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60b5fa6edf
Replace the gem-vram memory manager with gem-shmem. Makes the driver more robust and enables dma-buf sharing with other hardware. Gem-vram was created from various drivers that used TTM for their memory management. All these drivers have meanwhile been converted to gem-shmem. Using gem-vram is deprecated because it has several problems. * TTM requires significant overcommitment of video memory for reliable page flips. There needs to be 3 times the size of the largest possible framebuffer available or page flips can fail. This leaves the display dark without further warning. Hibmc hardware with 32 MiB and a maximum framebuffer size of 1920x2000 is at the limit. * No dma-buf sharing without GTT support. Neither gem-vram nor hibmc hardware support a GTT address space. This is required to share buffers with other devices via dma-buf interfaces. * TTM requires hardware-accelerated rendering into video memory for optimal results. As hibmc hardware cannot do this, hibmc renders in system memory and copies the result to video memory. This can be more effectively implemented with gem-shmem and DRM's shadow-plane helpers. Converting hibmc to gem-shmem and shadow-plane helpers. * Replace gem-vram entry points in struct drm_driver with gem-shmem equivalents. This makes the driver allocate struct drm_gem_shmem_object for its buffers. * Use DRM_GEM_SHADOW_*_PLANE for its plane funcs and plane-helper funcs. The shadow-plane helpers map a plane's gem buffer objects into kernel address space during a page flip, so that atomic_update can copy them to video memory. * Handle framebuffer damage in hibmc_plane_atomic_update(). This updates video memory from the plane's framebuffer. It automatically synchronizes shared buffers with other devices. Create the framebuffer with drm_gem_fb_create_with_dirty() to trigger the update on each page flip. * Initialize the plane with drm_plane_enable_fb_damage_clips() to limit the damage updates to the framebuffer areas that changed. We don't want to do a full-buffer memcpy if only a small area has changed. * Test display modes against the available video memory in hibmc_mode_config_mode_valid(). We only want to announce display modes that fit into display memory. * Map the display memory itself into kernel address space. * Do not set drm_mode_config.prefer_shadow. This would advise user space to install a shadow buffer. But with gem-shmem, the gem buffer object already acts as a shadow buffer for video memory. We use these patterns in many other drivers with similar limitation as hibmc and its hardware. With these changes in place, hibmc is more robust and better integrated into the overall DRM framework. v3: - fix coding style v2: - do not select TTM symbols Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de> Reviewed-by: Yongbang Shi <shiyongbang@huawei.com> Link: https://patch.msgid.link/20260618123142.92298-7-tzimmermann@suse.de |
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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