Am 14.12.21 um 10:44 schrieb Huang, Ray:
[AMD Official Use Only]
-----Original Message-----
From: Koenig, Christian <Christian.Koenig@xxxxxxx>
Sent: Tuesday, December 14, 2021 5:24 PM
To: Huang, Ray <Ray.Huang@xxxxxxx>; dri-devel@xxxxxxxxxxxxxxxxxxxxx;
Daniel Vetter <daniel.vetter@xxxxxxxx>; Sumit Semwal
<sumit.semwal@xxxxxxxxxx>
Cc: amd-gfx@xxxxxxxxxxxxxxxxxxxxx; linux-media@xxxxxxxxxxxxxxx; Deucher,
Alexander <Alexander.Deucher@xxxxxxx>; Liu, Monk
<Monk.Liu@xxxxxxx>
Subject: Re: [PATCH 1/3] dma-buf: make the flags can be configured during
dma fence init
Am 14.12.21 um 10:19 schrieb Huang, Ray:
[AMD Official Use Only]
-----Original Message-----
From: Koenig, Christian <Christian.Koenig@xxxxxxx>
Sent: Tuesday, December 14, 2021 4:00 PM
To: Huang, Ray <Ray.Huang@xxxxxxx>; dri-devel@xxxxxxxxxxxxxxxxxxxxx;
Daniel Vetter <daniel.vetter@xxxxxxxx>; Sumit Semwal
<sumit.semwal@xxxxxxxxxx>
Cc: amd-gfx@xxxxxxxxxxxxxxxxxxxxx; linux-media@xxxxxxxxxxxxxxx;
Deucher, Alexander <Alexander.Deucher@xxxxxxx>; Liu, Monk
<Monk.Liu@xxxxxxx>
Subject: Re: [PATCH 1/3] dma-buf: make the flags can be configured
during dma fence init
Am 13.12.21 um 07:34 schrieb Huang Rui:
In some user scenarios, the get_timeline_name callback uses the
flags to decide which way to return the timeline string name. Once
the trace_dma_fence_init event is enabled, it will call
get_timeline_name callback to dump the fence structure. However, at
this moment, the flags are always 0, and it might trigger some
issues in get_timeline_name callback implementation of different gpu
driver. So make a member to initialize the flags in dma_fence_init().
Well that doesn't make much sense to me.
None of the dma_fence callbacks is called from the dma_fence_init
function (or at least shouldn't). So drivers always have the
opportunity to to adjust the flags.
So please explain the rational again?
Once we enable trace_dma_fence_init event, we will call get_driver_name
and get_timeline_name callback function to dump the names in
dma_fence_init().
At that time, the flags are always 0. However, in
amdgpu_fence_get_timeline_name(), it will check the flags
(AMDGPU_FENCE_FLAG_EMBED_IN_JOB_BIT) to select which way to get
the ring.
If the fence should be actually embedded in the job (will be set after that),
it still will trigger a kernel panic (please see patch2) because it go with a
wrong way. Because we cannot set the flags at the start of dma_fence_init.
That is the problem.
Well then I think we should fix the whole approach instead because what
you try to do here is utterly nonsense. You can't modify the ops structure on
the fly because that is used by all the fences.
Instead please just duplicate the amdgpu_fence_ops() and separate them
into two structure, one for each case.
This way we should also be able to completely drop the
AMDGPU_FENCE_FLAG_EMBED_IN_JOB_BIT flag.
OK, you mean this flag is not one of them in standard dma_fence_flag_bits and it AMD specific, so we would better to drop this to align the dam_fence structure design?
Well yes and no. We can use driver private flags, it's just that for
this use case it doesn't make much sense.
See what the functions do, for example amdgpu_fence_enable_signaling():
if (test_bit(AMDGPU_FENCE_FLAG_EMBED_IN_JOB_BIT, &f->flags)) {
struct amdgpu_job *job = container_of(f, struct
amdgpu_job, hw_fence);
ring = to_amdgpu_ring(job->base.sched);
} else {
ring = to_amdgpu_fence(f)->ring;
}
if (!timer_pending(&ring->fence_drv.fallback_timer))
amdgpu_fence_schedule_fallback(ring);
return true;
That can much cleaner be done as
static bool amdgpu_fence_enable_signaling(struct dma_fence *f)
{
if (!timer_pending(&ring->fence_drv.fallback_timer))
amdgpu_fence_schedule_fallback(to_amdgpu_fence(f)->ring);
return true;
}
static bool amdgpu_job_fence_enable_signaling(struct dma_fence *f)
{
....
}
If we want to avoid the duplication of logic we should just move the
timer_pending() check into a separate function.
Regards,
Christian.
Thanks,
Ray
Regards,
Christian.
Thanks,
Ray
Christian.
Signed-off-by: Huang Rui <ray.huang@xxxxxxx>
---
drivers/dma-buf/dma-fence.c | 2 +-
include/linux/dma-fence.h | 7 +++++++
2 files changed, 8 insertions(+), 1 deletion(-)
diff --git a/drivers/dma-buf/dma-fence.c
b/drivers/dma-buf/dma-fence.c index 066400ed8841..3e0622bf385f
100644
--- a/drivers/dma-buf/dma-fence.c
+++ b/drivers/dma-buf/dma-fence.c
@@ -952,7 +952,7 @@ dma_fence_init(struct dma_fence *fence, const
struct dma_fence_ops *ops,
fence->lock = lock;
fence->context = context;
fence->seqno = seqno;
- fence->flags = 0UL;
+ fence->flags = ops->init_flags;
fence->error = 0;
trace_dma_fence_init(fence);
diff --git a/include/linux/dma-fence.h b/include/linux/dma-fence.h
index 1ea691753bd3..f9270c5bc07a 100644
--- a/include/linux/dma-fence.h
+++ b/include/linux/dma-fence.h
@@ -131,6 +131,13 @@ struct dma_fence_ops {
*/
bool use_64bit_seqno;
+ /**
+ * @init_flags:
+ *
+ * The initial value of fence flags (A mask of DMA_FENCE_FLAG_*
defined).
+ */
+ unsigned long init_flags;
+
/**
* @get_driver_name:
*
