Analysis of OUTPUT high GPIO in suspend / DL_GSM
Andy Green
andy at openmoko.com
Sat Feb 23 12:37:28 CET 2008
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> [ 58.325000] GPJ06: OUTPUT 1 <== DL_GSM... what does it do? ***
DL_GSM controls a couple of tristate drivers via an active-low nOE that
are to do with communication to the GSM side as part of an elaborate
scheme that looks like it can in the fullness of time just be replaced
by DL_GSM and one other IO under a FIQ GPIO UART implementation,
removing R4403, U4401 and doing it all from the CPU side.
R4403 (100K to 0V connected to DL_GSM) means we burn 33uA / 108uW by
having OUTPUT 1 in suspend ... hey it all adds up. However setting it
OUTPUT 0 or allowing it to float so R4403 controls it means this dual
tristate driver (always-on BTW) is enabled to drive unknown levels into
bad places.
- -Andy
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