[PATCH v3] drm/i915: Flush WC GGTT only on required platforms

[Andi Shyti]

Hi Nirmoy,

> > > gen8_ggtt_invalidate() is only needed for limited set of platforms
> > > where GGTT is mapped as WC. This was added as way to fix WC based GGTT in
> > > commit 0f9b91c754b7 ("drm/i915: flush system agent TLBs on SNB") and
> > > there are no reference in HW docs that forces us to use this on non-WC
> > > backed GGTT.
> > > 
> > > This can also cause unwanted side-effects on XE_HP platforms where
> > > GFX_FLSH_CNTL_GEN6 is not valid anymore.
> > > 
> > > v2: Add a func to detect wc ggtt detection (Ville)
> > > v3: Improve commit log and add reference commit (Daniel)
> > > 
> > > Fixes: d2eae8e98d59 ("drm/i915/dg2: Drop force_probe requirement")
> > I'm wondering if this is the right Fixes, though. Should this
> > rather be:
> > 
> > Fixes: 6266992cf105 ("drm/i915/gt: remove GRAPHICS_VER == 10")
> 
> Hard to find a real Fixes for this. I just want to backport this to dg2
> where we can have unwanted side-effects.

yes, this piece of code has moved around enough so to make it
diffuclt to track its origin.

I think the one I found should be the correct one, but the dg2
force probe removeal can also become a placeholder for DG2 fixes.

I won't complain.

Andi