On 30/09/2021 20:09, Boris Brezillon wrote:
Sometimes, all the user wants to do is add a synchronization point. Userspace can already do that by submitting a NULL job, but this implies submitting something to the GPU when we could simply skip the job and signal the done fence directly.
v5:
- New patch
Signed-off-by: Boris Brezillon boris.brezillon@collabora.com
I had thought we would be fine without kbase's "dependency only atom" because we don't have the fan-{in,out} problems that kbase's atoms produce. But if we're ending up with real hardware NULL jobs then this is clearly better.
A couple of minor points below, but as far as I can tell this is functionally correct.
Reviewed-by: Steven Price steven.price@arm.com
drivers/gpu/drm/panfrost/panfrost_drv.c | 9 +++++++-- drivers/gpu/drm/panfrost/panfrost_job.c | 6 ++++++ include/uapi/drm/panfrost_drm.h | 7 +++++++ 3 files changed, 20 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/panfrost/panfrost_drv.c b/drivers/gpu/drm/panfrost/panfrost_drv.c index 30dc158d56e6..89a0c484310c 100644 --- a/drivers/gpu/drm/panfrost/panfrost_drv.c +++ b/drivers/gpu/drm/panfrost/panfrost_drv.c @@ -542,7 +542,9 @@ static const struct panfrost_submit_ioctl_version_info submit_versions[] = { [1] = { 48, 8, 16 }, };
-#define PANFROST_JD_ALLOWED_REQS PANFROST_JD_REQ_FS +#define PANFROST_JD_ALLOWED_REQS \
- (PANFROST_JD_REQ_FS | \
PANFROST_JD_REQ_DEP_ONLY)static int panfrost_submit_job(struct drm_device *dev, struct drm_file *file_priv, @@ -559,7 +561,10 @@ panfrost_submit_job(struct drm_device *dev, struct drm_file *file_priv, if (args->requirements & ~PANFROST_JD_ALLOWED_REQS) return -EINVAL;
- if (!args->head)
- /* If this is a dependency-only job, the job chain head should be NULL,
* otherwise it should be non-NULL.*/- if ((args->head != 0) != !(args->requirements & PANFROST_JD_REQ_DEP_ONLY))
NIT: There's confusion over NULL vs 0 here - the code is correct (args->head is a u64 and not a pointer for a kernel) but the comment makes it seem like it should be a pointer.
We could side-step the mismatch by rewriting as below:
!args->head == !(args->requirements & PANFROST_JD_REQ_DEP_ONLY)
Although I'm not convinced whether that's more readable or not!
return -EINVAL;bo_stride = submit_versions[version].bo_ref_stride; diff --git a/drivers/gpu/drm/panfrost/panfrost_job.c b/drivers/gpu/drm/panfrost/panfrost_job.c index 0367cee8f6df..6d8706d4a096 100644 --- a/drivers/gpu/drm/panfrost/panfrost_job.c +++ b/drivers/gpu/drm/panfrost/panfrost_job.c @@ -192,6 +192,12 @@ static void panfrost_job_hw_submit(struct panfrost_job *job, int js) u64 jc_head = job->jc; int ret;
- if (job->requirements & PANFROST_JD_REQ_DEP_ONLY) {
/* Nothing to execute, signal the fence directly. */dma_fence_signal_locked(job->done_fence);return;- }
It took me a while to convince myself that the reference counting for the PM reference is correct. Before panfrost_job_hw_submit() always returned with an extra reference, but now we have a case which doesn't. AFAICT this is probably fine because we dereference on the path where the hardware has completed the job (which obviously won't happen here). But I'm still a bit uneasy whether the reference counts are always correct.
Steve
panfrost_devfreq_record_busy(&pfdev->pfdevfreq);
ret = pm_runtime_get_sync(pfdev->dev); diff --git a/include/uapi/drm/panfrost_drm.h b/include/uapi/drm/panfrost_drm.h index 5e3f8a344f41..b9df066970f6 100644 --- a/include/uapi/drm/panfrost_drm.h +++ b/include/uapi/drm/panfrost_drm.h @@ -46,6 +46,13 @@ extern "C" { #define DRM_IOCTL_PANFROST_PERFCNT_DUMP DRM_IOW(DRM_COMMAND_BASE + DRM_PANFROST_PERFCNT_DUMP, struct drm_panfrost_perfcnt_dump)
#define PANFROST_JD_REQ_FS (1 << 0)
+/*
- