Wacky Racers on Glamo

Andy Green andy at openmoko.com
Tue Jul 29 19:58:41 CEST 2008

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Somebody in the thread at some point said:

|> The Glamo docs also say that for 4ms after reset, we cannot touch the
|> registers, and that matches a lot of the race outcomes I see, PLLs not
|> started again sometimes even when we ran the correct code to start them,
|> stuff passing PLL lock tests and then brain damage later when it updates
|> cursor in framebuffer or brings up SD Card again.  The brain damage is
|> very ugly to debug because one race outcome is the Glamo just jams nWAIT
|> down forever if it isn't in a state to service your read [1].
| Is this #''Openmoko Bug #1687: FR LCD goes blank suddenly''?
| Do we need a hw-fix for this eventually?

Believe so.

It only seems to get provoked during some suspend and resume, I have
never seen the White Screen business just in normal use.

I also monitored the GPIO side before the divider and never saw a glitch
from there.  But I can make a reset on Glamo any time just by the scope
probe, and the visible and logical symptoms fit perfectly.

We should be able to work around it in software just by storing and
restoring the important registers.  But today I found it can act
differently with all the normal registers correctly restored, some state
inside Glamo DRAM maybe.

- -Andy
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