[Bug 1086] White pixel "noise" corrupts display dynamically after some boots
bugzilla-daemon at bugzilla.openmoko.org
bugzilla-daemon at bugzilla.openmoko.org
Mon Dec 10 08:47:45 CET 2007
http://bugzilla.openmoko.org/cgi-bin/bugzilla/show_bug.cgi?id=1086
------- Additional Comments From andy at openmoko.com 2007-12-10 08:47 -------
Before we got to try the patch I experienced the problem here. I noticed that
when it is corrupting pixels, there is a "hum bar" kind of effect vertically
which somehow alters the colours of pixels in vertical ranks slowly, over a
couple of seconds in a vertical sweep. The pixels are rewritten behind
this "wave front" so the display is still pretty legible.
I also noticed some kind of interlace or interleave is visible making the
pixels "twinkle" where they differ between the two lines.
I wondered immediately if the problem was a slow pixel clock, and the "hum
bar" in that case was the capacitive decay of the TFT gate level over time.
Sure enough when Willie got a 'scope, we measured PCLK in the bad mode and
afterwards in the good mode: ~1.7MHz vs ~24.5MHz or ~15 times slower when it
is bad. So it seems likely this is to do with PLL settings or issue with wait
for lock.
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