Public bug reported:
[Impact]
PCIe links behind VMD may not be able to reach ASPM L1.2, because PCIe
Link Tolenrence Reporting doesn't get programmed with a sensible value.
[Fix]
Temporarily hardcode LTR value, which is used by Windows, for NVMe
devices behind VMD.
[Test]
With the patch applied, PCIe links can reach ASPM L1.2, hence the entire
Intel SoC can reach deeper power saving state.
[Regression Potential]
This patch targets specifically Intel Tigerlake VMD bridges, so there
won't be any regression since they are not on the market yet.
** Affects: linux (Ubuntu)
Importance: Medium
Status: Confirmed
** Affects: linux-oem-5.6 (Ubuntu)
Importance: Undecided
Status: New
** Affects: linux (Ubuntu Focal)
Importance: Undecided
Status: Won't Fix
** Affects: linux-oem-5.6 (Ubuntu Focal)
Importance: Medium
Status: Confirmed
** Affects: linux (Ubuntu Groovy)
Importance: Medium
Status: Confirmed
** Affects: linux-oem-5.6 (Ubuntu Groovy)
Importance: Undecided
Status: Invalid
** Also affects: linux (Ubuntu Groovy)
Importance: Undecided
Status: New
** Also affects: linux (Ubuntu Focal)
Importance: Undecided
Status: New
** Also affects: linux-oem-5.6 (Ubuntu)
Importance: Undecided
Status: New
** Changed in: linux (Ubuntu Focal)
Status: New => Won't Fix
** Changed in: linux-oem-5.6 (Ubuntu Groovy)
Status: New => Won't Fix
** Changed in: linux-oem-5.6 (Ubuntu Groovy)
Status: Won't Fix => Invalid
** Changed in: linux (Ubuntu Groovy)
Importance: Undecided => Medium
** Changed in: linux-oem-5.6 (Ubuntu Focal)
Importance: Undecided => Medium
** Changed in: linux-oem-5.6 (Ubuntu Focal)
Status: New => Confirmed
** Changed in: linux (Ubuntu Groovy)
Status: New => Confirmed
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https://bugs.launchpad.net/bugs/1896598
Title:
Enable LTR for endpoints behind VMD
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