On Mon, 24 May 2004, David Brownell wrote: > Guennadi Liakhovetski wrote: > > > > So, how can the initialisation of the USB chip affect the rest of the PCI > > also without USB-devices attached and without USB-traffic? Does the OHCI > > driver poll? > > It turns on the periodic schedule processing, which means once > every msec it does PCI DMA even if there are no devices connected.
Hm, that could be the reason. But, upon briefly looking through the code, it looked like the driver sets up the timer with a period of min(30ms, urb->interval), but well may be that I misunderstood what was going on there. > On systems where the PCI is marginal, that regular DMA can make > for a lot of trouble ... even though it's just fetching one word > per OHCI controller. One system kept getting "Unrecoverable Error" > exceptions in OHCI, which usually means DMA transfers failing. > > I fixed that a while back on the 2.6 kernels, where right now > OHCI does a reasonable job of turning everything off until it's > really needed ... even suspending the root hub itself, which > reduces power consumption a bunch. The next step would involve > suspending the controller (vs just its root hub), at least on > systems where remote wakeup works properly. The transceivers > can detect when devices connect, raising a signal which leads > to resuming the controller (then its root hub). Ok, it, probably, wouldn't be fixed for 2.4 any more (actually, looks like a worthy fix, or not?), is it at least possible to increase the period, and, if yes - how (if it is really 1ms)? And would it help significantly?... Thanks Guennadi --- Guennadi Liakhovetski ------------------------------------------------------- This SF.Net email is sponsored by: Oracle 10g Get certified on the hottest thing ever to hit the market... Oracle 10g. Take an Oracle 10g class now, and we'll give you the exam FREE. http://ads.osdn.com/?ad_id=3149&alloc_id=8166&op=click _______________________________________________ [EMAIL PROTECTED] To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
