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drm/amd/display: For prefetch mode > 0, extend prefetch if possible

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[ Upstream commit dd4e4bb28843393065eed279e869fac248d03f0f ]

[Description]
For mode programming we want to extend the prefetch as much as possible
(up to oto, or as long as we can for equ) if we're not already applying
the 60us prefetch requirement. This is to avoid intermittent underflow
issues during prefetch.

The prefetch extension is applied under the following scenarios:
1. We're in prefetch mode 1 (i.e. we don't support MCLK switch in blank)
2. We're using subvp or drr methods of p-state switch, in which case we
   we don't care if prefetch takes up more of the blanking time

Mode programming typically chooses the smallest prefetch time possible
(i.e. highest bandwidth during prefetch) presumably to create margin between
p-states / c-states that happen in vblank and prefetch. Therefore we only
apply this prefetch extension when p-state in vblank is not required (UCLK
p-states take up the most vblank time).

Reviewed-by: Jun Lei <jun.lei@amd.com>
Acked-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Signed-off-by: Alvin Lee <alvin.lee2@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Alvin Lee 2023-12-06 14:52:31 -05:00 committed by Greg Kroah-Hartman
parent 4ef53b7e30
commit fb017c3e6a
3 changed files with 31 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
drivers/gpu/drm/amd/display/dc/dml/dcn32/display_mode_vba_32.c
View File

@ -810,6 +810,8 @@ static void DISPCLKDPPCLKDCFCLKDeepSleepPrefetchParametersWatermarksAndPerforman
(v->DRAMSpeedPerState[mode_lib->vba.VoltageLevel] <= MEM_STROBE_FREQ_MHZ ||
v->DCFCLKPerState[mode_lib->vba.VoltageLevel] <= DCFCLK_FREQ_EXTRA_PREFETCH_REQ_MHZ) ?
mode_lib->vba.ip.min_prefetch_in_strobe_us : 0,
mode_lib->vba.PrefetchModePerState[mode_lib->vba.VoltageLevel][mode_lib->vba.maxMpcComb] > 0 || mode_lib->vba.DRAMClockChangeRequirementFinal == false,
/* Output */
&v->DSTXAfterScaler[k],
&v->DSTYAfterScaler[k],
@ -3291,6 +3293,7 @@ void dml32_ModeSupportAndSystemConfigurationFull(struct display_mode_lib *mode_l
v->SwathHeightCThisState[k], v->TWait,
(v->DRAMSpeedPerState[i] <= MEM_STROBE_FREQ_MHZ || v->DCFCLKState[i][j] <= DCFCLK_FREQ_EXTRA_PREFETCH_REQ_MHZ) ?
mode_lib->vba.ip.min_prefetch_in_strobe_us : 0,
mode_lib->vba.PrefetchModePerState[i][j] > 0 || mode_lib->vba.DRAMClockChangeRequirementFinal == false,
/* Output */
&v->dummy_vars.dml32_ModeSupportAndSystemConfigurationFull.DSTXAfterScaler[k],

33
drivers/gpu/drm/amd/display/dc/dml/dcn32/display_mode_vba_util_32.c
View File

@ -3418,6 +3418,7 @@ bool dml32_CalculatePrefetchSchedule(
unsigned int SwathHeightC,
double TWait,
double TPreReq,
bool ExtendPrefetchIfPossible,
/* Output */
double *DSTXAfterScaler,
double *DSTYAfterScaler,
@ -3887,12 +3888,32 @@ bool dml32_CalculatePrefetchSchedule(
/* Clamp to oto for bandwidth calculation */
LinesForPrefetchBandwidth = dst_y_prefetch_oto;
} else {
*DestinationLinesForPrefetch = dst_y_prefetch_equ;
TimeForFetchingMetaPTE = Tvm_equ;
TimeForFetchingRowInVBlank = Tr0_equ;
*PrefetchBandwidth = prefetch_bw_equ;
/* Clamp to equ for bandwidth calculation */
LinesForPrefetchBandwidth = dst_y_prefetch_equ;
/* For mode programming we want to extend the prefetch as much as possible
* (up to oto, or as long as we can for equ) if we're not already applying
* the 60us prefetch requirement. This is to avoid intermittent underflow
* issues during prefetch.
*
* The prefetch extension is applied under the following scenarios:
* 1. We're in prefetch mode > 0 (i.e. we don't support MCLK switch in blank)
* 2. We're using subvp or drr methods of p-state switch, in which case we
* we don't care if prefetch takes up more of the blanking time
*
* Mode programming typically chooses the smallest prefetch time possible
* (i.e. highest bandwidth during prefetch) presumably to create margin between
* p-states / c-states that happen in vblank and prefetch. Therefore we only
* apply this prefetch extension when p-state in vblank is not required (UCLK
* p-states take up the most vblank time).
*/
if (ExtendPrefetchIfPossible && TPreReq == 0 && VStartup < MaxVStartup) {
MyError = true;
} else {
*DestinationLinesForPrefetch = dst_y_prefetch_equ;
TimeForFetchingMetaPTE = Tvm_equ;
TimeForFetchingRowInVBlank = Tr0_equ;
*PrefetchBandwidth = prefetch_bw_equ;
/* Clamp to equ for bandwidth calculation */
LinesForPrefetchBandwidth = dst_y_prefetch_equ;
}
}
*DestinationLinesToRequestVMInVBlank = dml_ceil(4.0 * TimeForFetchingMetaPTE / LineTime, 1.0) / 4.0;

1
drivers/gpu/drm/amd/display/dc/dml/dcn32/display_mode_vba_util_32.h
View File

@ -744,6 +744,7 @@ bool dml32_CalculatePrefetchSchedule(
unsigned int SwathHeightC,
double TWait,
double TPreReq,
bool ExtendPrefetchIfPossible,
/* Output */
double *DSTXAfterScaler,
double *DSTYAfterScaler,