[PATCH v1] drm/i915/dg2: enable G8 with a workaround

[Matt Roper]

On Wed, Oct 09, 2024 at 07:42:40PM +0300, Raag Jadav wrote:
> On Wed, Oct 09, 2024 at 04:05:20PM +0300, Jani Nikula wrote:
> > On Wed, 09 Oct 2024, Raag Jadav <raag.jadav at intel.com> wrote:
> > > On Tue, Oct 08, 2024 at 08:24:42PM +0300, Jani Nikula wrote:
> > >> On Mon, 07 Oct 2024, Raag Jadav <raag.jadav at intel.com> wrote:
> > >> > +
> > >> > +/* Wa_14022698589:dg2 */
> > >> > +static void intel_enable_g8(struct intel_uncore *uncore)
> > >> > +{
> > >> > +	if (IS_DG2(uncore->i915)) {
> > >> > +		switch (INTEL_DEVID(uncore->i915)) {
> > >> 
> > >> Even using INTEL_DEVID() is a no-go. There are currently four users, and
> > >> even some of them are too much.
> > >> 
> > >> We try hard to abstract this stuff at a higher level, and there must be
> > >> zero direct PCI ID checks in code other than the table driven device
> > >> identification. Otherwise it's just impossible to figure out where we do
> > >> platform specific stuff for each platform.
> > >
> > > Even if we use pci_match_id(), we'd need an explicit list to match against.
> > 
> > Well, we don't use that for individual workarounds or hacks either. When
> > you think of using something like that, see what git grep says.
> > 
> > > Any better way?
> > 
> > You probably need to turn it into another subplatform, and add it in
> > intel_device_info.c. You're probably going to need to rehash the
> > INTEL_DG2_*_IDS PCI ID macros too. That's how we tell platforms apart at
> > the PCI ID granularity.
> 
> Which would be controversial since the ids span across existing subplatforms,
> which we don't want to break.

A single platform can belong to multiple subplatforms.  So it's fine,
for example, for a specific device ID to belong to both the DG2-G11
subplatform and the "do extra G8 stuff" subplatform.  You'll just need
to make sure you separate out the G8 subplatform into a separate 'if'
statement rather than trying to include it in the current if/else
ladder.


Matt

> 
> Don't we have quirk mask thing like display?
> 
> Raag

-- 
Matt Roper
Graphics Software Engineer
Linux GPU Platform Enablement
Intel Corporation