From: Bjorn Helgaas Date: Thu, 18 Jun 2009 20:46:47 +0000 (-0600) Subject: ACPI: pci_root: check _CRS, then _BBN for downstream bus number X-Git-Tag: v2.6.31-rc1~12^2~9^4~4 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=fbe2b31b4b6dfa790cbc88e00631f3112c4fc54e;p=pandora-kernel.git ACPI: pci_root: check _CRS, then _BBN for downstream bus number To find a host bridge's downstream bus number, we currently look at _BBN first. If _BBN returns a bus number we've already seen, we conclude that _BBN was wrong and look for a bus number in _CRS. However, the spec[1] (figure 5-5 and the example in sec 9.12.1) and an ACPI FAQ[2] suggest that the OS should use _CRS to discover the bus number range, and that _BBN is really intended to bootstrap _CRS methods that reference PCI opregions. This patch makes us always look at _CRS first. If _CRS doesn't supply a bus number, we look at _BBN. If _BBN doesn't exist, we default to zero. This makes the behavior consistent regardless of device discovery order. Previously, if A and B had duplicate _BBNs and we found A first, we'd only look at B's _CRS, whereas if we found B first, we'd only look at A's _CRS. I'm told that Windows discovers host bridge bus numbers using _CRS, so it should be fairly safe to rely on this BIOS functionality. This patch also removes two misleading messages: we printed the "Wrong _BBN value, reboot and use option 'pci=noacpi'" message before looking at _CRS, so we would likely find the bus number in _CRS, the system would work fine, and the user would be confused. The "PCI _CRS %d overrides _BBN 0" message incorrectly assumes _BBN was zero, and it's useless anyway because we print the segment/bus number a few lines later. References: [1] http://www.acpi.info/DOWNLOADS/ACPIspec30b.pdf [2] http://www.acpi.info/acpi_faq.htm _BBN/_CRS discussion http://download.microsoft.com/download/9/8/f/98f3fe47-dfc3-4e74-92a3-088782200fe7/TWAR05005_WinHEC05.ppt (slide 17) http://bugzilla.kernel.org/show_bug.cgi?id=1662 ASUS PR-DLS http://bugzilla.kernel.org/show_bug.cgi?id=1127 ASUS PR-DLSW http://bugzilla.kernel.org/show_bug.cgi?id=1741 ASUS PR-DLS533 Signed-off-by: Bjorn Helgaas Reviewed-by: Alex Chiang CC: Shaohua Li CC: Kenji Kaneshige Signed-off-by: Len Brown --- Reading git-diff-tree failed