Messages in this thread | | | Date | Sun, 24 Feb 2002 16:59:37 -0600 | From | Troy Benjegerdes <> | Subject | Re: Flash Back -- kernel 2.1.111 |
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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/
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