Message-ID: <01eb7d40-f5b5-4ec5-b390-a5c042c30aff@roeck-us.net>
Date: Mon, 31 Mar 2025 19:35:20 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
Cc: Bjorn Helgaas <bhelgaas@...gle.com>, linux-pci@...r.kernel.org,
	Michał Winiarski <michal.winiarski@...el.com>,
	Igor Mammedov <imammedo@...hat.com>, linux-kernel@...r.kernel.org,
	Mika Westerberg <mika.westerberg@...ux.intel.com>
Subject: Re: [PATCH 24/25] PCI: Perform reset_resource() and build fail list
 in sync

Hi,

On Mon, Dec 16, 2024 at 07:56:31PM +0200, Ilpo Järvinen wrote:
> Resetting resource is problematic as it prevent attempting to allocate
> the resource later, unless something in between restores the resource.
> Similarly, if fail_head does not contain all resources that were reset,
> those resource cannot be restored later.
> 
> The entire reset/restore cycle adds complexity and leaving resources
> into reseted state causes issues to other code such as for checks done
> in pci_enable_resources(). Take a small step towards not resetting
> resources by delaying reset until the end of resource assignment and
> build failure list (fail_head) in sync with the reset to avoid leaving
> behind resources that cannot be restored (for the case where the caller
> provides fail_head in the first place to allow restore somewhere in the
> callchain, as is not all callers pass non-NULL fail_head).
> 
> The Expansion ROM check is temporarily left in place while building the
> failure list until the upcoming change which reworks optional resource
> handling.
> 
> Ideally, whole resource reset could be removed but doing that in a big
> step would make the impact non-tractable due to complexity of all
> related code.
> 
> Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>

With this patch in the mainline kernel, all mips:boston qemu emulations
fail when running a 64-bit little endian configuration (64r6el_defconfig).

The problem is that the PCI based IDE/ATA controller is not initialized.
There are a number of pci error messages.

pci_bus 0002:01: extended config space not accessible
pci 0002:01:00.0: [8086:2922] type 00 class 0x010601 conventional PCI endpoint
pci 0002:01:00.0: BAR 4 [io  0x0000-0x001f]
pci 0002:01:00.0: BAR 5 [mem 0x00000000-0x00000fff]
pci 0002:00:00.0: PCI bridge to [bus 01-ff]
pci_bus 0002:01: busn_res: [bus 01-ff] end is updated to 01
pci 0002:00:00.0: bridge window [mem 0x16000000-0x160fffff]: assigned
pci 0002:00:00.0: bridge window [mem size 0x00100000 64bit pref]: can't assign; no space
pci 0002:00:00.0: bridge window [mem size 0x00100000 64bit pref]: failed to assign
pci 0002:00:00.0: bridge window [io  size 0x1000]: can't assign; no space
pci 0002:00:00.0: bridge window [io  size 0x1000]: failed to assign
pci 0002:00:00.0: bridge window [mem size 0x00100000]: can't assign; bogus alignment
pci 0002:00:00.0: bridge window [mem 0x16000000-0x160fffff 64bit pref]: assigned
pci 0002:00:00.0: bridge window [io  size 0x1000]: can't assign; no space
pci 0002:00:00.0: bridge window [io  size 0x1000]: failed to assign
pci 0002:01:00.0: BAR 5 [mem size 0x00001000]: can't assign; no space
pci 0002:01:00.0: BAR 5 [mem size 0x00001000]: failed to assign
pci 0002:01:00.0: BAR 4 [io  size 0x0020]: can't assign; no space
pci 0002:01:00.0: BAR 4 [io  size 0x0020]: failed to assign
pci 0002:01:00.0: BAR 5 [mem size 0x00001000]: can't assign; no space
pci 0002:01:00.0: BAR 5 [mem size 0x00001000]: failed to assign
pci 0002:01:00.0: BAR 4 [io  size 0x0020]: can't assign; no space
pci 0002:01:00.0: BAR 4 [io  size 0x0020]: failed to assign
pci 0002:00:00.0: PCI bridge to [bus 01]
pci 0002:00:00.0:   bridge window [mem 0x16000000-0x160fffff 64bit pref]
pci_bus 0002:00: Some PCI device resources are unassigned, try booting with pci=realloc
pci_bus 0002:00: resource 4 [mem 0x16000000-0x160fffff]
pci_bus 0002:01: resource 2 [mem 0x16000000-0x160fffff 64bit pref]
...
pci 0002:00:00.0: enabling device (0000 -> 0002)
ahci 0002:01:00.0: probe with driver ahci failed with error -12

Bisect points to this patch. Reverting it together with "PCI: Rework
optional resource handling" fixes the problem. For comparison, after
reverting the offending patches, the log messages are as follows.

