drm/amd/display: Enforce 60us prefetch for 200Mhz DCFCLK modes

commit b504f99 upstream.

[Description]
- Due to bandwidth / arbitration issues at 200Mhz DCFCLK,
  we want to enforce minimum 60us of prefetch to avoid
  intermittent underflow issues
- Since 60us prefetch is already enforced for UCLK DPM0,
  and many DCFCLK's > 200Mhz are mapped to UCLK DPM1, in
  theory there should not be any UCLK DPM regressions by
  enforcing greater prefetch

Reviewed-by: Nevenko Stupar <Nevenko.Stupar@amd.com>
Reviewed-by: Jun Lei <Jun.Lei@amd.com>
Cc: Mario Limonciello <mario.limonciello@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org
Acked-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Alvin Lee <Alvin.Lee2@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/gpu/drm/amd/display/dc/dml/dcn32/display_mode_vba_32.c

@@ -807,7 +807,8 @@ static void DISPCLKDPPCLKDCFCLKDeepSleepPrefetchParametersWatermarksAndPerforman
 					v->SwathHeightY[k],
 					v->SwathHeightC[k],
 					TWait,
-					v->DRAMSpeedPerState[mode_lib->vba.VoltageLevel] <= MEM_STROBE_FREQ_MHZ ?
+					(v->DRAMSpeedPerState[mode_lib->vba.VoltageLevel] <= MEM_STROBE_FREQ_MHZ ||
+						v->DCFCLKPerState[mode_lib->vba.VoltageLevel] <= MIN_DCFCLK_FREQ_MHZ) ?
 							mode_lib->vba.ip.min_prefetch_in_strobe_us : 0,
 					/* Output */
 					&v->DSTXAfterScaler[k],
@@ -3288,7 +3289,7 @@ void dml32_ModeSupportAndSystemConfigurationFull(struct display_mode_lib *mode_l
 							v->swath_width_chroma_ub_this_state[k],
 							v->SwathHeightYThisState[k],
 							v->SwathHeightCThisState[k], v->TWait,
-							v->DRAMSpeedPerState[i] <= MEM_STROBE_FREQ_MHZ ?
+							(v->DRAMSpeedPerState[i] <= MEM_STROBE_FREQ_MHZ || v->DCFCLKState[i][j] <= MIN_DCFCLK_FREQ_MHZ) ?
 									mode_lib->vba.ip.min_prefetch_in_strobe_us : 0,
 
 							/* Output */

drivers/gpu/drm/amd/display/dc/dml/dcn32/display_mode_vba_32.h

@@ -52,6 +52,7 @@
 #define BPP_BLENDED_PIPE 0xffffffff
 
 #define MEM_STROBE_FREQ_MHZ 1600
+#define MIN_DCFCLK_FREQ_MHZ 200
 #define MEM_STROBE_MAX_DELIVERY_TIME_US 60.0
 
 struct display_mode_lib;