[PATCH 3/5] drm/i915/gt: Ignore stale context state upon resume

[Chris Wilson]

We leave the kernel_context on the HW as we suspend (and while idle).
There is no guarantee that is complete in memory, so we try to inhibit
restoration from the kernel_context. Reinforce the inhibition by
scrubbing the context.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Reviewed-by: Matthew Auld <matthew.auld at intel.com>
---
 drivers/gpu/drm/i915/gt/intel_lrc.c             | 11 ++++++++++-
 drivers/gpu/drm/i915/gt/intel_ring_submission.c |  2 +-
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c
index 4f91151843d9..031d66ce5bb5 100644
--- a/drivers/gpu/drm/i915/gt/intel_lrc.c
+++ b/drivers/gpu/drm/i915/gt/intel_lrc.c
@@ -2663,6 +2663,9 @@ static int execlists_context_alloc(struct intel_context *ce)
 
 static void execlists_context_reset(struct intel_context *ce)
 {
+	CE_TRACE(ce, "reset\n");
+	GEM_BUG_ON(!intel_context_is_pinned(ce));
+
 	/*
 	 * Because we emit WA_TAIL_DWORDS there may be a disparity
 	 * between our bookkeeping in ce->ring->head and ce->ring->tail and
@@ -2679,8 +2682,14 @@ static void execlists_context_reset(struct intel_context *ce)
 	 * So to avoid that we reset the context images upon resume. For
 	 * simplicity, we just zero everything out.
 	 */
-	intel_ring_reset(ce->ring, 0);
+	intel_ring_reset(ce->ring, ce->ring->emit);
+
+	/* Scrub away the garbage */
+	execlists_init_reg_state(ce->lrc_reg_state,
+				 ce, ce->engine, ce->ring, true);
 	__execlists_update_reg_state(ce, ce->engine);
+
+	ce->lrc_desc |= CTX_DESC_FORCE_RESTORE;
 }
 
 static const struct intel_context_ops execlists_context_ops = {
diff --git a/drivers/gpu/drm/i915/gt/intel_ring_submission.c b/drivers/gpu/drm/i915/gt/intel_ring_submission.c
index 066c4eddf5d0..843111b7b015 100644
--- a/drivers/gpu/drm/i915/gt/intel_ring_submission.c
+++ b/drivers/gpu/drm/i915/gt/intel_ring_submission.c
@@ -1347,7 +1347,7 @@ static int ring_context_pin(struct intel_context *ce)
 
 static void ring_context_reset(struct intel_context *ce)
 {
-	intel_ring_reset(ce->ring, 0);
+	intel_ring_reset(ce->ring, ce->ring->emit);
 }
 
 static const struct intel_context_ops ring_context_ops = {
-- 
2.25.0.rc0