Re: [PATCH v2] PCI: Coalesce contiguous regions for host bridges

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On 7/11/21 8:50 PM, Kai-Heng Feng wrote:
Hi Guenter,

On Sat, Jul 10, 2021 at 7:15 AM Guenter Roeck <linux@xxxxxxxxxxxx> wrote:

Hi,

On Thu, Apr 01, 2021 at 09:12:52PM +0800, Kai-Heng Feng wrote:
Built-in graphics on HP EliteDesk 805 G6 doesn't work because graphics
can't get the BAR it needs:
[    0.611504] pci_bus 0000:00: root bus resource [mem 0x10020200000-0x100303fffff window]
[    0.611505] pci_bus 0000:00: root bus resource [mem 0x10030400000-0x100401fffff window]
...
[    0.638083] pci 0000:00:08.1:   bridge window [mem 0xd2000000-0xd23fffff]
[    0.638086] pci 0000:00:08.1:   bridge window [mem 0x10030000000-0x100401fffff 64bit pref]
[    0.962086] pci 0000:00:08.1: can't claim BAR 15 [mem 0x10030000000-0x100401fffff 64bit pref]: no compatible bridge window
[    0.962086] pci 0000:00:08.1: [mem 0x10030000000-0x100401fffff 64bit pref] clipped to [mem 0x10030000000-0x100303fffff 64bit pref]
[    0.962086] pci 0000:00:08.1:   bridge window [mem 0x10030000000-0x100303fffff 64bit pref]
[    0.962086] pci 0000:07:00.0: can't claim BAR 0 [mem 0x10030000000-0x1003fffffff 64bit pref]: no compatible bridge window
[    0.962086] pci 0000:07:00.0: can't claim BAR 2 [mem 0x10040000000-0x100401fffff 64bit pref]: no compatible bridge window

However, the root bus has two contiguous regions that can contain the
child resource requested.

Bjorn Helgaas pointed out that we can simply coalesce contiguous regions
for host bridges, since host bridge don't have _SRS. So do that
accordingly to make child resource can be contained. This change makes
the graphics works on the system in question.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=212013
Suggested-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
Signed-off-by: Kai-Heng Feng <kai.heng.feng@xxxxxxxxxxxxx>

With this patch in place, I can no longer boot the ppc:sam460ex
qemu emulation from nvme. I see the following boot error:

nvme nvme0: Device not ready; aborting initialisation, CSTS=0x0
nvme nvme0: Removing after probe failure status: -19

A key difference seems to be swapped region addresses:

ok:

PCI host bridge to bus 0002:00^M
pci_bus 0002:00: root bus resource [io  0x0000-0xffff]
pci_bus 0002:00: root bus resource [mem 0xd80000000-0xdffffffff] (bus address [0x80000000-0xffffffff])
pci_bus 0002:00: root bus resource [mem 0xc0ee00000-0xc0eefffff] (bus address [0x00000000-0x000fffff])

bad:

PCI host bridge to bus 0002:00^M
pci_bus 0002:00: root bus resource [io  0x0000-0xffff]
pci_bus 0002:00: root bus resource [mem 0xc0ee00000-0xc0eefffff] (bus address [0x00000000-0x000fffff])
pci_bus 0002:00: root bus resource [mem 0xd80000000-0xdffffffff] (bus address [0x80000000-0xffffffff])

and then bar address assignments are swapped/changed.

ok:

pci 0002:00:06.0: BAR 0: assigned [mem 0xd80000000-0xd83ffffff]^M
pci 0002:00:06.0: BAR 1: assigned [mem 0xd84000000-0xd841fffff]^M
pci 0002:00:02.0: BAR 0: assigned [mem 0xd84200000-0xd84203fff 64bit]^M
pci 0002:00:01.0: BAR 5: assigned [mem 0xd84204000-0xd842041ff]^M
pci 0002:00:03.0: BAR 0: assigned [io  0x1000-0x107f]^M
pci 0002:00:03.0: BAR 1: assigned [mem 0xd84204200-0xd8420427f]^M
pci 0002:00:01.0: BAR 4: assigned [io  0x1080-0x108f]^M
pci 0002:00:01.0: BAR 0: assigned [io  0x1090-0x1097]^M
pci 0002:00:01.0: BAR 2: assigned [io  0x1098-0x109f]^M
pci 0002:00:01.0: BAR 1: assigned [io  0x10a0-0x10a3]^M
pci 0002:00:01.0: BAR 3: assigned [io  0x10a4-0x10a7]^M
pci_bus 0002:00: resource 4 [io  0x0000-0xffff]^M
pci_bus 0002:00: resource 5 [mem 0xd80000000-0xdffffffff]^M
pci_bus 0002:00: resource 6 [mem 0xc0ee00000-0xc0eefffff]^M

bad:

pci 0002:00:06.0: BAR 0: assigned [mem 0xd80000000-0xd83ffffff]^M
pci 0002:00:06.0: BAR 1: assigned [mem 0xd84000000-0xd841fffff]^M
pci 0002:00:02.0: BAR 0: assigned [mem 0xc0ee00000-0xc0ee03fff 64bit]^M
pci 0002:00:01.0: BAR 5: assigned [mem 0xc0ee04000-0xc0ee041ff]^M
pci 0002:00:03.0: BAR 0: assigned [io  0x1000-0x107f]^M
pci 0002:00:03.0: BAR 1: assigned [mem 0xc0ee04200-0xc0ee0427f]^M
pci 0002:00:01.0: BAR 4: assigned [io  0x1080-0x108f]^M
pci 0002:00:01.0: BAR 0: assigned [io  0x1090-0x1097]^M
pci 0002:00:01.0: BAR 2: assigned [io  0x1098-0x109f]^M
pci 0002:00:01.0: BAR 1: assigned [io  0x10a0-0x10a3]^M
pci 0002:00:01.0: BAR 3: assigned [io  0x10a4-0x10a7]^M
pci_bus 0002:00: resource 4 [io  0x0000-0xffff]^M
pci_bus 0002:00: resource 5 [mem 0xc0ee00000-0xc0eefffff]^M
pci_bus 0002:00: resource 6 [mem 0xd80000000-0xdffffffff]^M

Reverting this patch fixes the problem.

Can you please comment out the list_sort()? Seems like the precaution
breaks your system...


Yes, everything works if I re-apply your patch and comment out the
call to list_sort().

Guenter



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