[PATCH v2 0/3] cxl/pci: Fix the GPF DVSEC setup path

[Guixin Liu <kanie@linux.alibaba.com>]

Three small fixes for the GPF setup path in cxl/core/pci.c, found
while reworking the same area for a downstream backport.

Patch 1 is the one with user-visible impact: on an RCD the GPF DVSEC
lookup takes the port path, so dirty shutdown tracking never arms and
the count stays invalid. The other two deal with error handling and
a full-register rewrite of the phase control register.

Testing on a QEMU CXL topology, with the patched cxl_core hot-swapped
in and the topology re-enumerated. With the phase 1/2 timeout
registers of all four dports (two root ports, two switch downstream
ports) zeroed beforehand, every dport came back at 0x0702 — base 2,
scale 7, the same value the unpatched code writes. So the timeout
write ran on each of them: the read-modify-write of patch 3, through
the error-checked setup of patch 2. With the registers left at their
programmed value instead, the setup takes the "already at max" early
return and writes nothing. Re-enumeration comes up clean, all three
memdevs back.

What QEMU cannot exercise: the topology has no RCD, so the RC_END
branch of patch 1 never ran — though the emulated type-3 devices do
expose the Device GPF DVSEC that the fix selects for a restricted
endpoint. A config write to a live DVSEC does not fail, so the error
paths of patch 2 stayed cold. And the phase control register defines
no non-timeout bits today, so patch 3 lands on the same value the old
full rewrite did.

Changes since v1 [1]:

- Collect the Reviewed-by tags from Jonathan Cameron and Dave Jiang
  for patches 1 and 2 (code unchanged).

- Rework patch 3 to use a pair of FIELD_MODIFY() calls instead of
  clearing and setting the timeout masks by hand, as suggested by
  Jonathan Cameron. The generated code for update_gpf_port_dvsec()
  is identical to the manual version.

[1] https://lore.kernel.org/all/20260922100026.3742401-1-kanie@linux.alibaba.com/

Guixin Liu (3):
  cxl/pci: Use the Device GPF DVSEC for restricted endpoints
  cxl/pci: Program the Port GPF timeouts before caching the DVSEC
  cxl/pci: Update only the Port GPF timeout fields

 drivers/cxl/core/pci.c | 37 +++++++++++++++++++++++++------------
 1 file changed, 25 insertions(+), 12 deletions(-)

-- 
2.43.7