pci_bus 0002:00: root bus resource [bus 00-ff]
pci_bus 0002:00: root bus resource [mem 0x16000000-0x160fffff]
pci 0002:00:00.0: [10ee:7021] type 01 class 0x060400 PCIe Root Complex Integrated Endpoint
pci 0002:00:00.0: PCI bridge to [bus 00]
pci 0002:00:00.0:   bridge window [io  0x0000-0x0fff]
pci 0002:00:00.0:   bridge window [mem 0x00000000-0x000fffff]
pci 0002:00:00.0:   bridge window [mem 0x00000000-0x000fffff 64bit pref]
pci 0002:00:00.0: enabling Extended Tags
pci 0002:00:00.0: bridge configuration invalid ([bus 00-00]), reconfiguring
pci_bus 0002:01: extended config space not accessible
pci 0002:01:00.0: [8086:2922] type 00 class 0x010601 conventional PCI endpoint
pci 0002:01:00.0: BAR 4 [io  0x0000-0x001f]
pci 0002:01:00.0: BAR 5 [mem 0x00000000-0x00000fff]
pci 0002:00:00.0: PCI bridge to [bus 01-ff]
pci_bus 0002:01: busn_res: [bus 01-ff] end is updated to 01
pci 0002:00:00.0: bridge window [mem 0x16000000-0x160fffff]: assigned
pci 0002:00:00.0: bridge window [mem size 0x00100000 64bit pref]: can't assign; no space
pci 0002:00:00.0: bridge window [mem size 0x00100000 64bit pref]: failed to assign
pci 0002:00:00.0: bridge window [io  size 0x1000]: can't assign; no space
pci 0002:00:00.0: bridge window [io  size 0x1000]: failed to assign
pci 0002:01:00.0: BAR 5 [mem 0x16000000-0x16000fff]: assigned
pci 0002:01:00.0: BAR 4 [io  size 0x0020]: can't assign; no space
pci 0002:01:00.0: BAR 4 [io  size 0x0020]: failed to assign
pci 0002:00:00.0: PCI bridge to [bus 01]
pci 0002:00:00.0:   bridge window [mem 0x16000000-0x160fffff]
pci_bus 0002:00: Some PCI device resources are unassigned, try booting with pci=realloc
pci_bus 0002:00: resource 4 [mem 0x16000000-0x160fffff]
pci_bus 0002:01: resource 1 [mem 0x16000000-0x160fffff]
...
pci 0002:00:00.0: enabling device (0000 -> 0002)
ahci 0002:01:00.0: enabling device (0000 -> 0002)
ahci 0002:01:00.0: AHCI vers 0001.0000, 32 command slots, 1.5 Gbps, SATA mode
ahci 0002:01:00.0: 6/6 ports implemented (port mask 0x3f)
ahci 0002:01:00.0: flags: 64bit ncq only

Bisect log is attached for reference.

Guenter
---
# bad: [609706855d90bcab6080ba2cd030b9af322a1f0c] Merge tag 'trace-latency-v6.15-3' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace
# good: [acb4f33713b9f6cadb6143f211714c343465411c] Merge tag 'm68knommu-for-v6.15' of git://git.kernel.org/pub/scm/linux/kernel/git/gerg/m68knommu
git bisect start 'HEAD' 'acb4f33713b9'
# good: [cf05922d63e2ae6a9b1b52ff5236a44c3b29f78c] Merge tag 'drm-intel-gt-next-2025-03-12' of https://gitlab.freedesktop.org/drm/i915/kernel into drm-next
git bisect good cf05922d63e2ae6a9b1b52ff5236a44c3b29f78c
# bad: [93d52288679e29aaa44a6f12d5a02e8a90e742c5] Merge tag 'backlight-next-6.15' of git://git.kernel.org/pub/scm/linux/kernel/git/lee/backlight
git bisect bad 93d52288679e29aaa44a6f12d5a02e8a90e742c5
# bad: [e5e0e6bebef3a21081fd1057c40468d4cff1a60d] Merge tag 'v6.15-p1' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6
git bisect bad e5e0e6bebef3a21081fd1057c40468d4cff1a60d
# bad: [dea140198b846f7432d78566b7b0b83979c72c2b] Merge branch 'pci/misc'
git bisect bad dea140198b846f7432d78566b7b0b83979c72c2b
# bad: [a113afb84ae63ec4c893bc3204945ef6f3bb89f7] Merge branch 'pci/endpoint'
git bisect bad a113afb84ae63ec4c893bc3204945ef6f3bb89f7
# good: [a7a8e7996c1c114b50df5599229b1e7be38be3db] Merge branch 'pci/reset'
git bisect good a7a8e7996c1c114b50df5599229b1e7be38be3db
# bad: [7d4bcc0f2631e4ee10b5bcfff24a423d1c3c02a3] PCI: Move resource reassignment func declarations into pci/pci.h
git bisect bad 7d4bcc0f2631e4ee10b5bcfff24a423d1c3c02a3
# good: [acba174d2e754346c07578ad2220258706a203e2] PCI: Use while loop and break instead of gotos
git bisect good acba174d2e754346c07578ad2220258706a203e2
# good: [8884b5637b794ae541e8d6fb72102b1d8dba2b8d] PCI: Add debug print when releasing resources before retry
git bisect good 8884b5637b794ae541e8d6fb72102b1d8dba2b8d
# bad: [5af473941b56189423a7d16c05efabaf77299847] PCI: Increase Resizable BAR support from 512 GB to 128 TB
git bisect bad 5af473941b56189423a7d16c05efabaf77299847
# bad: [96336ec702643aec2addb3b1cdb81d687fe362f0] PCI: Perform reset_resource() and build fail list in sync
git bisect bad 96336ec702643aec2addb3b1cdb81d687fe362f0
# good: [e89df6d2beae847e931d84a190b192dfac41eba7] PCI: Use res->parent to check if resource is assigned
git bisect good e89df6d2beae847e931d84a190b192dfac41eba7
# first bad commit: [96336ec702643aec2addb3b1cdb81d687fe362f0] PCI: Perform reset_resource() and build fail list in sync

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