The AMD Open Source Driver for Vulkan® is an open-source Vulkan driver for Radeon™ graphics adapters on Linux®. It is built on top of AMD's Platform Abstraction Library (PAL), a shared component that is designed to encapsulate certain hardware and OS-specific programming details for many of AMD's 3D and compute drivers. Leveraging PAL can help provide a consistent experience across platforms, including support for recently released GPUs and compatibility with AMD developer tools.
Shaders that compose a particular `VkPipeline` object are compiled as a single entity using the LLVM-Based Pipeline Compiler (LLPC) library. LLPC builds on LLVM's existing shader compilation infrastructure for AMD GPUs to generate code objects compatible with PAL's pipeline ABI. Notably, AMD's closed-source Vulkan driver currently uses a different pipeline compiler, which is the major difference between AMD's open-source and closed-source Vulkan drivers.
The AMD Open Source Driver for Vulkan is designed to support following distros on both the AMDGPU upstream driver stack and the [AMDGPU Pro driver stack](https://support.amd.com/en-us/kb-articles/Pages/Radeon-Software-for-Linux-Release-Notes.aspx):
> **Note:** To run the Vulkan driver with AMDGPU upstream driver stack on SI and CI generation GPUs, amdgpu.si_support and amdgpu.cik_support need to be enabled in kernel
The following features and improvements are planned in future releases (Please refer to [Release Notes](https://github.com/GPUOpen-Drivers/AMDVLK/wiki/Release-notes) for update of each release):
* The driver can only work with firmware of ME feature version >= 25 (you can check the version with command "sudo cat /sys/kernel/debug/dri/0/amdgpu_firmware_info"). If you are using upstream stack with GPUs of SI or CI family, you may need to upgrade the kernel to 4.19 or later version and firmware (under /lib/firmware/amdgpu/) to the right version from https://git.kernel.org/pub/scm/linux/kernel/git/firmware/linux-firmware.git/tree/amdgpu, and then update ramfs (sudo mkinitramfs -o /boot/initrd.img-\`uname -r\` \`uname -r\`)
* Timeline semaphore is not fully supported in Linux kernel until version 5.5. You can install [Vulkan timeline semaphore layer](https://github.com/KhronosGroup/Vulkan-ExtensionLayer) to enable the extension if you are using earlier version of Linux kernel
The driver is built from source code in four repositories: [LLVM](https://github.com/GPUOpen-Drivers/llvm-project), [XGL](https://github.com/GPUOpen-Drivers/xgl), [LLPC](https://github.com/GPUOpen-Drivers/llpc) and [PAL](https://github.com/GPUOpen-Drivers/pal).
For changes to LLVM, you should submit contribution to the [LLVM trunk](https://reviews.llvm.org/). Commits there will be evaluated to merge into the amd-gfx-gpuopen-master branch periodically.
For changes to XGL, LLPC and PAL, please [create a pull request](https://help.github.com/articles/creating-a-pull-request/) against the dev branch. After your change is reviewed and if it is accepted, it will be evaluated to merge into the master branch in a subsequent regular promotion.
**IMPORTANT**: By creating a pull request, you agree to allow your contribution to be licensed by the project owners under the terms of the [MIT License](LICENSE.txt).
* Match the style of nearby existing code. Your code may be edited to comply with our coding standards when it is merged into the master branch.
* Avoid adding new dependencies, including dependencies on STL.
Please make each contribution reasonably small. If you would like to make a big contribution, like a new feature or extension, please raise an issue first to allow planning to evaluate and review your work.
> **Note:** Since PAL is a shared component that must support other APIs, other operating systems, and pre-production hardware, you might be asked to revise your PAL change for reasons that may not be obvious from a pure Linux Vulkan driver perspective.
* For debug build, use `-DCMAKE_BUILD_TYPE=Debug -DLLVM_PARALLEL_LINK_JOBS=2` (Linking a debug build of llvm is very memory intensive, so we use only two parallel jobs).
> If RADV is also installed in the system, AMDVLK driver will be enabled by default after installation. You can switch the driver between AMDVLK and RADV by environment variable AMD_VULKAN_ICD = AMDVLK or RADV.
On the AMDGPU upstream driver stack with libdrm version lower than 2.4.92, the max number of IB per submission **MUST** be limited to 4 (the default setting in AMD Open Source driver for Vulkan is 16). This can be accomplished via the [Runtime Settings](#runtime-settings) mechanism by adding the following line to amdPalSettings.cfg:
The driver exposes many settings that can customize the driver's behavior and facilitate debugging. You can add/edit settings in amdPalSettings.cfg file under one of below paths, formatted with one `name,value` pair per line:
| `AllowVkPipelineCachingToDisk` | 0: disallow<br/>1: default<br/> | 1 is default value which enables Pal's archive-file based caching.<br/>The archive-file is stored under ~/.cache/AMD/VkCache. |
| `ShaderCacheMode` | 0: disable cache<br/>1: runtime cache<br/>2: cache to disk | Runtime cache is the default mode. For "cache to disk", the cache file is generated under $AMD_SHADER_DISK_CACHE_PATH/AMD/LlpcCache or $XDG_CACHE_HOME/AMD/LlpcCache or $HOME/.cache/AMD/LlpcCache |
| `IFH` | 0: default<br/>1: drop all submits<br/> | Infinitely Fast Hardware. Submit calls are dropped before being sent to hardware. Useful for measuring CPU-limited performance. |
| `EnableVmAlwaysValid` | 0: disable<br/>1: default<br/>2: force enable<br/> | 1 is the default setting which enables the VM-always-valid feature for kernel 4.16 and above. The feature can reduce command buffer submission overhead related to virtual memory management. |
| `IdleAfterSubmitGpuMask` | Bitmask of GPUs (i.e., bit 0 is GPU0, etc.) | Forces the CPU to immediately wait for each GPU submission to complete on the specified set of GPUs. |
Runtime settings are only read at device initialization, and cannot be changed without restarting the application. If running on a system with multiple GPUs, the same settings will apply to all of them. Lines in the settings file that start with `;` will be treated as comments.
