1 / 49

Tizen Linux Kernel

Tizen Linux Kernel. Sungkyunkwan University. Tizen Kernel Additional features. Memory Management CMA (Contiguous Memory Allocator), IOMMU, dma_buf, DRM (Direct Rendering Manager) ARM Linux has no DMA_ZONE on buddy

estradaf
Download Presentation

Tizen Linux Kernel

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Tizen Linux Kernel Sungkyunkwan University

  2. Tizen Kernel Additional features • Memory Management • CMA (Contiguous Memory Allocator), IOMMU, dma_buf, DRM (Direct Rendering Manager) • ARM Linux has no DMA_ZONE on buddy • Some devices require physically contiguous memory (CMA), other devices has IOMMU thus be able to use non-contiguous memory • Sharing DMA memory buffer for D/D to user • Power management (CPUfreq, Devfreq, PM-QoS, Charger-manager) • KDBUS • V4L2 (Video for Linux 2) • EXTCON

  3. Previous Reference Kernel • Linux 3.0.15 • Obsolete LTS (Current: 3.4 & 3.10) • Support RD-PQ (Tizen 2) & RD-210 (tizen 1 & 2) • RD-PQ: Exynos4412 • RD-210: Exynos 4210 (Linux 2.6.36 for Tizen 1) • Not Good as Reference • Too many backported features. • Too OLD! No LTS/LTSI support • Many kernel hacks & dirty patches • git history removed. • Forked from production kernel. • Hard to read

  4. Status of Tizen Reference Kernels • Two reference kernels: ARM/Intel • ARM (armv7, aarch64) • Linux 3.10.y • 3.10.33 @ 2014/05 • Full git history • Armv6 support (Raspberry Pi) Coming soon. • Test & validation phase (integration test with userspace) • Intel (x86, x86_64) • Linux 3.14.1 • Recent ATOM Soc support merged

  5. Tizen Kernel Overview

  6. Tizen Kernel Overview (cont)

  7. Tizen Memory Management

  8. Tizen Memory Management • Coupled with Graphics & Multimedia devices • Graphics & Multimedia devices = DMA devices with HUGE Buffers

  9. What is DRM • DRM is not Digital Right Management • Direct Rendering Manager • Kernel-level graphics device driver that support Direct Rendering Infrastructure. • Direct Rendering • An application communicates directly with graphics device driver • Display mode setting • Graphics memory management

  10. Why DRM • Can give display experiences similar to PC environment. • Why not use DRM until now? • DRM was designed for PC • Embedded System • Low performance • No dedicated graphics memory • Not one graphics card but separated hardware devices • Linux frame buffer driver

  11. Why DRM (cont) • Changed embedded environment • Powerful embedded SoCs • Requirements • Display hotplug & clone, exteded mode • Unified memory management • Direct rendering • Varying device control with common interface

  12. DRM of Tizen kernel • Currently, DRM support is only for Exynos SoCs. (ARM based) • Need Exynos specific DRM driver • Exynos DRM driver • To support graphics hardware of Exynos SoCs • First ARM SoC graphics driver to use the DRM • Merged into the mainline linux 3.2 kernel • linux/drivers/gpu/drm/exynos

  13. Graphics (DRM / GEM) • Graphics: • DRM (Direct Rendering Manager) / GEM (Graphics Execution Manager) • GEM • Framework developed by Intel • To manage graphics memory • Framework for buffer management • Allocation and sharing

  14. DRM / GEM Allocation GEM Allocation steps @ Tizen (Generic) • DRM_IOCTL_MODE_CREATE_DUMB • Create GEM object(global) & user GEM handle(per process) • dumb_create() of struct drm_driver • No physical memory allocated. • DRM_IOCTL_MODE_MAP_DUMB • Create fake mmap offset of a gem object and relay the object to user • A hash key of the gem object. • dumb_map_offset() of struct drm_driver • MMAP • Request mmap based on the hash key as the offset • Create user address space • Setup cache attribute. • Not mapped to physical memory, yet

  15. DRM / GEM Allocation (cont) GEM Allocation steps @ Tizen (Generic) • On-demand Paging • Implement & Register a fault handler that • With a page fault, allocate a page and map the page. • vma->vm_ops->fault = xxx_drm_gem_fault • Use! • DRM_IOCTL_MODE_DESTROY_DUMB • Remove GEM handle & object • Free memory • Implement dumb_destroy() of struct drm_driver

  16. DRM / GEM Allocation (cont) GEM Allocation steps @ Tizen (Exynos Only) • DRM_IOCTL_EXYNOS_GEM_CREATE • Only use user-desired size and buffer types. • Create gem object(global) & user gem handle(per process) • physical memory allocated. • DRM_IOCTL_EXYNOS_GEM_MMAP • Create user address space • Map the user address space to physical memory • LIBDRM of Exynos uses these APIs, not the generic.

