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GFX6-8 are the oldest GPUs supported by the amdgpu kernel driver, and the last ones that didn't support DRM format modifiers until now. These are the Southern Islands, Sea Islands and Volcanic Islands families of GPUs. On GFX6-8, the GFX block can only use pre-determined tiling modes which are programmed by the kernel according to the tiling mode table. GFX6 uses the GB_TILE_MODE0...31 registers, and GFX7-8 also has GB_MACROTILE_MODE0...15 registers. DCC is also supported on GFX8, albeit not displayable. Note that the tiling table is uAPI and userspace relies on specific modes being present at specific indices. How the tiling works is primarily determined by the so-called array mode. Use the TILE field to specify the array mode. Pixel data is organized into micro tiles. Each micro tile may be 8x8 / 8x8x4 / 8x8x8 pixels, depending on the array mode. Add the MICROTILE field to specify microtile mode. Microtiles may be further organized into macro tiles, which have many configurable parameters. Macro tile mode selection depends on how many bits per pixel an image has. Add the PIPE_CONFIG, TILE_SPLIT, BANK_WIDTH, BANK_HEIGHT, MACRO_TILE_ASPECT, NUM_BANKS fields to specify parameters of macro tiled modes. Furthermore, tiling is also influenced by memory configuration. Old RFC patches received feedback concerning that, so I looked into it specifically: GB_ADDR_CONFIG.ROW_SIZE needs to be considered when calculating TILE_SPLIT, but does not need to be included in the modifiers, and also PIPE_INTERLEAVE matters, but it's hardcoded to the same value on all GFX6-8 GPUs and changing it would break userspace, so let's assume it isn't going to change. Therefore we don't need to include that in modifiers. Mesa also reads NUM_RANKS but actually doesn't use its value on GFX6-8. As a side note, tiling works similarly on GFX4-5 (that is Evergreen and Northern Islands). But that will need some additional PIPE_CONFIG enum values as well as some extra fields not relevant to GFX6-8. Initially, let's only expose the tiling modes that are most relevant to sharing buffers between different processes: Exposed array modes (TILE field): - 1D_TILED_THIN1: micro tiled only - 2D_TILED_THIN1: macro tiled Exposed micro tile modes (MICROTILE field): - DISPLAY: supported by DCE (the display engine) - THIN: more efficient but not displayable Exposed macro tile modes: All possible parameters (25088 permutations). More modes may be exposed in the future as needed. Technically, the amount of possible combinations of all possible tiling parameters is in the range of hundreds of thousands, but in practice, there are just a handful of possible modifiers for a surface. For example on GFX8, a surface would have these modifiers, from best to worst performance: - 2D_TILED_THIN1 + THIN + DCC + macrotile params [1] - 2D_TILED_THIN1 + THIN + macrotile params [1] - 2D_TILED_THIN1 + DISPLAY + macrotile params [1] - 1D_TILED_THIN1 + THIN - 1D_TILED_THIN1 + DISPLAY - LINEAR [1] The macro tiling parameters depend on how many bits per pixel of the specific surface has and how the chip is configured. There is only one set of valid macrotile params for a given surface. DCC is only supported by GFX8 and newer, and only with non-displayable macrotiling modes. When sharing buffers between different GFX6-8 GPUs, it is very unlikely that they support the exact same macrotiling configuration, so they will likely need to use micro tiled modes, which are still much better than using linear buffers. (Note that currently Mesa always uses LINEAR when copying between two GPUs.) Suggested-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl> Signed-off-by: Timur Kristóf <timur.kristof@gmail.com> Reviewed-by: Marek Olšák <maraeo@gmail.com> Reviewed-by: Daniel Stone <daniels@collabora.com> Reviewed-by: Alex Deucher <alexander.deucher@amd.com> Acked-by: Christian König <christian.koenig@amd.com> Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Linux kernel ============ The Linux kernel is the core of any Linux operating system. It manages hardware, system resources, and provides the fundamental services for all other software. Quick Start ----------- * Report a bug: See Documentation/admin-guide/reporting-issues.rst * Get the latest kernel: https://kernel.org * Build the kernel: See Documentation/admin-guide/quickly-build-trimmed-linux.rst * Join the community: https://lore.kernel.org/ Essential Documentation ----------------------- All users should be familiar with: * Building requirements: Documentation/process/changes.rst * Code of Conduct: Documentation/process/code-of-conduct.rst * License: See COPYING Documentation can be built with make htmldocs or viewed online at: https://www.kernel.org/doc/html/latest/ Who Are You? ============ Find your role below: * New Kernel Developer - Getting started with kernel development * Academic Researcher - Studying kernel internals and architecture * Security Expert - Hardening and