[PATCH i-g-t v4 2/2] tests/intel/xe_pm: Add a check for power management capability

[Kamil Konieczny]

Hi Bernatowicz,,
On 2025-03-19 at 09:14:14 +0100, Bernatowicz, Marcin wrote:
> 
> 
> On 3/19/2025 9:05 AM, Poosa, Karthik wrote:
> > 
> > On 18-03-2025 20:31, Jakub Kolakowski wrote:
> > > Add a check for power management capability of device tested in tests
> > > related to D3 states. Currently if test is started on configuration
> > > that does not support the PM capability it doesn't skip, instead
> > > depending on test it may fail, abort or timeout.
> > > With this change test will skip with a clear message why it did.
> > > 
> > > Cc: Adam Miszczak<adam.miszczak at linux.intel.com>
> > > Cc: Lukasz Laguna<lukasz.laguna at intel.com>
> > > Cc: Marcin Bernatowicz<marcin.bernatowicz at linux.intel.com>
> > > Signed-off-by: Jakub Kolakowski<jakub1.kolakowski at intel.com>
> > > ---
> > >   tests/intel/xe_pm.c | 3 +++
> > >   1 file changed, 3 insertions(+)
> > > 
> > > diff --git a/tests/intel/xe_pm.c b/tests/intel/xe_pm.c
> > > index c2026474d..70f0613fb 100644
> > > --- a/tests/intel/xe_pm.c
> > > +++ b/tests/intel/xe_pm.c
> > > @@ -146,6 +146,9 @@ static void vram_d3cold_threshold_restore(int sig)
> > >   static bool setup_d3(device_t device, enum igt_acpi_d_state state)
> > >   {
> > > +    igt_require_f(igt_has_pci_pm_capability(device.pci_xe),
> > > +              "PCI power management capability not found\n");
> > 
> > Hi Jakub,
> > 
> > As per PCIe Base spec, all PCI Express Functions are required to support
> > PCI Power Management Capability.
> > 
> > Only legacy PCI devices wouldn't have it.
> > 
> > Can you share details of failures without this capability.
> > 
> > All Xe supported GPUs are PCIe complaint, this check may not be needed
> > at all.
> 
> This happens for runs with Virtual Function (VF) passed to Virtual Machine
> (VM).
> 
> "9.6 SR-IOV Power Management
> This section defines the PCI Express SR-IOV power management capabilities
> and protocols.
> The Power Management Capability is required for PFs as described in Chapter
> 5 .
> For VFs, the Power Management Capability is optional."

Can we add this explanation as a comment in code?
imho one sentence like:

PCIe power management is mandatory for real hardware devices,
for SR-IOV VFs it is optional.

or something like that?

Regards,
Kamil

> 
> --
> marcin
> 
> > 
> > 
> > > +
> > >       dpms_on_off(device, DRM_MODE_DPMS_OFF);
> > >       /*
>