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drm/amd/pm: Treat zero vblank time as too short in si_dpm (v3)

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Some parts of the code base expect that MCLK switching is turned
off when the vblank time is set to zero.

According to pp_pm_compute_clocks the non-DC code has issues
with MCLK switching with refresh rates over 120 Hz.

v3:
Add code comment to explain this better.
Add an if statement instead of changing the switch_limit.

Fixes: 841686df9f ("drm/amdgpu: add SI DPM support (v4)")
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Timur Kristóf <timur.kristof@gmail.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
This commit is contained in:
Timur Kristóf 2025-08-28 17:11:08 +02:00 committed by Alex Deucher
parent ce02513012
commit 9003a07468
1 changed files with 7 additions and 1 deletions
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8
drivers/gpu/drm/amd/pm/legacy-dpm/si_dpm.c
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@ -3085,7 +3085,13 @@ static bool si_dpm_vblank_too_short(void *handle)
/* we never hit the non-gddr5 limit so disable it */ /* we never hit the non-gddr5 limit so disable it */
u32 switch_limit = adev->gmc.vram_type == AMDGPU_VRAM_TYPE_GDDR5 ? 450 : 0; u32 switch_limit = adev->gmc.vram_type == AMDGPU_VRAM_TYPE_GDDR5 ? 450 : 0;
if (vblank_time < switch_limit) /* Consider zero vblank time too short and disable MCLK switching.
* Note that the vblank time is set to maximum when no displays are attached,
* so we'll still enable MCLK switching in that case.
*/
if (vblank_time == 0)
return true;
else if (vblank_time < switch_limit)
return true; return true;
else else
return false; return false;