drm/amd/display: Use double buffered DRR timing update by default

[Why]
For some monitors extreme flickering can occur while using LFC for if
we're not doing the DRR timing update for V_TOTAL_MIN / V_TOTAL_MAX at
the DP start of frame.

Hardware can default to any time in the frame which isn't the behavior
we want.

[How]
Add a new function for setting the double buffering mode for DRR timing.

Default to DP start of frame double buffering on timing generator init.
Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Reviewed-by: Aric Cyr <Aric.Cyr@amd.com>
Acked-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/dcn10/dcn10_optc.c

@@ -342,6 +342,23 @@ void optc1_set_blank_data_double_buffer(struct timing_generator *optc, bool enab
 			OTG_BLANK_DATA_DOUBLE_BUFFER_EN, blank_data_double_buffer_enable);
 }
 
+/**
+ * optc1_set_timing_double_buffer() - DRR double buffering control
+ *
+ * Sets double buffer point for V_TOTAL, H_TOTAL, VTOTAL_MIN,
+ * VTOTAL_MAX, VTOTAL_MIN_SEL and VTOTAL_MAX_SEL registers.
+ *
+ * Options: any time,  start of frame, dp start of frame (range timing)
+ */
+void optc1_set_timing_double_buffer(struct timing_generator *optc, bool enable)
+{
+	struct optc *optc1 = DCN10TG_FROM_TG(optc);
+	uint32_t mode = enable ? 2 : 0;
+
+	REG_UPDATE(OTG_DOUBLE_BUFFER_CONTROL,
+		   OTG_RANGE_TIMING_DBUF_UPDATE_MODE, mode);
+}
+
 /**
  * unblank_crtc
  * Call ASIC Control Object to UnBlank CRTC.
@@ -1353,6 +1370,7 @@ void optc1_clear_optc_underflow(struct timing_generator *optc)
 void optc1_tg_init(struct timing_generator *optc)
 {
 	optc1_set_blank_data_double_buffer(optc, true);
+	optc1_set_timing_double_buffer(optc, true);
 	optc1_clear_optc_underflow(optc);
 }
 

drivers/gpu/drm/amd/display/dc/dcn10/dcn10_optc.h

@@ -185,6 +185,7 @@ struct dcn_optc_registers {
 	SF(OTG0_OTG_GLOBAL_CONTROL0, OTG_MASTER_UPDATE_LOCK_SEL, mask_sh),\
 	SF(OTG0_OTG_DOUBLE_BUFFER_CONTROL, OTG_UPDATE_PENDING, mask_sh),\
 	SF(OTG0_OTG_DOUBLE_BUFFER_CONTROL, OTG_BLANK_DATA_DOUBLE_BUFFER_EN, mask_sh),\
+	SF(OTG0_OTG_DOUBLE_BUFFER_CONTROL, OTG_RANGE_TIMING_DBUF_UPDATE_MODE, mask_sh),\
 	SF(OTG0_OTG_H_TOTAL, OTG_H_TOTAL, mask_sh),\
 	SF(OTG0_OTG_H_BLANK_START_END, OTG_H_BLANK_START, mask_sh),\
 	SF(OTG0_OTG_H_BLANK_START_END, OTG_H_BLANK_END, mask_sh),\
@@ -643,6 +644,8 @@ bool optc1_is_optc_underflow_occurred(struct timing_generator *optc);
 
 void optc1_set_blank_data_double_buffer(struct timing_generator *optc, bool enable);
 
+void optc1_set_timing_double_buffer(struct timing_generator *optc, bool enable);
+
 bool optc1_get_otg_active_size(struct timing_generator *optc,
 		uint32_t *otg_active_width,
 		uint32_t *otg_active_height);