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

[Sascha Hauer]

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?

Sascha

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