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

[Christian König]

Am 06.12.24 um 14:12 schrieb 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.

Just FYI, you duplicated the text somehow :)

>
> 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.

I actually pushed to remove drm_gem_lock_reservations() in favor of 
using the drm_exec object.

It would be nice if you could use that one instead.

Regards,
Christian.

>
> * 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(-)
>