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Peak Tops Limiter (PTL) sysfs Interface

Documentation/gpu/amdgpu/ptl.rst

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======================================= 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

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.