Re: [PATCH 4/6] ACPI: Execute platform _OSC also with query bit clear

[Mika Westerberg <mika.westerberg@linux.intel.com>]

On Tue, Jan 26, 2021 at 10:43:32PM +0000, Limonciello, Mario wrote:
> > I would put that information into the changelog.
> 
> Thanks, @Mika Westerberg can you collapse that in when you re-spin the
> series?

Sure.

> > 
> > Moreover, have you looked at acpi_pci_osc_control_set()?
> > 
> > What it does is analogous to what you are proposing, but a bit
> > different, and I would like to preserve consistency between _OSC use
> > cases.
> > 
> > So would it be possible to adjust the _SB _OSC evaluation flow to
> > follow the PCI _OSC one?  That is, if any control bits are there, pass
> > them along with the last evaluation of _OSC with the query flag clear.
> > Or is the latter defective and if so then why?
> 
> Basically the only difference is another line cloning OSC_CONTROL_DWORD from
> capbuf_ret to capbuf?
> 
> Yes, this actually sounds like it better adheres to the spec to me.
> 
> Quoting spec:
> " If the OS is granted control of a feature in the Control Field in one call to
> _OSC, then it must preserve the set state of that bit (requesting that feature)
> in all subsequent calls."

However, the platform wide _OSC does not actually have this
OSC_CONTROL_DWORD at all ;-)

I think what we do in this patch is already equivalent to what the PCI
_OSC is doing:

  1. Query bit set _OSC
  2. Take the returned OSC_SUPPORT_DWORD buffer and
  3. Pass it to the _OSC with query bit clear.

I may be missing something, though.