The GpuProfiler is an optional layer that is designed to intercept the PAL interface to provide basic GPU profiling support. Currently, this layer is controlled exclusively through runtime settings and outputs its results to file.
You can use the following [Runtime Settings](#runtime-settings) to generate .csv files with GPU timings of work performed during the designated frames of an application (one file for each frame):
| `GpuProfilerMode` | 0: disable<br/>1: enable with sqtt off<br/>2: enable with sqtt for thread trace<br/>3: enable with sqtt for RGP | Enables and sets the SQTT mode for the GPU performance profiler layer. Actual capture of performance data must be specified via frame number with GpuProfilerConfig_StartFrame or by pressing shift-F11. |
| `GpuProfilerConfig.LogDirectory` | <nobr><directory-path></nobr> | The directory path is relative to $AMD_DEBUG_DIR or $TMPDIR or /var/tmp/, default value is "amdpal/". Your application must have write permissions to the directory. The profiling logs are output to a subdirectory that is named in the format like <nobr><AppName></nobr>_<nobr><yyyy-MM-dd></nobr>_<nobr><HH:mm:ss></nobr>. |
| `GpuProfilerConfig.Granularity` | 0: per-draw<br/>1: per-cmdbuf | Defines what is measured/profiled. *Per-draw* times individual commands (such as draw, dispatch, etc.) inside command buffers, while *per-cmdbuf* only profiles entire command buffers in aggregate. |
| `GpuProfilerConfig.StartFrame` | Positive integer | First frame to capture data for. If StartFrame and FrameCount are not set, all frames will be profiled. |
| `GpuProfilerConfig.FrameCount` | Positive integer | Number of frames to capture data for. |
| `GpuProfilerConfig.RecordPipelineStats` | 0, 1 | Gathers pipeline statistic query data per entry if enabled. |
You can use the script [timingReport.py](https://github.com/GPUOpen-Drivers/pal/tree/master/tools/gpuProfilerTools/timingReport.py) to analyze the profiling log:
PipelineDumpDir is a sub-path relative to $AMD_DEBUG_DIR or $TMPDIR or /var/tmp/, default value is "spvPipeline/". The pipeline dump file is named in the format like Pipeline<nobr><Type></nobr>_<nobr><Compiler_Hash></nobr>.pipe. For example, the above top 1 pipeline is dumped to PipelineVsFs_0xD91D15E42D62DCBB.pipe. The shaders referenced by each pipeline are also dumped to .spv files.
PAL's debug overlay can be enabled to display real time statistics and information on top of a running application. This includes a rolling FPS average, CPU and GPU frame times, and a ledger tracking how much video memory has been allocated from each available heap. Benchmarking (i.e., "Benchmark (F11)") is currently unsupported.
| `DebugOverlayConfig.DebugOverlayLocation` | <nobr>0: top-left</nobr><br/><nobr>1: top-right</nobr><br/><nobr>2: bottom-left</nobr><br/><nobr>3: bottom-right</nobr> | Determines where the overlay text should be displayed. Can be used to avoid collision with important rendering by the application. |
| `DebugOverlayConfig.PrintFrameNumber` | 0, 1 | Reports the current frame number. Useful when determining a good frame range for profiling with the GpuProfiler layer. |
| `DebugOverlayConfig.TimeGraphEnable` | 0, 1 | Enables rendering of a graph of recent CPU and GPU frame times. |
* [LLVM](https://github.com/GPUOpen-Drivers/llvm-project) is distributed under the Apache License v2.0 with LLVM Exceptions. See LICENSE.TXT file in the top directory of the LLVM repository.
* [MetroHash](https://github.com/GPUOpen-Drivers/MetroHash) is distributed under the terms of Apache License 2.0. See LICENSE file in the top directory of the MetroHash repository.
* [CWPack](https://github.com/GPUOpen-Drivers/CWPack) is distributed under the terms of MITLicense. See LICENSE file in the top directory of the CWPack repository.
* Please see the README.md file in the [PAL](https://github.com/GPUOpen-Drivers/pal), [LLPC](https://github.com/GPUOpen-Drivers/llpc) and [XGL](https://github.com/GPUOpen-Drivers/xgl) repositories for information on third party software used by those libraries.
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