PCI: Fix restoring BARs on BAR resize rollback path

BAR resize operation is implemented in the pci_resize_resource() and
pbus_reassign_bridge_resources() functions. pci_resize_resource() can be
called either from __resource_resize_store() from sysfs or directly by the
driver for the Endpoint Device.

The pci_resize_resource() requires that caller has released the device
resources that share the bridge window with the BAR to be resized as
otherwise the bridge window is pinned in place and cannot be changed.

pbus_reassign_bridge_resources() rolls back resources if the resize
operation fails, but rollback is performed only for the bridge windows.
Because releasing the device resources are done by the caller of the BAR
resize interface, these functions performing the BAR resize do not have
access to the device resources as they were before the resize.

pbus_reassign_bridge_resources() could try __pci_bridge_assign_resources()
after rolling back the bridge windows as they were, however, it will not
guarantee the resource are assigned due to differences in how FW and the
kernel assign the resources (alignment of the start address and tail).

To perform rollback robustly, the BAR resize interface has to be altered to
also release the device resources that share the bridge window with the BAR
to be resized.

Also, remove restoring from the entries failed list as saved list should
now contain both the bridge windows and device resources so the extra
restore is duplicated work.

Some drivers (currently only amdgpu) want to prevent releasing some
resources. Add exclude_bars param to pci_resize_resource() and make amdgpu
pass its register BAR (BAR 2 or 5), which should never be released during
resize operation. Normally 64-bit prefetchable resources do not share a
bridge window with the 32-bit only register BAR, but there are various
fallbacks in the resource assignment logic which may make the resources
share the bridge window in rare cases.

This change (together with the driver side changes) is to counter the
resource releases that had to be done to prevent resource tree corruption
in the ("PCI: Release assigned resource before restoring them") change. As
such, it likely restores functionality in cases where device resources were
released to avoid resource tree conflicts which appeared to be "working"
when such conflicts were not correctly detected by the kernel.

Reported-by: Simon Richter <Simon.Richter@hogyros.de>
Link: https://lore.kernel.org/linux-pci/f9a8c975-f5d3-4dd2-988e-4371a1433a60@hogyros.de/
Reported-by: Alex Bennée <alex.bennee@linaro.org>
Link: https://lore.kernel.org/linux-pci/874irqop6b.fsf@draig.linaro.org/
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
[bhelgaas: squash amdgpu BAR selection from
https://lore.kernel.org/r/20251114103053.13778-1-ilpo.jarvinen@linux.intel.com]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Tested-by: Alex Bennée <alex.bennee@linaro.org> # AVA, AMD GPU
Reviewed-by: Christian König <christian.koenig@amd.com>
Link: https://patch.msgid.link/20251113162628.5946-7-ilpo.jarvinen@linux.intel.com

1 files changed, 3 insertions, 1 deletions

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
index 7a899fb4de29..bf0bc38e1c47 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
@@ -1736,7 +1736,9 @@ int amdgpu_device_resize_fb_bar(struct amdgpu_device *adev)
 
 	pci_release_resource(adev->pdev, 0);
 
-	r = pci_resize_resource(adev->pdev, 0, rbar_size);
+	r = pci_resize_resource(adev->pdev, 0, rbar_size,
+				(adev->asic_type >= CHIP_BONAIRE) ? 1 << 5
+								  : 1 << 2);
 	if (r == -ENOSPC)
 		dev_info(adev->dev,
 			 "Not enough PCI address space for a large BAR.");