Re: [PATCH 0/4] PCI/DPC: Decide DPC ownership with host_bridge->native_dpc

[Kuppuswamy Sathyanarayanan]

Hi Bjorn,

On 10/12/2026 4:20 PM, Bjorn Helgaas wrote:
> On Wed, Oct 07, 2026 at 09:58:36AM -0700, Kuppuswamy Sathyanarayanan wrote:
>> This series makes host_bridge->native_dpc the single decider for whether
>> Linux uses DPC, as Bjorn asked during the review of "Simplify PCIe native
>> ownership".
>>
>>   https://lore.kernel.org/r/20261001221408.GA2731929@bhelgaas
>>
>> Today the DPC service binds on host_bridge->native_aer, AER availability
>> and "pcie_ports=dpc-native".  host_bridge->native_dpc is only consulted
>> by pci_dpc_recovered().  After this series, native_dpc is the end result
>> of everything that decides DPC ownership, and portdrv binds the DPC
>> service on it.
>>
>> The series applies on top of two others:
>>
>>   - pci/portdrv, which has patches 1-3 of v15 of "Simplify PCIe native
>>     ownership".  They fold "pcie_ports=native" and "pcie_ports=dpc-native"
>>     into the _OSC control mask, so native_dpc already reflects the
>>     command line.
>>
>>     https://lore.kernel.org/r/20261002211828.1293177-1-sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx
>>
>>   - Lukas's "Error reporting for AER-incapable devices".  It removes the
>>     AER Capability requirement from the DPC driver.
>>
>>     https://lore.kernel.org/r/cover.1790531238.git.lukas@xxxxxxxxx
> 
> My impression was that Lukas planned to tweak a couple things in that
> series, e.g., https://lore.kernel.org/all/arltOHrdHdokyfC9@xxxxxxxxx
> 
> Does this actually depend on Lukas' series?  If so, can we include the
> relevant patch here?

It applies and builds on pci/portdrv without Lukas's series. It only
depends on his first two patches, which are DPC fixes. The rework he
mentioned is for patches 6 and 7, and this series doesn't need those.

  PCI/DPC: Avoid access to non-existent AER capability
  PCI/DPC: Reinstate support for AER-incapable ports

dpc_probe() still returns -ENOTSUPP unless the OS owns AER or
"pcie_ports=dpc-native" is given. Without Lukas's patch 2, portdrv
creates the DPC service from native_dpc, but dpc_probe() then rejects it
when firmware grants DPC and retains AER. So the change in patch 4 would
not take effect. Lukas's patch 2 needs his patch 1, because the DPC
driver uses the AER capability without checking that it exists.

If Lukas has no objections, I can include Lukas 2 patches part of v2.

> 
>> Patch 1 removes CONFIG_PCIE_EDR, which was another knob in deciding
>> whether to request DPC control in _OSC.
>>
>> Patch 2 stops requiring pci_aer_available() to bind the DPC service,
>> since the DPC driver does not depend on MSI or on the AER driver.
>>
>> Patch 3 requests DPC control only together with AER control, as PCI
>> Firmware r3.3, sec 4.5.2.4, requires.
>>
>> Patch 4 binds the DPC service on host_bridge->native_dpc and logs a
>> message when the OS assumes DPC control that _OSC did not grant.
>>
>> Kuppuswamy Sathyanarayanan (4):
>>   PCI/EDR: Remove CONFIG_PCIE_EDR
>>   PCI/portdrv: Don't require AER to bind DPC service
>>   PCI/ACPI: Request DPC control only together with AER control
>>   PCI/portdrv: Bind DPC service based on host_bridge->native_dpc
>>
>>  drivers/acpi/pci_root.c    | 26 +++++++++++++++++++++++---
>>  drivers/pci/pcie/Kconfig   |  9 ---------
>>  drivers/pci/pcie/Makefile  |  5 ++++-
>>  drivers/pci/pcie/dpc.c     |  5 +++--
>>  drivers/pci/pcie/portdrv.c |  7 +------
>>  include/linux/pci-acpi.h   |  4 ++--
>>  6 files changed, 33 insertions(+), 23 deletions(-)
>>
>>
>> base-commit: 4fe37866b0d92cdc45b62954a76489a9d9f8bd73
>> prerequisite-patch-id: e0eafcb39f15c38f3acfa601dfce07a6f0832ce1
>> prerequisite-patch-id: 83e8185612e785fad80790d4a0c20fa68ab12ce7
>> prerequisite-patch-id: 8e9e2b06f55249ff57c7d7f43918ee82f79d1450
>> prerequisite-patch-id: 78ad13a1c423c3ee50122237c4bd0fdedf2d1e00
>> prerequisite-patch-id: 0c4b9d46eea86635c431382aef2bf576a3bb5691
>> prerequisite-patch-id: 2d1a35309e750427352c6fe0d9bb62c4453c6252
>> prerequisite-patch-id: c1ed9c8ac6123e0a65ae0d7ba3183dd46477edf7
>> -- 
>> 2.43.0
>>

-- 
Sathyanarayanan Kuppuswamy
Linux Kernel Developer