drm/amd/display: Fix FBC text console corruption

Signed-off-by: Roman Li <roman.li@amd.com>
Reviewed-by: Charlene Liu <Charlene.Liu@amd.com>
Acked-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/dce110/dce110_compressor.c

@@ -102,6 +102,43 @@ static uint32_t align_to_chunks_number_per_line(uint32_t pixels)
 	return 256 * ((pixels + 255) / 256);
 }
 
+static void reset_lb_on_vblank(struct dc_context *ctx)
+{
+	uint32_t value, frame_count;
+	uint32_t retry = 0;
+	uint32_t status_pos =
+			dm_read_reg(ctx, mmCRTC_STATUS_POSITION);
+
+
+	/* Only if CRTC is enabled and counter is moving we wait for one frame. */
+	if (status_pos != dm_read_reg(ctx, mmCRTC_STATUS_POSITION)) {
+		/* Resetting LB on VBlank */
+		value = dm_read_reg(ctx, mmLB_SYNC_RESET_SEL);
+		set_reg_field_value(value, 3, LB_SYNC_RESET_SEL, LB_SYNC_RESET_SEL);
+		set_reg_field_value(value, 1, LB_SYNC_RESET_SEL, LB_SYNC_RESET_SEL2);
+		dm_write_reg(ctx, mmLB_SYNC_RESET_SEL, value);
+
+		frame_count = dm_read_reg(ctx, mmCRTC_STATUS_FRAME_COUNT);
+
+
+		for (retry = 100; retry > 0; retry--) {
+			if (frame_count != dm_read_reg(ctx, mmCRTC_STATUS_FRAME_COUNT))
+				break;
+			msleep(1);
+		}
+		if (!retry)
+			dm_error("Frame count did not increase for 100ms.\n");
+
+		/* Resetting LB on VBlank */
+		value = dm_read_reg(ctx, mmLB_SYNC_RESET_SEL);
+		set_reg_field_value(value, 2, LB_SYNC_RESET_SEL, LB_SYNC_RESET_SEL);
+		set_reg_field_value(value, 0, LB_SYNC_RESET_SEL, LB_SYNC_RESET_SEL2);
+		dm_write_reg(ctx, mmLB_SYNC_RESET_SEL, value);
+
+	}
+
+}
+
 static void wait_for_fbc_state_changed(
 	struct dce110_compressor *cp110,
 	bool enabled)
@@ -232,8 +269,8 @@ void dce110_compressor_disable_fbc(struct compressor *compressor)
 {
 	struct dce110_compressor *cp110 = TO_DCE110_COMPRESSOR(compressor);
 
-	if (compressor->options.bits.FBC_SUPPORT &&
-		dce110_compressor_is_fbc_enabled_in_hw(compressor, NULL)) {
+	if (compressor->options.bits.FBC_SUPPORT) {
+		if (dce110_compressor_is_fbc_enabled_in_hw(compressor, NULL)) {
 			uint32_t reg_data;
 			/* Turn off compression */
 			reg_data = dm_read_reg(compressor->ctx, mmFBC_CNTL);
@@ -246,6 +283,10 @@ void dce110_compressor_disable_fbc(struct compressor *compressor)
 
 			wait_for_fbc_state_changed(cp110, false);
 		}
+
+		/* Sync line buffer  - dce100/110 only*/
+		reset_lb_on_vblank(compressor->ctx);
+	}
 }
 
 bool dce110_compressor_is_fbc_enabled_in_hw(