GTA01V3/V4 LCD framebuffer problem

Nils Faerber nils.faerber at
Thu Jul 19 16:59:36 CEST 2007

I am currently trying to get suspend/resume working with the current NEO
GTA01 devices and encountered a strange issue...

With the latest kernel I can successfully suspend and resume
the machine. Most devices seem to be fine after resume, including USB,
audio, touchscreen, modem, etc.
But the LCD just displays a blank white screen with backlight switched
on. And this does not change anymore until reboot.

I looked through the s3c2410fb.c code and found it to be appearingly
good, concerning suspend/resume. So in theory it should work just that
it does not.

I also found by some additional debugging output that the LCD controller
registers are still properly setup but in control register 5 I see that
the status bits for the vertical and horizontal back porch are always set.

Does that mean anything? Is it hanging at the back porch?
Could it be possible that, though the LCD clock is reenabled on resume,
the clock does not actually start to tick (for some reason)?
Another suspicion I have is that probably the LCD_RESET is deasserted
upon resume - I have not checked its state after resume (yet). This
could probably also cause the TFT itself to become deaf.

It's quite strange and also a pity - so close to be mostly usable ;)

So any hint where and what for to look would be greatly appreciated! I
am willing to do the work, I am just new to this platform and need some
hints where to look for such kind of glitches...

Thanks in advance!

  nils faerber

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