On Tuesday 26 January 2010 05:48:59 am Rafael J. Wysocki wrote: > On Tuesday 26 January 2010, Jeff Garrett wrote: > > On Sun, Jan 24, 2010 at 11:04:38PM +0100, Rafael J. Wysocki wrote: > > > The following bug entry is on the current list of known regressions > > > from 2.6.32. Please verify if it still should be listed and let me know > > > (either way). > > > > > > Bug-Entry : http://bugzilla.kernel.org/show_bug.cgi?id=15124 > > > Subject : PCI host bridge windows ignored (works with pci=use_crs) > > > Submitter : Jeff Garrett <jeff@xxxxxxxxxxxx> > > > Date : 2010-01-13 5:37 (12 days old) > > > References : http://marc.info/?l=linux-kernel&m=126336296600307&w=4 > > > Handled-By : Yinghai Lu <yinghai@xxxxxxxxxx> > > > Bjorn Helgaas <bjorn.helgaas@xxxxxx> > > > > This regression should still be listed. No patch to test yet. > ... > IIRC, we already know how to fix this ... As far as I know, we do NOT know how to fix this. This regression occurred when we added intel_bus.c because it's not yet smart enough to determine the correct host bridge apertures. Here's what it thinks the bridge aperture is and the Radeon BAR: IOH bus: 00 index 1 mmio: [e0000000, fdffffff] pci 0000:04:00.0: reg 10: [mem 0xd0000000-0xdfffffff 64bit pref] The IOH aperture is obviously not big enough to cover the Radeon BAR. But the host bridge _CRS tells us this: pci_root PNP0A08:00: host bridge window [mem 0xc0000000-0xdfffffff] pci_root PNP0A08:00: host bridge window [mem 0xf0000000-0xfed8ffff] which IS big enough, and we know the bridge is in fact forwarding the [mem 0xd0000000-0xdfffffff 64bit pref] region, because the Radeon works when Jeff boots with "pci=use_crs". I'm quite concerned about this for .33 because I don't think Jeff's configuration (Dell desktop with Intel x58 and large graphics device) is unusual. The benefit of intel_bus.c is on machines with multiple IOHs, where we need to figure out which address ranges go to which IOHs so we can program downstream devices correctly. But even there, _CRS should give us the information we need, so "pci=use_crs" should make these machines work. I think we should remove intel_bus.c before .33. It's breaking boxes and we don't know how to fix it. Even if we do find out how to fix it, I think we should move toward using _CRS instead, because that's what Windows uses and it's an easy way for the firmware to tell us about platform quirks. Bjorn -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