vulnerability analysis * Backport/Maintenance Engineer - Maintaining stable kernels * System Administrator - Configuring and troubleshooting * Maintainer - Leading subsystems and reviewing patches * Hardware Vendor - Writing drivers for new hardware * Distribution Maintainer - Packaging kernels for distros * AI Coding Assistant - LLMs and AI-powered development tools For Specific Users ================== New Kernel Developer -------------------- Welcome! Start your kernel development journey here: * Getting Started: Documentation/process/development-process.rst * Your First Patch: Documentation/process/submitting-patches.rst * Coding Style: Documentation/process/coding-style.rst * Build System: Documentation/kbuild/index.rst * Development Tools: Documentation/dev-tools/index.rst * Kernel Hacking Guide: Documentation/kernel-hacking/hacking.rst * Core APIs: Documentation/core-api/index.rst Academic Researcher ------------------- Explore the kernel's architecture and internals: * Researcher Guidelines: Documentation/process/researcher-guidelines.rst * Memory Management: Documentation/mm/index.rst * Scheduler: Documentation/scheduler/index.rst * Networking Stack: Documentation/networking/index.rst * Filesystems: Documentation/filesystems/index.rst * RCU (Read-Copy Update): Documentation/RCU/index.rst * Locking Primitives: Documentation/locking/index.rst * Power Management: Documentation/power/index.rst Security Expert --------------- Security documentation and hardening guides: * Security Documentation: Documentation/security/index.rst * LSM Development: Documentation/security/lsm-development.rst * Self Protection: Documentation/security/self-protection.rst * Reporting Vulnerabilities: Documentation/process/security-bugs.rst * CVE Procedures: Documentation/process/cve.rst * Embargoed Hardware Issues: Documentation/process/embargoed-hardware-issues.rst * Security Features: Documentation/userspace-api/seccomp_filter.rst Backport/Maintenance Engineer ----------------------------- Maintain and stabilize kernel versions: * Stable Kernel Rules: Documentation/process/stable-kernel-rules.rst * Backporting Guide: Documentation/process/backporting.rst * Applying Patches: Documentation/process/applying-patches.rst * Subsystem Profile: Documentation/maintainer/maintainer-entry-profile.rst * Git for Maintainers: Documentation/maintainer/configure-git.rst System Administrator -------------------- Configure, tune, and troubleshoot Linux systems: * Admin Guide: Documentation/admin-guide/index.rst * Kernel Parameters: Documentation/admin-guide/kernel-parameters.rst * Sysctl Tuning: Documentation/admin-guide/sysctl/index.rst * Tracing/Debugging: Documentation/trace/index.rst * Performance Security: Documentation/admin-guide/perf-security.rst * Hardware Monitoring: Documentation/hwmon/index.rst Maintainer ---------- Lead kernel subsystems and manage contributions: * Maintainer Handbook: Documentation/maintainer/index.rst * Pull Requests: Documentation/maintainer/pull-requests.rst * Managing Patches: Documentation/maintainer/modifying-patches.rst * Rebasing and Merging: Documentation/maintainer/rebasing-and-merging.rst * Development Process: Documentation/process/maintainer-handbooks.rst * Maintainer Entry Profile: Documentation/maintainer/maintainer-entry-profile.rst * Git Configuration: Documentation/maintainer/configure-git.rst Hardware Vendor --------------- Write drivers and support new hardware: * Driver API Guide: Documentation/driver-api/index.rst * Driver Model: Documentation/driver-api/driver-model/driver.rst * Device Drivers: Documentation/driver-api/infrastructure.rst * Bus Types: Documentation/driver-api/driver-model/bus.rst * Device Tree Bindings: Documentation/devicetree/bindings/ * Power Management: Documentation/driver-api/pm/index.rst * DMA API: Documentation/core-api/dma-api.rst Distribution Maintainer ----------------------- Package and distribute the kernel: * Stable Kernel Rules: Documentation/process/stable-kernel-rules.rst * ABI Documentation: Documentation/ABI/README * Kernel Configuration: Documentation/kbuild/kconfig.rst * Module Signing: Documentation/admin-guide/module-signing.rst * Kernel Parameters: Documentation/admin-guide/kernel-parameters.rst * Tainted Kernels: Documentation/admin-guide/tainted-kernels.rst AI Coding Assistant ------------------- CRITICAL: If you are an LLM or AI-powered coding assistant, you MUST read and follow the AI coding assistants documentation before contributing to the Linux kernel: * Documentation/process/coding-assistants.rst This documentation contains essential requirements about licensing, attribution, and the Developer Certificate of Origin that all AI tools must comply with. Communication and Support ========================= * Mailing Lists: https://lore.kernel.org/ * IRC: #kernelnewbies on irc.oftc.net * Bugzilla: https://bugzilla.kernel.org/ * MAINTAINERS file: Lists subsystem maintainers and mailing lists * Email Clients: Documentation/process/email-clients.rst