[PATCH 0/4] drm/vc4: Clean-up the BO seqnos

[Maíra Canal]

This series introduces a series of clean-ups in BO reservations for the
VC4 driver. Currently, VC4 uses shared fences to track BO reservations as
several other DRM devices. But apart from the DMA reservation objects, VC4
also attaches seqnos to its BOs with the intention to track if the job that
uses such BO has finished.

The seqno tracking system was introduced before the DMA reservation objects
and we ended up lefting it in the code after DMA resv was introduced. This
is redundant, as we can perfectly track the end of a job with a fence.
Therefore, this series focuses on eliminating the seqnos from the BO.

This series introduces a series of clean-ups for BO reservations in the VC4
driver. Currently, VC4 uses shared fences to track BO reservations, similar
to many other DRM devices. However, in addition to DMA reservation objects,
VC4 has been maintaining a separate seqno tracking system for BOs to track
job completion.

The seqno tracking system was implemented before DMA reservation objects
and was left in the code after DMA reservation's introduction. This
approach is now redundant, as job completion can be effectively tracked
using fences. Consequently, this series focuses on eliminating seqnos from
the BO implementation.

Patch Breakdown
===============

* Patch #1: Uses the DRM GEM implementation of `drm_gem_lock_reservations()`
and `drm_gem_unlock_reservations()` to replace the open-coded implementation
of this functions by VC4. A straightforward change with no functional
changes.

* Patch #2: Implements the VC4 wait BO IOCTL using DMA reservations. The
new implementation closely mirrors the V3D approach and removes the IOCTL's
dependency on BO sequence numbers.

* Patch #3: The central piece of this patchset. It removes `bo->seqno`,
`bo->write_seqno`, and `exec->bin_dep_seqno` from the driver. As the seqno
tracking system is redundant, its deletion is relatively straightforward.
The only notable change is `vc4_async_set_fence_cb()`, which now uses
`dma_fence_add_callback()` to add the VC4 callback.

* Patch #4: Deletes the now-unused function `vc4_queue_seqno_cb()`.

Best Regards,
- Maíra

Maíra Canal (4):
  drm/vc4: Use `drm_gem_lock_reservations()` instead of hard-coding
  drm/vc4: Use DMA Resv to implement VC4 wait BO IOCTL
  drm/vc4: Remove BOs seqnos
  drm/vc4: Remove `vc4_queue_seqno_cb()`

 drivers/gpu/drm/vc4/vc4_crtc.c     |  22 ++---
 drivers/gpu/drm/vc4/vc4_drv.h      |  26 ++---
 drivers/gpu/drm/vc4/vc4_gem.c      | 147 ++++++-----------------------
 drivers/gpu/drm/vc4/vc4_validate.c |  11 ---
 4 files changed, 48 insertions(+), 158 deletions(-)

-- 
2.47.1