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

[From: Kalle Valo]

"ext Siarhei Siamashka" <siarhei.siamashka at gmail.com> writes:

> With a simple patch that just retries operation on such error,
> wireless connection got stable. After a long test with the test
> script, no problems were detected. The following lines could be
> occasionally seen in dmesg log and it  proves that there were
> potential connection drops encountered, but they all did not cause any
> troubles in reality (MD5 of downloaded file was always OK):
> [50559.494232] Dynamic PSM
> [50559.494323] PSM timeout 1000 ms
> [50622.038146] We haven't got a READY interrupt from WAKEUP. (firmware
> crashed?)
> [50622.038269] Try again...
> [50622.038330] succeeded!!!

Yeah, sounds like the SPI bus is not reliable because retransmitting
the frame succeeds.

> I'm attaching the same patch here. It is not very clean, but it does
> the job (for Nokia 770).

Thanks. I'm sure this patch helps with SPI problems.

> And I have encountered other problems with WLAN driver that are yet to
> be solved. For example, sometimes speed drops to ~30KB/s (that's still
> an unresolved mystery to me).

Do you see this only with 770 or also with N800/N810?

> 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.

Sorry, I'm not familiar with OMAP 1710 McBSP, so I can't comment.

-- 
Kalle Valo