linux.git/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_ism.c, branch master Linux kernel source tree drm/amd/display: Add Idle state manager(ISM) 2026-03-30T19:14:05+00:00 Ray Wu ray.wu@amd.com 2025-12-17T08:36:02+00:00 754003486c3cc95f2fcb9d6b71a779047d6db95c [Why] Rapid allow/disallow of idle optimization calls, whether it be IPS or self-refresh features, can end up using more power if actual time-in-idle is low. It can also spam DMUB command submission in a way that prevents it from servicing other requestors. [How] Introduce the Idle State Manager (ISM) to amdgpu. It maintains a finite state machine that uses a hysteresis to determine if a delay should be inserted between a caller allowing idle, and when the actual idle optimizations are programmed. A second timer is also introduced to enable static screen optimizations (SSO) such as PSR1 and Replay low HZ idle mode. Rapid SSO enable/disable can have a negative power impact on some low hz video playback, and can introduce user lag for PSR1 (due to up to 3 frames of sync latency). This effectively rate-limits idle optimizations, based on hysteresis. This also replaces the existing delay logic used for PSR1, allowing drm_vblank_crtc_config.disable_immediate = true, and thus allowing drm_crtc_vblank_restore(). v2: * Loosen criteria for ISM to exit idle optimizations; it failed to exit idle correctly on cursor updates when there are no drm_vblank requestors, * Document default_ism_config * Convert pr_debug to trace events to reduce overhead on frequent codepaths * checkpatch.pl fixes Link: https://gitlab.freedesktop.org/drm/amd/-/issues/4527 Link: https://gitlab.freedesktop.org/drm/amd/-/issues/3709 Fixes: 58a261bfc967 ("drm/amd/display: use a more lax vblank enable policy for older ASICs") Signed-off-by: Ray Wu <ray.wu@amd.com> Signed-off-by: Leo Li <sunpeng.li@amd.com> Reviewed-by: Mario Limonciello (AMD) <superm1@kernel.org> Signed-off-by: Alex Deucher <alexander.deucher@amd.com> 
[Why]

Rapid allow/disallow of idle optimization calls, whether it be IPS or
self-refresh features, can end up using more power if actual
time-in-idle is low. It can also spam DMUB command submission in a way
that prevents it from servicing other requestors.

[How]

Introduce the Idle State Manager (ISM) to amdgpu. It maintains a finite
state machine that uses a hysteresis to determine if a delay should be
inserted between a caller allowing idle, and when the actual idle
optimizations are programmed.

A second timer is also introduced to enable static screen optimizations
(SSO) such as PSR1 and Replay low HZ idle mode. Rapid SSO enable/disable
can have a negative power impact on some low hz video playback, and can
introduce user lag for PSR1 (due to up to 3 frames of sync latency).

This effectively rate-limits idle optimizations, based on hysteresis.

This also replaces the existing delay logic used for PSR1, allowing
drm_vblank_crtc_config.disable_immediate = true, and thus allowing
drm_crtc_vblank_restore().

v2:
* Loosen criteria for ISM to exit idle optimizations; it failed to exit
  idle correctly on cursor updates when there are no drm_vblank
  requestors,
* Document default_ism_config
* Convert pr_debug to trace events to reduce overhead on frequent
  codepaths
* checkpatch.pl fixes

Link: https://gitlab.freedesktop.org/drm/amd/-/issues/4527
Link: https://gitlab.freedesktop.org/drm/amd/-/issues/3709
Fixes: 58a261bfc967 ("drm/amd/display: use a more lax vblank enable policy for older ASICs")
Signed-off-by: Ray Wu <ray.wu@amd.com>
Signed-off-by: Leo Li <sunpeng.li@amd.com>
Reviewed-by: Mario Limonciello (AMD) <superm1@kernel.org>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>