[RFC PATCH 0/7] 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.

* Only compilation tested so far (x86_64, defconfig + amdgpu enabled).
* No runtime validation yet.

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

Srinivasan Shanmugam (7):
  drm/amdgpu/uapi: add AMDGPU_GEM_DOMAIN_MMIO_REMAP
  drm/amdgpu: Add New TTM Placement - AMDGPU_PL_MMIO_REMAP and wire up
    plumbing
  drm/amdgpu: Plumbing for MMIO_REMAP memtype and user-visible strings
  drm/amdgpu: Add mmio_remap fields to amdgpu_device
  drm/amdgpu: Implement TTM handling for MMIO_REMAP placement
  drm/amdgpu: Create Singleton MMIO_REMAP BO and Initialize its pool
  drm/amdgpu: Return Handle to MMIO_REMAP Singleton for GEM Create

 drivers/gpu/drm/amd/amdgpu/amdgpu.h           |   7 ++
 drivers/gpu/drm/amd/amdgpu/amdgpu_fdinfo.c    |   1 +
 drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c       |  56 +++++++++
 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       | 112 +++++++++++++++++-
 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, 198 insertions(+), 8 deletions(-)

-- 
2.34.1