drm/amdgpu/dce8: optimize pageflip

Taking the grph update lock is only necessary when
updating the the secondary address (for single pipe stereo).

Reviewed-by: Christian König <[e-mail]>
Reviewed-by: Jammy Zhou <[e-mail]>
Signed-off-by: Alex Deucher <[e-mail]>

drivers/gpu/drm/amd/amdgpu/dce_v8_0.c

···
  * @crtc_id: crtc to cleanup pageflip on
  * @crtc_base: new address of the crtc (GPU MC address)
  *
- * Does the actual pageflip (evergreen+).
- * During vblank we take the crtc lock and wait for the update_pending
- * bit to go high, when it does, we release the lock, and allow the
- * double buffered update to take place.
- * Returns the current update pending status.
+ * Triggers the actual pageflip by updating the primary
+ * surface base address.
  */
 static void dce_v8_0_page_flip(struct amdgpu_device *adev,
 			      int crtc_id, u64 crtc_base)
 {
 	struct amdgpu_crtc *amdgpu_crtc = adev->mode_info.crtcs[crtc_id];
-	u32 tmp = RREG32(mmGRPH_UPDATE + amdgpu_crtc->crtc_offset);
-	int i;
 
-	/* Lock the graphics update lock */
-	tmp |= GRPH_UPDATE__GRPH_UPDATE_LOCK_MASK;
-	WREG32(mmGRPH_UPDATE + amdgpu_crtc->crtc_offset, tmp);
-
-	/* update the scanout addresses */
-	WREG32(mmGRPH_SECONDARY_SURFACE_ADDRESS_HIGH + amdgpu_crtc->crtc_offset,
-	       upper_32_bits(crtc_base));
-	WREG32(mmGRPH_SECONDARY_SURFACE_ADDRESS + amdgpu_crtc->crtc_offset,
-	       (u32)crtc_base);
-
+	/* update the primary scanout addresses */
 	WREG32(mmGRPH_PRIMARY_SURFACE_ADDRESS_HIGH + amdgpu_crtc->crtc_offset,
 	       upper_32_bits(crtc_base));
+	/* writing to the low address triggers the update */
 	WREG32(mmGRPH_PRIMARY_SURFACE_ADDRESS + amdgpu_crtc->crtc_offset,
-	       (u32)crtc_base);
-
-	/* Wait for update_pending to go high. */
-	for (i = 0; i < adev->usec_timeout; i++) {
-		if (RREG32(mmGRPH_UPDATE + amdgpu_crtc->crtc_offset) &
-				GRPH_UPDATE__GRPH_SURFACE_UPDATE_PENDING_MASK)
-			break;
-		udelay(1);
-	}
-	DRM_DEBUG("Update pending now high. Unlocking vupdate_lock.\n");
-
-	/* Unlock the lock, so double-buffering can take place inside vblank */
-	tmp &= ~GRPH_UPDATE__GRPH_UPDATE_LOCK_MASK;
-	WREG32(mmGRPH_UPDATE + amdgpu_crtc->crtc_offset, tmp);
+	       lower_32_bits(crtc_base));
+	/* post the write */
+	RREG32(mmGRPH_PRIMARY_SURFACE_ADDRESS + amdgpu_crtc->crtc_offset);
 }
 
 static int dce_v8_0_crtc_get_scanoutpos(struct amdgpu_device *adev, int crtc,