[PATCH v2 2/3] ARM: dts: imx6qdl-wandboard: Add HDMI support

[Russell King - ARM Linux]

On Tue, Oct 15, 2013 at 09:46:18AM +0200, Sascha Hauer wrote:
> On Mon, Oct 14, 2013 at 11:50:29PM +0100, Russell King - ARM Linux wrote:
> > Answers to these two questions may help stop me wasting a lot of time
> > chasing what is a really weird bug.
> > 
> > So, I have X up and running on the Cubox-i carrier-1, using the imx-drm
> > stuff (I've slightly hacked my xf86-armada X driver to get this working.)
> > This works fine - it detects the connectors, selects an appropriate
> > video mode and produces a picture of the correct shape and size.
> > 
> > However... I see really weird effects colouring effects - almost like
> > water over the image.  It's certain colour transitions in the image
> > which seem to trigger this.  There are also certain pixels which
> > "twinkle".
> > 
> > Text looks very strange too.  Rather than the font being crisp and clear,
> > it looks like there's red and green shift to it - but its not that it's
> > all shifted in that way.
> > 
> > Now, if I use the modetest utility from libdrm-2.4.43 to display a SMPTE
> > test pattern, this again looks right, but there are several vertical
> > single pixel lines of noise.  The most striking one is below the upper
> > red bar in the lower dark area.  I have a single pixel noisy vertical
> > line.
> > 
> > I've tried the kernel which Rabeeh supplied, which is based on BSP 4.1.0,
> > and this works fine as far as I can tell with the same image (though,
> > it's a little difficult converting the XWD dump to something that can
> > be directly poked into /dev/fb0..., although this results in R/B swap.)
> > 
> > Any ideas where to start looking?
> 
> This sounds like the wrong clock polarity. Could you try inverting
> sig_cfg.clk_pol in imx-drm/ipuv3-crtc.c?

I tweaked it a different way - I used devmem2 to directly poke at the
register.  Inverting bit 17 (iow, clearing it) seems to fix the
problem.