What is the proper way to turn wlan on/off? Other wlan questions.

Werner Almesberger werner at openmoko.org
Thu Dec 18 15:53:49 CET 2008

Andy Green wrote:
> Okie, but the overall semantic would be "put WLAN in lowest power state"
> rather than just cut power to RF side.

rfkill has slightly different goals. To quote from

| Note that disabling the signal output means that the the transmitter
| is to be made to not emit any energy when "blocked".  rfkill is not
| about blocking data transmissions, it is about blocking energy
| emission.

But I think in the end this difference doesn't affect power
consumption. EIO is just generated in the kernel when WLAN is
nominally disabled.

Another question is what else we could do to make WLAN idle power
as low as possible. The answer may very well be "nothing" (besides
driving SDCLK low and tri-stating the rest of the bus). We could
hold the module in reset, but that may actually prevent it from
doing its own even better power saving and we'd get a guaranteed
330uA burn on R7903 (the WLAN_NRESET pull-up) and there may be
another pull-up inside the module. (*)

(*) SDIO_R0D_datasheet_preliminary.pdf (non-public, sorry) says
    that RESET is of type "IH". Naturally, without further

- Werner

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