cachepc-linux

driver-core.rst (6722B)

============================
 Core Driver Infrastructure
============================

GPU Hardware Structure
======================

Each ASIC is a collection of hardware blocks.  We refer to them as
"IPs" (Intellectual Property blocks).  Each IP encapsulates certain
functionality. IPs are versioned and can also be mixed and matched.
E.g., you might have two different ASICs that both have System DMA (SDMA) 5.x IPs.
The driver is arranged by IPs.  There are driver components to handle
the initialization and operation of each IP.  There are also a bunch
of smaller IPs that don't really need much if any driver interaction.
Those end up getting lumped into the common stuff in the soc files.
The soc files (e.g., vi.c, soc15.c nv.c) contain code for aspects of
the SoC itself rather than specific IPs.  E.g., things like GPU resets
and register access functions are SoC dependent.

An APU contains more than just CPU and GPU, it also contains all of
the platform stuff (audio, usb, gpio, etc.).  Also, a lot of
components are shared between the CPU, platform, and the GPU (e.g.,
SMU, PSP, etc.).  Specific components (CPU, GPU, etc.) usually have
their interface to interact with those common components.  For things
like S0i3 there is a ton of coordination required across all the
components, but that is probably a bit beyond the scope of this
section.

With respect to the GPU, we have the following major IPs:

GMC (Graphics Memory Controller)
    This was a dedicated IP on older pre-vega chips, but has since
    become somewhat decentralized on vega and newer chips.  They now
    have dedicated memory hubs for specific IPs or groups of IPs.  We
    still treat it as a single component in the driver however since
    the programming model is still pretty similar.  This is how the
    different IPs on the GPU get the memory (VRAM or system memory).
    It also provides the support for per process GPU virtual address
    spaces.

IH (Interrupt Handler)
    This is the interrupt controller on the GPU.  All of the IPs feed
    their interrupts into this IP and it aggregates them into a set of
    ring buffers that the driver can parse to handle interrupts from
    different IPs.

PSP (Platform Security Processor)
    This handles security policy for the SoC and executes trusted
    applications, and validates and loads firmwares for other blocks.

SMU (System Management Unit)
    This is the power management microcontroller.  It manages the entire
    SoC.  The driver interacts with it to control power management
    features like clocks, voltages, power rails, etc.

DCN (Display Controller Next)
    This is the display controller.  It handles the display hardware.
    It is described in more details in :ref:`Display Core <amdgpu-display-core>`.

SDMA (System DMA)
    This is a multi-purpose DMA engine.  The kernel driver uses it for
    various things including paging and GPU page table updates.  It's also
    exposed to userspace for use by user mode drivers (OpenGL, Vulkan,
    etc.)

GC (Graphics and Compute)
    This is the graphics and compute engine, i.e., the block that
    encompasses the 3D pipeline and and shader blocks.  This is by far the
    largest block on the GPU.  The 3D pipeline has tons of sub-blocks.  In
    addition to that, it also contains the CP microcontrollers (ME, PFP,
    CE, MEC) and the RLC microcontroller.  It's exposed to userspace for
    user mode drivers (OpenGL, Vulkan, OpenCL, etc.)

VCN (Video Core Next)
    This is the multi-media engine.  It handles video and image encode and
    decode.  It's exposed to userspace for user mode drivers (VA-API,
    OpenMAX, etc.)

Graphics and Compute Microcontrollers
-------------------------------------

CP (Command Processor)
    The name for the hardware block that encompasses the front end of the
    GFX/Compute pipeline.  Consists mainly of a bunch of microcontrollers
    (PFP, ME, CE, MEC).  The firmware that runs on these microcontrollers
    provides the driver interface to interact with the GFX/Compute engine.

    MEC (MicroEngine Compute)
        This is the microcontroller that controls the compute queues on the
        GFX/compute engine.

    MES (MicroEngine Scheduler)
        This is a new engine for managing queues.  This is currently unused.

RLC (RunList Controller)
    This is another microcontroller in the GFX/Compute engine.  It handles
    power management related functionality within the GFX/Compute engine.
    The name is a vestige of old hardware where it was originally added
    and doesn't really have much relation to what the engine does now.

Driver Structure
================

In general, the driver has a list of all of the IPs on a particular
SoC and for things like init/fini/suspend/resume, more or less just
walks the list and handles each IP.

Some useful constructs:

KIQ (Kernel Interface Queue)
    This is a control queue used by the kernel driver to manage other gfx
    and compute queues on the GFX/compute engine.  You can use it to
    map/unmap additional queues, etc.

IB (Indirect Buffer)
    A command buffer for a particular engine.  Rather than writing
    commands directly to the queue, you can write the commands into a
    piece of memory and then put a pointer to the memory into the queue.
    The hardware will then follow the pointer and execute the commands in
    the memory, then returning to the rest of the commands in the ring.

.. _amdgpu_memory_domains:

Memory Domains
==============

.. kernel-doc:: include/uapi/drm/amdgpu_drm.h
   :doc: memory domains

Buffer Objects
==============

.. kernel-doc:: drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
   :doc: amdgpu_object

.. kernel-doc:: drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
   :internal:

PRIME Buffer Sharing
====================

.. kernel-doc:: drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c
   :doc: PRIME Buffer Sharing

.. kernel-doc:: drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c
   :internal:

MMU Notifier
============

.. kernel-doc:: drivers/gpu/drm/amd/amdgpu/amdgpu_mn.c
   :doc: MMU Notifier

.. kernel-doc:: drivers/gpu/drm/amd/amdgpu/amdgpu_mn.c
   :internal:

AMDGPU Virtual Memory
=====================

.. kernel-doc:: drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
   :doc: GPUVM

.. kernel-doc:: drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
   :internal:

Interrupt Handling
==================

.. kernel-doc:: drivers/gpu/drm/amd/amdgpu/amdgpu_irq.c
   :doc: Interrupt Handling

.. kernel-doc:: drivers/gpu/drm/amd/amdgpu/amdgpu_irq.c
   :internal:

IP Blocks
=========

.. kernel-doc:: drivers/gpu/drm/amd/include/amd_shared.h
   :doc: IP Blocks

.. kernel-doc:: drivers/gpu/drm/amd/include/amd_shared.h
   :identifiers: amd_ip_block_type amd_ip_funcs