drm/i915/gen8: Dynamic page table allocations

drm/i915/gen8: Dynamic page table allocations

This finishes off the dynamic page tables allocations, in the legacy 3
level style that already exists. Most everything has already been setup
to this point, the patch finishes off the enabling by setting the
appropriate function pointers.

In LRC mode, contexts need to know the PDPs when they are populated. With
dynamic page table allocations, these PDPs may not exist yet. Check if
PDPs have been allocated and use the scratch page if they do not exist yet.

Before submission, update the PDPs in the logic ring context as PDPs
have been allocated.

v2: Update aliasing/true ppgtt allocate/teardown/clear functions for
gen 6 & 7.

v3: Rebase.

v4: Remove BUG() from ppgtt_unbind_vma, but keep checking that either
teardown_va_range or clear_range functions exist (Daniel).

v5: Similar to gen6, in init, gen8_ppgtt_clear_range call is only needed
for aliasing ppgtt. Zombie tracking was originally added for teardown
function and is no longer required.

v6: Update err_out case in gen8_alloc_va_range (missed from lastest
rebase).

v7: Rebase after s/page_tables/page_table/.

v8: Updated scratch_pt check after scratch flag was removed in previous
patch.

v9: Note that lrc mode needs to be updated to support init state without
any PDP.

v10: Unmap correct page_table in gen8_alloc_va_range's error case,  clean-up
gen8_aliasing_ppgtt_init (remove duplicated map), and initialize PTs
during page table allocation.

v11: Squashed LRC enabling commit, otherwise LRC mode would be left broken
until it was updated to handle the init case without any PDP.

v12: Do not overallocate new_pts bitmap, make alloc_gen8_temp_bitmaps
static and don't abuse of inline functions. (Mika)

Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Signed-off-by: Michel Thierry <michel.thierry@intel.com> (v2+)
Reviewed-by: Mika Kuoppala <mika.kuoppala@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>