On Sun, Feb 24, 2002 at 11:51:13PM +0100, Vojtech Pavlik wrote:
> On Sun, Feb 24, 2002 at 02:44:23PM -0800, David S. Miller wrote:
>
> > From: Vojtech Pavlik <vojtech@suse.cz>
> > Date: Sun, 24 Feb 2002 23:39:37 +0100
> >
> > > > happens if you plug in a 66MHz non-capable card to the 50 MHz bus.
> > >
> > > The bus speed drops to 33MHz.
> >
> > Interesting. I'd expect 25 myself ... then we'll definitely need two
> > clock values in struct pci_bus - because the hi-speed one isn't always a
> > double the low one - as shown by your example.
> >
> > You only need one, the current active one.
> >
> > If you think that hot-plug is an issue, the arch dependant could would
> > need to recalculate the "current bus speed" and all would be fine.
> >
> > So why do we need two values?
>
> Oh, you're right. We indeed need only one.
>
> Hmm, now hotplug changing the PCI clock would be quite a lot of fun -
> all running drivers will need to know about the change, because some may
> need to recompute the timings they have programmed into the chips ...
>
> Because virtually disconnecting and reconnecting all the cards for which
> the timings have changed will probably not be an option.
Personally, I think hot-plugging a 33mhz pci device into a 66mhz pci bus
with other active devices on it is either user error or designer error
(should have had a bridge), and a 'virtual disconnect and reconnect' is
reasonable.
You're going to kill (or at least stop) any transactions going on on the
bus while you're physically hot-plugging anway..
-- Troy Benjegerdes | master of mispeeling | 'da hozer' | hozer@drgw.net -----"If this message isn't misspelled, I didn't write it" -- Me ----- "Why do musicians compose symphonies and poets write poems? They do it because life wouldn't have any meaning for them if they didn't. That's why I draw cartoons. It's my life." -- Charles Schulz - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
This archive was generated by hypermail 2b29 : Thu Feb 28 2002 - 21:00:12 EST