[PATCH 2/3] Documentation/gpu: include description of AMDGPU hardware structure

[Yann Dirson]

This is Alex' description from the "gpu block diagram" thread, edited to
fit as ReST.

Originally-by: Alex Deucher <alexander.deucher at amd.com>
Signed-off-by: Yann Dirson <ydirson at free.fr>
---
 Documentation/gpu/amdgpu/driver-core.rst | 81 ++++++++++++++++++++++++
 1 file changed, 81 insertions(+)

diff --git a/Documentation/gpu/amdgpu/driver-core.rst b/Documentation/gpu/amdgpu/driver-core.rst
index 97f9a9b68924..909b13fad6a8 100644
--- a/Documentation/gpu/amdgpu/driver-core.rst
+++ b/Documentation/gpu/amdgpu/driver-core.rst
@@ -2,6 +2,87 @@
  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 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.
+
+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.  The 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.)
+
+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.
+
+
 .. _amdgpu_memory_domains:
 
 Memory Domains
-- 
2.31.1