  17. DRM / GEM Sharing GEM Sharing @ Tizen • DRM_IOCTL_GEM_FLINK • “I will share this GEM to others.” • Create GEM object name for the given GEM handle • Global key vaue for sharing • DRM_IOCTL_GEM_OPEN • “I want to use the shared GEM.” • Create GEM handle based on the given GEM object name • DRM_IOCTL_GEM_CLOSE

  18. Tizen Kernel MM –Multimedia (V4L2 / VB2)

  19. V4L2 / VB2 • Tizen recommends to use V4L2 at Tizen kernel for Multimedia devices • Video input (codec & camera) & Radio • However, as long as the kernel has..: • Gstreamer/OpenMAX plugins • A method to share with other F/W via DMABUF of UMM • If V4L2/VB2 is used, things get easier.

  20. Tizen Kernel MM –OpenGL / G3D-GPU

  21. OpenGL / G3D-GPU • Most ARM SoC GPUs (MALI, SGX, …) use their own memory manager • E.g., Exynos4412/4210 Tizen Reference Kernel has Mali w/ UMM. • Mali DDK modified to be compatible with UMM-DMABUF. • If GPU drivers use DRM, it would be great. • (and make them GPL)

  22. Graphic and Display Usage Scenario

  23. Graphic and Display Usage Scenario

  24. Graphic and Display Usage Scenario

  25. Graphic and Display Usage Scenario

  26. Graphic and Display Usage Scenario

  27. Tizen kernel Buffer Sharing

  28. Tizen Kernel Buffer Sharing (cont) • Requirement from Tizen platform and hardware • Different Memory Managers: GEM, VB2, GPU-adhoc, … • Share buffers • w/o memcpy • From and to users • Never expose directly to users (e.g., physical address) UMM DMABUF!

  29. Unified Memory Management (UMM) • Introduced by Jesse Barker, 2011 • Includes • DMABUF (sharing buffer) • Export • GEM/VB2/… object  DMABUF • Import • DMABUF  GEM/VB2/… object • Userspace sees DMABUF as a File Descriptor • DMA mapping API for allocation • CMA (Contiguous Memory Allocator) • IOMMU (MMU for I/O devs)

  30. DMA Buffer Sharing: Camera  Display

  31. DMA Buffer Sharing Example • Camera App 1)Request V4L2 camera buffer (U) 2)Allocate CMA buffer (K) 3)Request a camera frame at the V4L2 buffer (U) 4)Store the camera frame & Notify user (K) 5)Request DMABUF export for the V4L2 camera buffer (U) 6)dma_buf_exporter() (K) • Create DMABUF from V4L2 buffer 7)dma_buf_fd() (K) • Provide FD of the DMABUF to user

  32. DMA Buffer Sharing Example (cont) • Camera App 1)Request V4L2 camera buffer (U) 2)Allocate CMA buffer (K) 3)Request a camera frame at the V4L2 buffer (U) 4)Store the camera frame & Notify user (K) 5)Request DMABUF export for the V4L2 camera buffer (U) 6)dma_buf_exporter() (K) • Create DMABUF from V4L2 buffer 7)dma_buf_fd() (K) • Provide FD of the DMABUF to user

  33. DMA Buffer Sharing Example (cont) • Camera App 1)Request V4L2 camera buffer (U) 2)Allocate CMA buffer (K) 3)Request a camera frame at the V4L2 buffer (U) 4)Store the camera frame & Notify user (K) 5)Request DMABUF export for the V4L2 camera buffer (U) 6)dma_buf_exporter() (K) • Create DMABUF from V4L2 buffer 7)dma_buf_fd() (K) • Provide FD of the DMABUF to user

