[RFC PATCH v2 0/8] drm/amdgpu: Add MMIO-remap Singleton BO for HDP flush

[Srinivasan Shanmugam]

This series introduces a kernel-managed singleton BO representing the
MMIO-remap (HDP flush) page and exposes it to userspace through a new
GEM domain.

Design
------
- A tiny (1-page) TTM bucket is introduced for AMDGPU_PL_MMIO_REMAP
  (mirroring doorbells).
- A singleton BO is created during amdgpu_ttm_init() and freed at
  fini().
- The BO is kernel-owned and never evicted.
- amdgpu_gem_create_ioctl() recognizes the new GEM domain bit
  (AMDGPU_GEM_DOMAIN_MMIO_REMAP) and returns a handle to the pre-created
singleton BO, enforcing size/alignment checks.
- Userspace thus gets a stable GEM handle and can mmap it to issue HDP
  flushes.

v2: Updated review comments from v1. (Alex/Christian)

* Only compilation tested so far (x86_64, defconfig + amdgpu enabled).

Cc: Christian König <christian.koenig at amd.com>
Cc: Alex Deucher <alexander.deucher at amd.com>

Srinivasan Shanmugam (8):
  drm/amdgpu/uapi: Introduce AMDGPU_GEM_DOMAIN_MMIO_REMAP
  drm/amdgpu/ttm: Add New AMDGPU_PL_MMIO_REMAP Placement
  drm/amdgpu: Wire up MMIO_REMAP placement and User-visible strings
  drm/amdgpu: Add mmio_remap bookkeeping to amdgpu_device
  drm/amdgpu: Implement TTM handling for MMIO_REMAP placement
  drm/amdgpu/ttm: Initialize AMDGPU_PL_MMIO_REMAP Heap
  drm/amdgpu/ttm: Allocate/Free 4K MMIO_REMAP Singleton BO
  drm/amdgpu/gem: Return Handle to MMIO_REMAP Singleton in GEM_CREATE

 drivers/gpu/drm/amd/amdgpu/amdgpu.h           |  1 +
 drivers/gpu/drm/amd/amdgpu/amdgpu_fdinfo.c    |  1 +
 drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c       | 62 ++++++++++++
 drivers/gpu/drm/amd/amdgpu/amdgpu_object.c    | 13 +++
 drivers/gpu/drm/amd/amdgpu/amdgpu_object.h    |  2 +
 .../gpu/drm/amd/amdgpu/amdgpu_res_cursor.h    |  2 +
 drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c       | 96 ++++++++++++++++++-
 drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h       |  3 +-
 include/drm/ttm/ttm_resource.h                |  2 +-
 include/uapi/drm/amdgpu_drm.h                 |  8 +-
 10 files changed, 183 insertions(+), 7 deletions(-)


base-commit: 6b70b6008d812a9a210455dd55459a21279bad1e
-- 
2.34.1