 0 is NEGEDGE and 1 is POSEDGE(1/3 of clock phase). > > > > 1/3 clock phase seems enough to me to be considered POSEDGE, > > > > 2/3 instead risks to go too much to the right of D0(even if it > > > > could work). > > > > > > Do you have captures with both settings? > > > > Not now, but asap I'm going to take. > > Here we are: > 1/3 phase: https://pasteboard.co/H4VehON.png > 2/3 phase: https://pasteboard.co/H4Veq8a.png > > Yellow: D0 > Blue: DCLK > > As you can see: > 1/3 phase has DCLK rising edge almost in the middle of D0 > 2/3 phase has DCLK rising edge that comes too late > > I would go for "1/3 phase" for Rising edge and "normal phase" for > Falling edge. > > What do you think? It seems fair. This need a whole lot of comments though :) > > > That it's going to be a nightmare... We've advertised since the very > > > beginning something, and we're about to break it. I'm not sure we want > > > to do that. > > > > I can take care about that. > > But I also think that a lot of displays work because they use only > > DE-mode, almost ignoring HSync and VSync signals(HV-mode). > > > > In any case I have to produce these patches because of my company's > > board based on A20 and A33, and modify defconfig according to it. > > The only technical nightmare I see is to produce a commit for every > > defconfig to be modified and copy-paste che commit-log substituing board > > name(1-2 days of work). > > Problem is testing, but we're speaking about something that probably was > > badly working, but you couldn't see it on display. > > So I think this is only an improvement at the end. > > > > I'm sorry I've taken bad news. > > Drink 1 glass of Spritz to go over! :) > > IMHO I think that we have only to take care about displays that don't have > DE signal. > > If DE signal exists, then displays are driven through DE only for back and > front porch as I know, and on most displays I've used, Hsync and VSync are > ignored. > DE is used not only for Data Enable, but also for sync the very beginning of > frame, the rest of syncing is done by pause between every line sent. > This is should be why nobody noticed it before, > I think almost every display is used in DE mode only. > So, if we fix bug for HSync and VSync, risk should be very low. > Indeed, everybody or almost, use sync:3 because display ignore those 2 > signals (HSync and VSYnc) in favour of DE. > And I don't know how many people checked with oscilloscope signals after > getting display working in a few. I know I did, but I apparently didn't pay attention to that and was more focused on getting the timings right :) But clearly this is a separate discussion that needs to be held on the U-Boot ML. Maxime -- Maxime Ripard, Free Electrons Embedded Linux and Kernel engineering http://free-electrons.com
Attachment:
signature.asc
Description: PGP signature
_______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