  34. DMA Buffer Sharing Example (cont) • Camera App 8)Request FD->GEM conversion (U) 9)dma_buf_get(fd) (K) • Get DMABUF from FD 10)dma_buf_attach(dma-buf) / dma_buf_map_attachment() (K) • Get Buffer from DMABUF 11)Import as GEM, send user (K) 12)Request GEM object name (U) 13)Return GEM object name (K) 14)Send GEM object name to X (U)

  35. DMA Buffer Sharing Example (cont) • Camera App 8)Request FD->GEM conversion (U) 9)dma_buf_get(fd) (K) • Get DMABUF from FD 10)dma_buf_attach(dma-buf) / dma_buf_map_attachment() (K) • Get Buffer from DMABUF 11)Import as GEM, send user (K) 12)Request GEM object name (U) 13)Return GEM object name (K) 14)Send GEM object name to X (U)

  36. DMA Buffer Sharing Example (cont) • X server 15)Convert given GEM object name to GEM. Display its content. (U & K)

  37. DMA Buffer Sharing Example (cont) • Close after usage 1)“Free” the GEM object (U) 2)Remove reference from the DMABUF (K) 3)Close(DMABUF-FD) at cam app (U) 4)(No more reference to DMABUF) Release callback executed (K)

  38. Buffer Synchronization

  39. Problem Definition • Simple Usage Scenario • 1. CPU writes to buffer1. • 2. CPU tells GPU to do something on buffer1. • 3. GPU does something on buffer1. • GPU finishes. • 4. CPU reads the buffer1 How to ensure CPU won’t use buffer 1 until step 4? CPU GPU 2 1 BUS 4 3 DRAM

  40. Problem Definition (cont) • What if there are two threads using GPU? • And if the two look at the same buffer? • Not even aware of it? • What if the two DMA devices (GPU, FIMC) share buffer? • But hard to know it at drivers or user threads. • FIMC never knows when GPU finishes • FIMC never knows when Threads1 stops using “buffer1” • Threads2 never know when GPU stops using “buffer1”

  41. Buffer Synchronization • TGL (Tizen Global Lock) @ Tizen 2.0 • … Let userspace handle the issue … • Kernel patch required. • Sync Framework (Google) • Jun, 2012. Resources w/o DMABUF (similar with TGL) • KDS (Kernel Dependency System, ARM) • May 2012 / DMABUF-compatible • DMA Fence Framework (Canonical/TI) • Aug 2012 / DMABUF-compatible • Work-In-Progress

  42. K-dbus

  43. Kdbus –D-bus is? • D-Bus • Message bus system • Method Call transaction • Signals • Broadcasting

  44. Kdbus –K-dbus is? • Low-level, native kernel D-Bus transport • All communication between processes take place over special character device nodes in /dev/kdbus • Receiver buffers • Single copy to destinations • memfds • File descriptor for memory regions • Zero copy implementation

  45. D-bus vs Kdbus

  46. Others

  47. EXTCON (External Connector) • Yet Another Weird Ad-hoc Kernel Hacks Removed • Manage status of cable & ports • A port with multiple cables (docks, multi-cables, …) • A port with multiple modes (USB, HDMI, TA, …) • 3.5pi: stereo, stereo+mic, stereo+mic+buttons, stereo+buttons, mono, … • Compatible with Switch • Android Switch drivers can be easily ported • Refer to Linux/Documentation (porting guide for switch driver) • Extcon drivers export both Switch and Extcon interfaces (compat mode) • In Reference Device • MUIC (USB+HDMI+TA+DOCK+…) • 3.5Pi Jack

  48. Charger • Charger Manager (/drivers/power/charger-manager.c) • All needed by Tizen user space are prepared • No OAL modification required • OR supply battery/charger interface with power-supply-class • Use EXTCON for Cable-Input (MUIC in mobile) • Switch class is no longer available in Linux. • Note: some SOC (state-of-charge) value is required for mobile profile. Unless, Tizen will assume that SOC is 0 Shutdown!

  49. Power Management • Recommendation For Tizen3.0 or later • Do not use DVFS (CPUfreq/Devfreq) min/max ABIs • PASS (Power-Aware System Service in Deviced) uses • Use (keep their standard ABIs for PASS) • CPUfreq& Devfreq(DVFS for non CPU devices if you have them) • Thermal FW • PASS gives hints to DVFS/Hotplug • based on the info from user space. • based on the other kernel ABIs (e.g., Thermal) • highly configurable. (control knob of performance & power)

More Related