drm/amd/display: enable idle optimizations for linux (MALL stutter)

[Why]
We can only use this feature when the display is idle. When active vblank
irq count is 0 we know all the displays are idle.

[How]
-Add a active vblank irq counter
-Update the counter when we enable/disable vblank irq
-if vblank irq count is 0 we can consider mall stutter
Signed-off-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Nick Kazlauskas <Nicholas.Kazlauskas@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c

@@ -5413,6 +5413,7 @@ static inline int dm_set_vblank(struct drm_crtc *crtc, bool enable)
 	struct amdgpu_crtc *acrtc = to_amdgpu_crtc(crtc);
 	struct amdgpu_device *adev = drm_to_adev(crtc->dev);
 	struct dm_crtc_state *acrtc_state = to_dm_crtc_state(crtc->state);
+	struct amdgpu_display_manager *dm = &adev->dm;
 	int rc = 0;
 
 	if (enable) {
@@ -5428,7 +5429,25 @@ static inline int dm_set_vblank(struct drm_crtc *crtc, bool enable)
 		return rc;
 
 	irq_source = IRQ_TYPE_VBLANK + acrtc->otg_inst;
-	return dc_interrupt_set(adev->dm.dc, irq_source, enable) ? 0 : -EBUSY;
+
+	if (!dc_interrupt_set(adev->dm.dc, irq_source, enable))
+		return -EBUSY;
+
+	mutex_lock(&dm->dc_lock);
+
+	if (enable)
+		dm->active_vblank_irq_count++;
+	else
+		dm->active_vblank_irq_count--;
+
+	dc_allow_idle_optimizations(
+		adev->dm.dc, dm->active_vblank_irq_count == 0 ? true : false);
+
+	DRM_DEBUG_DRIVER("Allow idle optimizations (MALL): %d\n", dm->active_vblank_irq_count == 0);
+
+	mutex_unlock(&dm->dc_lock);
+
+	return 0;
 }
 
 static int dm_enable_vblank(struct drm_crtc *crtc)

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h

@@ -336,6 +336,13 @@ struct amdgpu_display_manager {
 	 */
 	const struct gpu_info_soc_bounding_box_v1_0 *soc_bounding_box;
 
+	/**
+	 * @active_vblank_irq_count
+	 *
+	 * number of currently active vblank irqs
+	 */
+	uint32_t active_vblank_irq_count;
+
 #ifdef CONFIG_DEBUG_FS
 	/**
 	 * @crc_win_x_start_property: