[Public]
> I would do
>
> if (capbuf[OSC_SUPPORT_DWORD] == capbuf_ret[OSC_SUPPORT_DWORD])
> capbuf[OSC_QUERY_DWORD] = 0;
> else
> capbuf[OSC_SUPPORT_DWORD] &= capbuf_ret[OSC_SUPPORT_DWORD];
>
> so that the loop terminates even if the firmware does strange things
> and then it would only be necessary to check capbuf[OSC_QUERY_DWORD]
> in the loop termination condition.
>
> Would that work?
>
I think it will. I'll try it and send up a v7 if so.
> > + kfree(context.ret.pointer);
> > + } while (capbuf[OSC_QUERY_DWORD] &&
> capbuf[OSC_SUPPORT_DWORD]);
> >
> > - /* Now run _OSC again with query flag clear */
> > - capbuf[OSC_QUERY_DWORD] = 0;
> > + /*
> > + * Avoid problems with BIOS dynamically loading tables by indicating
> > + * support for CPPC even if it was masked.
>
> What exactly do you mean by "BIOS dynamically loading tables"?
As mentioned in commit 159d8c274fd9:
On certain systems the BIOS loads SSDT tables dynamically based on the
capabilities the OS claims to support. However, on these systems the
_OSC actually clears some of the bits (under certain conditions) so what
happens is that now when we call the _OSC twice the second time we pass
the cleared values and that results errors like below to appear on the
system log:
ACPI BIOS Error (bug): Could not resolve symbol [\_PR.PR00._CPC], AE_NOT_FOUND (20210105/psargs-330)
ACPI Error: Aborting method \_PR.PR01._CPC due to previous error (AE_NOT_FOUND) (20210105/psparse-529)
This block is to avoid regressing that again by forcing it on these systems.
>
> > + */
> > +#ifdef CONFIG_X86
> > + if (boot_cpu_has(X86_FEATURE_HWP)) {
> > + capbuf[OSC_SUPPORT_DWORD] |= OSC_SB_CPC_SUPPORT;
> > + capbuf[OSC_SUPPORT_DWORD] |= OSC_SB_CPCV2_SUPPORT;
> > + }
> > +#endif
> >
> > + /* Now run _OSC again with query flag clear */
> > if (ACPI_FAILURE(acpi_run_osc(handle, &context)))
> > return;
> >
> > --
> > 2.34.1
> >
