drm/i915/migrate: fix corner case in CCS aux copying

In the case of lmem -> lmem transfers, which is currently only possible
with small-bar systems, we need to ensure we copy the CCS aux state
as-is, rather than nuke it. This should fix some nasty display
corruption sometimes seen on DG2 small-bar systems, when also using
DG2_RC_CCS_CC for the surface.

Fixes: e3afc690188b ("drm/i915/display: consider DG2_RC_CCS_CC when migrating buffers")
Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Nirmoy Das <nirmoy.das@intel.com>
Cc: Andrzej Hajda <andrzej.hajda@intel.com>
Cc: Shuicheng Lin <shuicheng.lin@intel.com>
Reviewed-by: Nirmoy Das <nirmoy.das@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221212171958.82593-1-matthew.auld@intel.com

diff --git a/drivers/gpu/drm/i915/gt/intel_migrate.c b/drivers/gpu/drm/i915/gt/intel_migrate.c
index e08a739..3f638f1 100644 (file)
--- a/drivers/gpu/drm/i915/gt/intel_migrate.c
+++ b/drivers/gpu/drm/i915/gt/intel_migrate.c
@@ -839,14 +839,35 @@ intel_context_migrate_copy(struct intel_context *ce,
                        if (err)
                                goto out_rq;
 
-                       /*
-                        * While we can't always restore/manage the CCS state,
-                        * we still need to ensure we don't leak the CCS state
-                        * from the previous user, so make sure we overwrite it
-                        * with something.
-                        */
-                       err = emit_copy_ccs(rq, dst_offset, INDIRECT_ACCESS,
-                                           dst_offset, DIRECT_ACCESS, len);
+                       if (src_is_lmem) {
+                               /*
+                                * If the src is already in lmem, then we must
+                                * be doing an lmem -> lmem transfer, and so
+                                * should be safe to directly copy the CCS
+                                * state. In this case we have either
+                                * initialised the CCS aux state when first
+                                * clearing the pages (since it is already
+                                * allocated in lmem), or the user has
+                                * potentially populated it, in which case we
+                                * need to copy the CCS state as-is.
+                                */
+                               err = emit_copy_ccs(rq,
+                                                   dst_offset, INDIRECT_ACCESS,
+                                                   src_offset, INDIRECT_ACCESS,
+                                                   len);
+                       } else {
+                               /*
+                                * While we can't always restore/manage the CCS
+                                * state, we still need to ensure we don't leak
+                                * the CCS state from the previous user, so make
+                                * sure we overwrite it with something.
+                                */
+                               err = emit_copy_ccs(rq,
+                                                   dst_offset, INDIRECT_ACCESS,
+                                                   dst_offset, DIRECT_ACCESS,
+                                                   len);
+                       }
+
                        if (err)
                                goto out_rq;