On Mon, Mar 07, 2022 at 10:32:36AM +0000, Matthew Auld wrote:
> On 04/03/2022 19:33, Ville Syrjälä wrote:
> > On Fri, Mar 04, 2022 at 05:23:32PM +0000, Matthew Auld wrote:
> >> The offset we get looks to be the exact start of DSM, but the
> >> inital_plane_vma expects the address to be relative.
> >>
> >> Signed-off-by: Matthew Auld <matthew.auld@xxxxxxxxx>
> >> Cc: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx>
> >> ---
> >> .../drm/i915/display/intel_plane_initial.c | 22 +++++++++++++++----
> >> 1 file changed, 18 insertions(+), 4 deletions(-)
> >>
> >> diff --git a/drivers/gpu/drm/i915/display/intel_plane_initial.c b/drivers/gpu/drm/i915/display/intel_plane_initial.c
> >> index f797fcef18fc..b39d3a8dfe45 100644
> >> --- a/drivers/gpu/drm/i915/display/intel_plane_initial.c
> >> +++ b/drivers/gpu/drm/i915/display/intel_plane_initial.c
> >> @@ -56,10 +56,24 @@ initial_plane_vma(struct drm_i915_private *i915,
> >> if (!mem || plane_config->size == 0)
> >> return NULL;
> >>
> >> - base = round_down(plane_config->base,
> >> - I915_GTT_MIN_ALIGNMENT);
> >> - size = round_up(plane_config->base + plane_config->size,
> >> - mem->min_page_size);
> >> + base = plane_config->base;
> >> + if (IS_DGFX(i915)) {
> >> + /*
> >> + * On discrete the base address should be somewhere in LMEM, but
> >> + * depending on the size of LMEM the base address might
> >> + * intersect with the start of DSM, like on DG1, in which case
> >> + * we need the relative address. In such cases we might also
> >> + * need to choose between inital fb vs fbc, if space is limited.
> >> + *
> >> + * On future discrete HW, like DG2, we should be able to just
> >> + * allocate directly from LMEM, due to larger LMEM size.
> >> + */
> >> + if (base >= i915->dsm.start)
> >> + base -= i915->dsm.start;
> >
> > Subsequent code expects the object to actually be inside stolen.
> > If that is not the case we should just give up.
>
> Thanks for taking a look at this. Is that subsequent code outside
> initial_plane_vma()? In the next patch this is now using LMEM directly
> for dg2. Would that blow up somewhere else?
It uses i915_gem_object_create_stolen_for_preallocated() which assumes
the stuff is inside stolen.
> > The fact that we fail to confirm any of that on integrated
> > parts has always bugged me, but not enough to actually do
> > anything about it. Such a check would be somewhat more involved
> > since we'd have to look at the PTEs. But on discrete sounds like
> > we can get away with a trivial check.
>
> Which PTEs?
The PTEs the plane is actually using. We have no idea where they
actually point to and just assume they represent a 1:1 mapping of
stolen.
I suppose with lmem we'll just start assuming a 1:1 mapping of
the whole lmem rather than just stolen.
--
Ville Syrjälä
Intel
