OLPC wireless startup at boot time

Daniel Drake dsd at laptop.org
Wed Oct 20 05:51:59 EDT 2010

On 20 October 2010 09:14, Hal Murray <hmurray at megapathdsl.net> wrote:
> On lid open, the WiFi LED blinks a few times, finds a few APs, but doesn't
> find my AP.  After a long pause (10+ seconds), it blinks again, finds my AP,
> turns the LED on, and connects to my AP.
> I just measured the pause at 20 seconds.  Is there a reason for that delay?
> Why doesn't the WiFi LED turn on sooner?

The LED-on isn't the point at which it tries to connect. That's the
point at which the association has successfully completed. The LED
doesn't turn on sooner because the connection hasn't been established
until that point.

The question is why does it take so long for the connection to be established?

A 10-12 second reconnect time is to be expected:
 1. A 1 second delay for the device to be probed and initialized on resume
 2. NetworkManager has a 7 second delay hardcoded
 3. A 1-2 second delay for scanning to complete
 4. A 1-2 second delay for authentication, association, key exchange
(if applicable) and DHCP.

We can't really do anything about any of these except #2, which will
go away as soon as we switch to a newer Fedora base version. It's
never gonna be lightning fast.

But, this doesn't explain why you can see a 20 second delay, and
others have reported 30. I've never been able to reproduce this, so I
can't offer a diagnosis. But I once added some diagnostics and
confirmed that the basic things do happen: NM fires off a scan really
quick after the 7 second delay, and the kernel seems to be scanning on
all channels.

Next step is for someone who can reproduce this to confirm my findings
and add further diagnostics.


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