drm/amd/display: Add a sanity check for DSC already enabled/disabled

[why]
If acquire/release DSC resource sequence is affected by a regression,
it can happen that the already-in-use DSC HW block is being wrongly
re-used for a different pipe. The reverse is also possible, i.e.
already-disabled DSC HW block could be disabled from other context.

[how]
Read back the enable state of DSC HW and report an error if duplicate
enable or disable was attempted.
Signed-off-by: Nikola Cornij <nikola.cornij@amd.com>
Reviewed-by: Dmytro Laktyushkin <Dmytro.Laktyushkin@amd.com>
Acked-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/dcn20/dcn20_dsc.c

@@ -222,9 +222,18 @@ static bool dsc2_get_packed_pps(struct display_stream_compressor *dsc, const str
 static void dsc2_enable(struct display_stream_compressor *dsc, int opp_pipe)
 {
 	struct dcn20_dsc *dsc20 = TO_DCN20_DSC(dsc);
+	int dsc_clock_en;
+	int dsc_fw_config;
+	int enabled_opp_pipe;
 
-	/* TODO Check if DSC alreay in use? */
-	DC_LOG_DSC("enable DSC at opp pipe %d", opp_pipe);
+	DC_LOG_DSC("enable DSC %d at opp pipe %d", dsc->inst, opp_pipe);
+
+	REG_GET(DSC_TOP_CONTROL, DSC_CLOCK_EN, &dsc_clock_en);
+	REG_GET_2(DSCRM_DSC_FORWARD_CONFIG, DSCRM_DSC_FORWARD_EN, &dsc_fw_config, DSCRM_DSC_OPP_PIPE_SOURCE, &enabled_opp_pipe);
+	if ((dsc_clock_en || dsc_fw_config) && enabled_opp_pipe != opp_pipe) {
+		DC_LOG_DSC("ERROR: DSC %d at opp pipe %d already enabled!", dsc->inst, enabled_opp_pipe);
+		ASSERT(0);
+	}
 
 	REG_UPDATE(DSC_TOP_CONTROL,
 		DSC_CLOCK_EN, 1);
@@ -238,8 +247,18 @@ static void dsc2_enable(struct display_stream_compressor *dsc, int opp_pipe)
 static void dsc2_disable(struct display_stream_compressor *dsc)
 {
 	struct dcn20_dsc *dsc20 = TO_DCN20_DSC(dsc);
+	int dsc_clock_en;
+	int dsc_fw_config;
+	int enabled_opp_pipe;
 
-	DC_LOG_DSC("disable DSC");
+	DC_LOG_DSC("disable DSC %d", dsc->inst);
+
+	REG_GET(DSC_TOP_CONTROL, DSC_CLOCK_EN, &dsc_clock_en);
+	REG_GET_2(DSCRM_DSC_FORWARD_CONFIG, DSCRM_DSC_FORWARD_EN, &dsc_fw_config, DSCRM_DSC_OPP_PIPE_SOURCE, &enabled_opp_pipe);
+	if (!dsc_clock_en || !dsc_fw_config) {
+		DC_LOG_DSC("ERROR: DSC %d at opp pipe %d already disabled!", dsc->inst, enabled_opp_pipe);
+		ASSERT(0);
+	}
 
 	REG_UPDATE(DSCRM_DSC_FORWARD_CONFIG,
 		DSCRM_DSC_FORWARD_EN, 0);