From 7a06e125872929247f78f363d1dc2dbd528631ab Mon Sep 17 00:00:00 2001 From: André Almeida Date: Thu, 14 Jul 2022 16:17:45 -0300 Subject: Documentation/gpu: Add GFXOFF section MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Add a GFXOFF section at "GPU Power Controls" file, explaining what it is and how userspace can interact with it. v2: minor tweaks to the documenation (Alex) Signed-off-by: André Almeida Signed-off-by: Alex Deucher --- Documentation/gpu/amdgpu/thermal.rst | 41 ++++++++++++++++++++++++++++++++++++ 1 file changed, 41 insertions(+) (limited to 'Documentation/gpu') diff --git a/Documentation/gpu/amdgpu/thermal.rst b/Documentation/gpu/amdgpu/thermal.rst index 8aeb0186c9ef..997231b6adcf 100644 --- a/Documentation/gpu/amdgpu/thermal.rst +++ b/Documentation/gpu/amdgpu/thermal.rst @@ -63,3 +63,44 @@ gpu_metrics .. kernel-doc:: drivers/gpu/drm/amd/pm/amdgpu_pm.c :doc: gpu_metrics + +GFXOFF +====== + +GFXOFF is a feature found in most recent GPUs that saves power at runtime. The +card's RLC (RunList Controller) firmware powers off the gfx engine +dynamically when there is no workload on gfx or compute pipes. GFXOFF is on by +default on supported GPUs. + +Userspace can interact with GFXOFF through a debugfs interface: + +``amdgpu_gfxoff`` +----------------- + +Use it to enable/disable GFXOFF, and to check if it's current enabled/disabled:: + + $ xxd -l1 -p /sys/kernel/debug/dri/0/amdgpu_gfxoff + 01 + +- Write 0 to disable it, and 1 to enable it. +- Read 0 means it's disabled, 1 it's enabled. + +If it's enabled, that means that the GPU is free to enter into GFXOFF mode as +needed. Disabled means that it will never enter GFXOFF mode. + +``amdgpu_gfxoff_status`` +------------------------ + +Read it to check current GFXOFF's status of a GPU:: + + $ xxd -l1 -p /sys/kernel/debug/dri/0/amdgpu_gfxoff_status + 02 + +- 0: GPU is in GFXOFF state, the gfx engine is powered down. +- 1: Transition out of GFXOFF state +- 2: Not in GFXOFF state +- 3: Transition into GFXOFF state + +If GFXOFF is enabled, the value will be transitioning around [0, 3], always +getting into 0 when possible. When it's disabled, it's always at 2. Returns +``-EINVAL`` if it's not supported. -- cgit v1.2.3