Comment 18 for bug 1803179

(In reply to Lv Zheng from comment #8)
> Do you mean it's already long enough (95.7ms) for this case, and waiting
> longer won't solve the issue?

That would be the theoretical delay. In practice, I have several seconds of processing due to ACPI debug logging (ACPI_NAMESPACE, ACPI_DB_NAMES). The logs stop after 46 seconds, maybe because I used SysRq+B for a forced reboot (reset).

> I'm not a PCI expert. So let me ask.
> From the following AML, RTLK/LNKS belong to a PCI register space:
> OperationRegion (SANV, SystemMemory, 0x5FF9BD98, 0x0135)
> Field (SANV, AnyAcc, Lock, Preserve)
> {
[snip]
> Can you infer what it is from the above AML?

XBAS is the PCIe MMIO Base Address register. I guessed that "RTLK" means "Retrain Link" (see PCIe spec 7.8.7 Link Control Register) and that "LNKS" means PCIe Link speed. I posted these on:

https://github.com/Lekensteyn/acpi-stuff/blob/master/Clevo-P651RA/notes.txt

(In reply to Lv Zheng from comment #9)
> It looks like AML code in PGON prior than this loop should always make the
> condition true. What the platform need to do is to wait.
> So IMO, the code prior than this loop is more important for root causing
> this issue.

The loop is indeed just a consequence, the root cause is due to the difference between invoking the "LKEN" code (problematic, see line 120 of notes.txt) and the fallback code (see line 141 of notes.txt).

However I am quite at loss on why it would be so significant. Note that I am no PCI expert either, the notes were based on the PCIe spec, ACPI tables and lots of guesswork.

Do you need more info?