[PATCH 5/8] drm/amd/display: Enforce 60us prefetch for 200Mhz DCFCLK modes

[Alex Hung]

From: Alvin Lee <Alvin.Lee2 at amd.com>

[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 at amd.com>
Reviewed-by: Jun Lei <Jun.Lei at amd.com>
Cc: Mario Limonciello <mario.limonciello at amd.com>
Cc: Alex Deucher <alexander.deucher at amd.com>
Cc: stable at vger.kernel.org
Acked-by: Alex Hung <alex.hung at amd.com>
Signed-off-by: Alvin Lee <Alvin.Lee2 at amd.com>
---
 .../gpu/drm/amd/display/dc/dml/dcn32/display_mode_vba_32.c   | 5 +++--
 .../gpu/drm/amd/display/dc/dml/dcn32/display_mode_vba_32.h   | 1 +
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/dc/dml/dcn32/display_mode_vba_32.c b/drivers/gpu/drm/amd/display/dc/dml/dcn32/display_mode_vba_32.c
index 66f44a013fe5..958d27224f64 100644
--- a/drivers/gpu/drm/amd/display/dc/dml/dcn32/display_mode_vba_32.c
+++ b/drivers/gpu/drm/amd/display/dc/dml/dcn32/display_mode_vba_32.c
@@ -810,7 +810,8 @@ 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],
@@ -3314,7 +3315,7 @@ 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 */
diff --git a/drivers/gpu/drm/amd/display/dc/dml/dcn32/display_mode_vba_32.h b/drivers/gpu/drm/amd/display/dc/dml/dcn32/display_mode_vba_32.h
index 500b3dd6052d..d98e36a9a09c 100644
--- a/drivers/gpu/drm/amd/display/dc/dml/dcn32/display_mode_vba_32.h
+++ b/drivers/gpu/drm/amd/display/dc/dml/dcn32/display_mode_vba_32.h
@@ -53,6 +53,7 @@
 #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;
-- 
2.40.0