drm/amd/display: Initial documentation for AMDgpu DC

[Why]
Documentation is helpful for the community to understand our code.
This change does some high-level documentation of some DM interfaces
with DRM, and the amdgpu base driver.

[How]
An entry for AMDgpu DC has been added to Documentation/gpu/drivers.rst
TOC. amdgpu-dc.rst is created to pull in inline doc-strings, which:
- Provides an overview for "What is DM?"
- Documents AMDgpu DM lifecyle
- Documents IRQ management
- Documents atomic_check and commit_tail interfaces

Signed-off-by: Leo Li <sunpeng.li@amd.com>
Reviewed-by: David Francis <David.Francis@amd.com>
Acked-by: Leo Li <sunpeng.li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

Documentation/gpu/amdgpu-dc.rst

@@ -0,0 +1,68 @@
+===================================
+drm/amd/display - Display Core (DC)
+===================================
+
+*placeholder - general description of supported platforms, what dc is, etc.*
+
+Because it is partially shared with other operating systems, the Display Core
+Driver is divided in two pieces.
+
+1. **Display Core (DC)** contains the OS-agnostic components. Things like
+   hardware programming and resource management are handled here.
+2. **Display Manager (DM)** contains the OS-dependent components. Hooks to the
+   amdgpu base driver and DRM are implemented here.
+
+It doesn't help that the entire package is frequently referred to as DC. But
+with the context in mind, it should be clear.
+
+When CONFIG_DRM_AMD_DC is enabled, DC will be initialized by default for
+supported ASICs. To force disable, set `amdgpu.dc=0` on kernel command line.
+Likewise, to force enable on unsupported ASICs, set `amdgpu.dc=1`.
+
+To determine if DC is loaded, search dmesg for the following entry:
+
+``Display Core initialized with <version number here>``
+
+AMDgpu Display Manager
+======================
+
+.. kernel-doc:: drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+   :doc: overview
+
+.. kernel-doc:: drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h
+   :internal:
+
+Lifecycle
+---------
+
+.. kernel-doc:: drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+   :doc: DM Lifecycle
+
+.. kernel-doc:: drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+   :functions: dm_hw_init dm_hw_fini
+
+Interrupts
+----------
+
+.. kernel-doc:: drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_irq.c
+   :doc: overview
+
+.. kernel-doc:: drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_irq.c
+   :internal:
+
+.. kernel-doc:: drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+   :functions: register_hpd_handlers dm_crtc_high_irq dm_pflip_high_irq
+
+Atomic Implementation
+---------------------
+
+.. kernel-doc:: drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+   :doc: atomic
+
+.. kernel-doc:: drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+   :functions: amdgpu_dm_atomic_check amdgpu_dm_atomic_commit_tail
+
+Display Core
+============
+
+**WIP**

Documentation/gpu/drivers.rst

@@ -5,6 +5,7 @@ GPU Driver Documentation
 .. toctree::
 
    amdgpu
+   amdgpu-dc
    i915
    meson
    pl111