From 106b4a2a78b2a2f14885604891957b84bba502db Mon Sep 17 00:00:00 2001 From: Adrian Betschart Date: Fri, 11 Sep 2026 17:13:14 +0200 Subject: drm/amd/display: Try RGB before YCbCr 4:4:4 in stream validation amdgpu_dm_create_validate_stream_for_sink() walks encoding_order[] and uses the first encoding that validates. YCbCr 4:4:4 is listed before RGB, so an HDMI sink that advertises 4:4:4 gets YCbCr 4:4:4 whenever the "color format" property is left at AUTO, even though RGB fits the same link. That contradicts the documented AUTO behaviour for HDMI in enum drm_connector_color_format (RGB, falling back to YCbCr 4:2:0 only when the bandwidth is not available or the mode is 4:2:0-only), which the amdgpu implementation of the property also describes. It also leaves the "Broadcast RGB" property without effect on such sinks, since the quantization range it selects only applies to RGB output. Try RGB first. The mask still holds every encoding the sink supports, so a mode that cannot carry RGB falls back exactly as before. For reference, v7.2 picked RGB here unless YCbCr 4:4:4 was forced through debugfs, while earlier kernels picked YCbCr 4:4:4 for any HDMI sink that advertised it. Fixes: 0b0ff65d3ca1 ("drm/amd/display: Refactor stream validation") Suggested-by: Adolfo Rodrigues Assisted-by: Claude Code:claude-fable-5-1 Signed-off-by: Adrian Betschart Reviewed-by: Fangzhi Zuo Tested-by: Adolfo Rodrigues Tested-by: Daniel Wheeler Signed-off-by: Alex Deucher (cherry picked from commit 7de432bc753133764dc40d37f9388da56de251e7) --- Documentation/gpu/amdgpu/ptl.rst | 94 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 94 insertions(+) create mode 100644 Documentation/gpu/amdgpu/ptl.rst (limited to 'Documentation/gpu/amdgpu/ptl.rst') diff --git a/Documentation/gpu/amdgpu/ptl.rst b/Documentation/gpu/amdgpu/ptl.rst new file mode 100644 index 000000000..c7f16dea7 --- /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 + +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`. -- cgit v1.3.1