On Wed, Jan 24, 2018 at 08:37:28PM +0100, Giulio Benetti wrote: > > > > Also, how was it tested? This seems quite weird that we haven't caught > > > > that one sooner, and I'm a bit worried about the possible regressions > > > > here. > > > > > > It sounds really strange to me too, > > > because everybody under uboot use "sync:3"(HIGH). > > > I will retry to measure, > > > unfortunately at home I don't have a scope, > > > but I think I'm going to have one soon, because of this. :) > > > > Here I am with scope captures and tcon0 registers dump: > > tcon0_regs => https://pasteboard.co/H4r8Zcs.png > > dclk_d0 => https://pasteboard.co/H4r8QRe.png > > dclk_de => https://pasteboard.co/H4r8zh4R.png > > dclk_vsnc => https://pasteboard.co/H4r8Hye.png > > > > As you can see circled in reg on registers, > > TCON0_IO_POL_REG = 0x00000000. > > But on all the waveforms you can see: > > - dclk_d0: clock phase is 0, but it starts with falling edge, otherwise > > the rising front overlaps dclk rising edge(not good), so to me this is > > falling, then I mean it Negative. > > - dclk_de: de pulse is clearly negative, even if register is 0 and its' > > polarity bit is 0. > > - dclk_vsnc: same as dclk_de > > - dclk_hsync: I didn't take scope screenshot but I can assure you it's > > negative. > > > > You can also check all the other registers about TCON0. > > > > Now I proceed testing it on A33, maybe the peripheral is slightly > > different between Axx SoCs, if I find it that way, > > it should be only a check about SoC or peripheral ID, > > and treat polarity as it should be done. > > Here I am with A33 waveforms: > tcon0_regs => https://pasteboard.co/H4rXfN0M.png > dclk_d0 => https://pasteboard.co/H4rVXwy.png > dclk_de => https://pasteboard.co/H4rWDt8.png > dclk_vsnc => https://pasteboard.co/H4rWRACu.png > dclk_hsync => https://pasteboard.co/H4rWK6I.png > > It behaves the same way as A20, so as I mean IO polarity, > all signals(except D0-D23), are inverted. > For A33 I've used A33-OLinuXino. > For A20 our LiNova1. If you have an A33 handy, you probably want to read that mail: https://lists.freedesktop.org/archives/dri-devel/2017-July/147951.html Especially the 90-phase part. Maxime -- Maxime Ripard, Bootlin (formerly Free Electrons) Embedded Linux and Kernel engineering http://bootlin.com
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