[24.04_linux-nvidia-6.17-next] PCI: mirror PI7C9X3G606GPC Port 4 BAR0

[nirmoy]

Summary

• Add a PCI final/resume quirk for Pericom/Diodes PI7C9X3G606GPC to mirror the upstream BAR0 value into downstream Port 4 BAR0.
• Scope the WAR to the Diodes-confirmed OS-visible Tile0/P4 mapping: upstream bus + 1, device 04, function 0.
• Port 4 BAR0 may read back as zero through normal PCI config space even after a successful write, so the quirk rewrites BAR0 whenever it runs.

Validation

• Built 6.17.0-1018-nvidia-64k test debs from this WAR path.
• Expected dmesg when the WAR runs:

pci 0002:a2:04.0: wrote upstream BAR 0 0x10c00000 to Port 4 BAR 0 for PI7C9X3G606GPC workaround

• The BAR value is platform/boot dependent. In the Quark test run, Linux reassigned upstream BAR0 for 0002:a1:00.0 from 0x10300000 to 0x10c00000, then the quirk wrote 0x10c00000 to 0002:a2:04.0 Port 4 BAR0.
• Normal config-space readback of Port 4 BAR0 still returns 0 on this device, so setpci readback is not a valid failure signal for the WAR.
• A Diodes-provided BMC/I2C debug readback sequence returned non-zero Port 4 BAR0 bytes, 0x10 0xc0 0x00 0x00, matching 0x10c00000. That sequence uses special CPED/CDEP programming and is not a supported production validation path on this platform, so further validation should avoid it.

Fresh validation with the exact rebased PR package set is still pending.

References

Launchpad: https://bugs.launchpad.net/ubuntu/+source/linux-nvidia-6.17/+bug/2154457

NVBug: https://nvbugspro.nvidia.com/bug/6205517
NVBug: https://nvbugspro.nvidia.com/bug/6134331

Test artifacts: http://baseos-internal-tools.nvidia.com:8003/

[nirmoy]

Boro review

Latest watcher review: open review

Head: 5edb468a3760

This comment is maintained by nv-pr-bot. It is updated when the GitHub watcher publishes a newer review.

[github-actions]

PR Validation Report

Patchscan ✅ No Missing Fixes

All cherry-picked commits checked — no missing upstream fixes found.

PR Lint ✅ All checks passed

Details

Checking 1 commits...

Cherry-pick digest:
┌──────────────┬──────────────────────────────────────────────────────────────────┬────────────┬─────────┬───────────────────────────┐
│ Local        │ Referenced upstream / Patch subject                              │ Patch-ID   │ Subject │ SoB chain                 │
├──────────────┼──────────────────────────────────────────────────────────────────┼────────────┼─────────┼───────────────────────────┤
│ 5edb468a3760 │ [SAUCE] pci: quirks: mirror pi7c9x3g606gpc port 4 bar0           │ N/A        │ N/A     │ nirmoyd                   │
└──────────────┴──────────────────────────────────────────────────────────────────┴────────────┴─────────┴───────────────────────────┘

Lint: all checks passed.

[nvidia-bfigg]

Does this PR need to be applied to the 6.18 reference kernel as well?

[nvidia-bfigg]

Do you have tests (scripts) which can verify this patch set is applied and working?

[nirmoy]

Hi @nvidia-bfigg

Does this PR need to be applied to the 6.18 reference kernel as well?

Yes, we need that for 6.18 too. I will create a PR for that as well

Do you have tests (scripts) which can verify this patch set is applied and working?
The kernel WAR will be always applied at the boot time because config read of the effected port always return 0 so we should see the in the dmesg wrote upstream BAR 0 %#x to Port 4 BAR 0 for PI7C

[nvidia-bfigg]

Hi @nvidia-bfigg

Does this PR need to be applied to the 6.18 reference kernel as well?

Yes, we need that for 6.18 too. I will create a PR for that as well

Do you have tests (scripts) which can verify this patch set is applied and working?
The kernel WAR will be always applied at the boot time because config read of the effected port always return 0 so we should see the in the dmesg wrote upstream BAR 0 %#x to Port 4 BAR 0 for PI7C

So if the patch is not applied to the kernel that message will not be in the dmesg. We should have a test that verifies that message is in the dmesg or the test should fail that the patch has not been applied, correct?

[nirmoy]

Hi @nvidia-bfigg

Does this PR need to be applied to the 6.18 reference kernel as well?

Yes, we need that for 6.18 too. I will create a PR for that as well

Do you have tests (scripts) which can verify this patch set is applied and working?
The kernel WAR will be always applied at the boot time because config read of the effected port always return 0 so we should see the in the dmesg wrote upstream BAR 0 %#x to Port 4 BAR 0 for PI7C

So if the patch is not applied to the kernel that message will not be in the dmesg. We should have a test that verifies that message is in the dmesg or the test should fail that the patch has not been applied, correct?

Yes, ACK we should have a test may be a greenlit one to check the dmesg to verify the patch.