gpu: nvgpu: Add semaphore based gk20a_channel_sync

Add semaphore implementation of the gk20a_channel_sync interface.

Each channel has one semaphore pool, which is mapped as read-write to
the channel vm. We allocate one or two semaphores from the pool for each
submit.

The first semaphore is only needed if we need to wait for an opaque sync
fd. In that case, we allocate the semaphore, and ask GPU to wait for
it's value to become 1 (semaphore acquire method).  We also queue a
kernel work that waits on the fence fd, and subsequently releases the
semaphore (sets its value to 1) so that the command buffer can proceed.

The second semaphore is used on every submit, and is used for work
completion tracking. The GPU sets its value to 1 when the command buffer
has been processed.

The channel jobs need to hold references to both semaphores so that
their backing semaphore pool slots are not reused while the job is in
flight. Therefore gk20a_channel_fence will keep a reference to the
semaphore that it represents (channel fences are stored in the job
structure). This means that we must diligently close and dup the
gk20a_channel_fence objects to avoid leaking semaphores.

Bug 1450122
Bug 1445450

Change-Id: Ib61091a1b7632fa36efe0289011040ef7c4ae8f8
Signed-off-by: Lauri Peltonen <lpeltonen@nvidia.com>
Reviewed-on: http://git-master/r/374844
GVS: Gerrit_Virtual_Submit
Reviewed-by: Terje Bergstrom <tbergstrom@nvidia.com>

0 files changed, 0 insertions, 0 deletions