[maemo-developers] WLAN Horrible Roaming Performance (N800, OS2008), Software or Hardware Problem ?

[From: Frantisek Dufka]

Siarhei Siamashka wrote:
> I'm sorry. For some unknown reason, I thought that I notified you
> about this problem long ago, but appears that we only discussed this
> issue privately with Frantisek Dufka :(

I think it was discussed also in the "Memory corruption during WLAN use" 
bug too - http://bugs.maemo.org/show_bug.cgi?id=2006


> [50622.038146] We haven't got a READY interrupt from WAKEUP. (firmware
> crashed?)
> [50622.038269] Try again...
> [50622.038330] succeeded!!!
> 
> I'm attaching the same patch here. It is not very clean, but it does
> the job (for Nokia 770).


Not seeing whole code now but I wondered before - isn't it possible just 
to increase timeout  inside 'if (time_after(jiffies, timeout))' instead 
of two passes in loop?


> Also CPU usage is very high because of
> busyloop when waiting till DMA transfer is done. Tasklet, which
> executes the code can't be easily preempted, as far as I understand
> kernel documentation. Maybe it is possible to split tasklet into
> several parts, one of them could be responsible for initiating DMA
> transfer, the other could be activated on DMA transfer completion?
> This all is important for video streaming as any excessive CPU
> resources consumption by WLAN driver negatively impacts video playback
> performance.

I wonder about this too. Sadly I am not so skilled in kernel and don't 
know rules for interrupts, sleeping in kernel, bottom halves etc. so 
splitting the code at least in 770 version (bit banging over McBSP and 
ugly udelay() busylooping for DMA transfer) is too much for my 
abilities. The N800 code looks nicer, where the CPU is burnt there?

Frantisek