On Thu, Feb 5, 2026 at 11:57 AM Perry Yuan <[email protected]> wrote: > > The PTL (Peak Tops Limiter) feature exposes per-GPU sysfs files under > /sys/class/drm/cardX/device/ptl/ to allow users to enable or disable PTL, > configure preferred data formats, and query supported formats. The usage > of these sysfs files is not always obvious, so add documentation to > describe their purpose and provide concrete usage examples. > > V3 changes: > * format show will display preferred formats instead of N/A (Alex) > > Signed-off-by: Perry Yuan <[email protected]> > Suggested-by: Alex Deucher <[email protected]> > Reviewed-by: Yifan Zhang <[email protected]> > --- > Documentation/gpu/amdgpu/index.rst | 1 + > Documentation/gpu/amdgpu/ptl.rst | 94 ++++++++++++++++++++++++++++++ > 2 files changed, 95 insertions(+) > create mode 100644 Documentation/gpu/amdgpu/ptl.rst > > diff --git a/Documentation/gpu/amdgpu/index.rst > b/Documentation/gpu/amdgpu/index.rst > index 8732084186a4..b2ab182236ef 100644 > --- a/Documentation/gpu/amdgpu/index.rst > +++ b/Documentation/gpu/amdgpu/index.rst > @@ -23,3 +23,4 @@ Next (GCN), Radeon DNA (RDNA), and Compute DNA (CDNA) > architectures. > debugfs > process-isolation > amdgpu-glossary > + ptl > diff --git a/Documentation/gpu/amdgpu/ptl.rst > b/Documentation/gpu/amdgpu/ptl.rst > new file mode 100644 > index 000000000000..c7f16dea7954 > --- /dev/null > +++ b/Documentation/gpu/amdgpu/ptl.rst > @@ -0,0 +1,94 @@ > +======================================= > +Peak Tops Limiter (PTL) sysfs Interface > +======================================= > + > +Overview > +-------- > +The Peak Tops Limiter (PTL) sysfs interface enables users to control and > +configure the PTL feature for each GPU individually. All PTL-related > +sysfs files are located under `/sys/class/drm/cardX/device/ptl/`, where > +`X` is the GPU index. Through these files, users can enable or disable > +PTL, set preferred data formats, and query supported formats for each GPU. > + > +PTL sysfs files > +---------------- > +The following files are available under `/sys/class/drm/cardX/device/ptl/`: > + > +- `ptl_enable` > +- `ptl_format` > +- `ptl_supported_formats` > + > +PTL Enable/Disable > +------------------ > +File: `ptl_enable` > +Type: Read/Write (rw) > + > +Read: Returns the current PTL status as a string: `enabled` if PTL > +is active, or `disabled` if inactive. > + > +Write: > + > +- Write `1` or `enabled` to enable PTL > +- Write `0` or `disabled` to disable PTL
Ideally `enable` or `disable`, I.e., drop the "d". Alex > + > +Examples:: > + > + # Query PTL status > + cat /sys/class/drm/card1/device/ptl/ptl_enable > + # Output: enabled > + > + # Enable PTL > + sudo bash -c "echo 1 > /sys/class/drm/card1/device/ptl/ptl_enable" > + > + # Disable PTL > + sudo bash -c "echo 0 > /sys/class/drm/card1/device/ptl/ptl_enable" > + > +PTL Format (Preferred Data Formats) > +----------------------------------- > +File: `ptl_format` > +Type: Read/Write (rw) > + > +Read: Returns the two preferred formats, e.g. `I8,F32`. > + > +Write: Accepts two formats separated by a comma, e.g. `I8,F32`. > + > +- Both formats must be supported and different. > +- If an invalid format is provided (not supported, or both formats are the > + same), the driver will return "write error: Invalid argument". > + > +Examples:: > + > + # Query PTL formats > + cat /sys/class/drm/card1/device/ptl/ptl_format > + # Output: I8,F32 > + > + # Set PTL formats > + sudo bash -c "echo I8,F32 > /sys/class/drm/card1/device/ptl/ptl_format" > + > +Supported Formats > +----------------- > +File: `ptl_supported_formats` > +Type: Read-only (r) > + > +Read: Returns a comma-separated list of supported formats, e.g. > +`I8,F16,BF16,F32,F64`. > + > +Example:: > + > + # Check supported formats > + cat /sys/class/drm/card1/device/ptl/ptl_supported_formats > + # Output: I8,F16,BF16,F32,F64 > + > +Behavioral Notes > +---------------- > +- PTL formats can only be set when PTL is enabled. > +- If PTL is disabled, `ptl_format` returns `N/A`. > +- Only two formats can be set at a time, and they must be from the supported > set and different.. > +- All commands support per-GPU targeting. > +- Root permission is required to enable/disable PTL or change formats. > +- If the hardware does not support PTL, the PTL sysfs directory will not > + be created. > + > +Implementation > +-------------- > +The PTL sysfs nodes are implemented in > `drivers/gpu/drm/amd/amdgpu/amdgpu_psp.c`. > -- > 2.34.1 >
