[PATCH 0/1][SRU][OEM-5.6/G] UBUNTU: SAUCE: PCI/ASPM: VMD: add ASPM quirk for 8086:a0bc

[You-Sheng Yang]

BugLink: https://bugs.launchpad.net/bugs/1893194

[Impact]

One VMD equipped platform has another PCI bridge with PCI ID [8086:a0bc]
that is not already in Ubuntu sauced PCI_DEV_FLAGS_ENABLE_ASPM list from
bug 1889384. Link Capability Register shows ASPM L1 supported, but has
ASPM Disabled in Link Control status.

10000:e0:1c.4 PCI bridge [0604]: Intel Corporation Device [8086:a0bc]
(rev 20) (prog-if 00 [Normal decode])
        ...
 Capabilities: [40] Express (v2) Root Port (Slot+), MSI 00
  ...
  LnkCap: Port #5, Speed 8GT/s, Width x4, ASPM L1, Exit Latency L1 <16us
   ClockPM- Surprise- LLActRep+ BwNot+ ASPMOptComp+
  LnkCtl: ASPM Disabled; RCB 64 bytes Disabled- CommClk+
   ExtSynch- ClockPM- AutWidDis- BWInt- AutBWInt-

[Fix]

Add 8086:a0bc to PCI_DEV_FLAGS_ENABLE_ASPM quirk list introduced in Bug
1889384. The proposed fix for Bug 1889384 is still under review on
linux-pci mailing list
https://lore.kernel.org/linux-pci/20200821123222.32093-1-kai.heng.feng@canonical.com/.

[Test Case]

Use `sudo lspci -vvnnxxx` to check LnkCap/LnkCtl registers. Make sure it
becomes:

  LnkCtl: ASPM Enabled, ...

[Regression Potential]

Low. Like the previous fix in bug 1889384, this add the device ID who
declaring capable of link ASPM support to the quirk list.

You-Sheng Yang (1):
  UBUNTU: SAUCE: PCI/ASPM: VMD: add ASPM quirk for 8086:a0bc

 drivers/pci/quirks.c | 1 +
 1 file changed, 1 insertion(+)

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2.27.0