drm/amdgpu: remove unsafe optimization to drop preamble ib

Take the situation with gfxoff, the optimization may cause
corrupt CE ram contents. In addition emit_cntxcntl callback
has similar optimization which firmware can handle properly
even for power feature.
Signed-off-by: Jiansong Chen <Jiansong.Chen@amd.com>
Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu_ib.c

@@ -130,7 +130,7 @@ int amdgpu_ib_schedule(struct amdgpu_ring *ring, unsigned num_ibs,
 	struct amdgpu_device *adev = ring->adev;
 	struct amdgpu_ib *ib = &ibs[0];
 	struct dma_fence *tmp = NULL;
-	bool skip_preamble, need_ctx_switch;
+	bool need_ctx_switch;
 	unsigned patch_offset = ~0;
 	struct amdgpu_vm *vm;
 	uint64_t fence_ctx;
@@ -227,7 +227,6 @@ int amdgpu_ib_schedule(struct amdgpu_ring *ring, unsigned num_ibs,
 	if (need_ctx_switch)
 		status |= AMDGPU_HAVE_CTX_SWITCH;
 
-	skip_preamble = ring->current_ctx == fence_ctx;
 	if (job && ring->funcs->emit_cntxcntl) {
 		status |= job->preamble_status;
 		status |= job->preemption_status;
@@ -245,14 +244,6 @@ int amdgpu_ib_schedule(struct amdgpu_ring *ring, unsigned num_ibs,
 	for (i = 0; i < num_ibs; ++i) {
 		ib = &ibs[i];
 
-		/* drop preamble IBs if we don't have a context switch */
-		if ((ib->flags & AMDGPU_IB_FLAG_PREAMBLE) &&
-		    skip_preamble &&
-		    !(status & AMDGPU_PREAMBLE_IB_PRESENT_FIRST) &&
-		    !amdgpu_mcbp &&
-		    !amdgpu_sriov_vf(adev)) /* for SRIOV preemption, Preamble CE ib must be inserted anyway */
-			continue;
-
 		if (job && ring->funcs->emit_frame_cntl) {
 			if (secure != !!(ib->flags & AMDGPU_IB_FLAGS_SECURE)) {
 				amdgpu_ring_emit_frame_cntl(ring, false, secure);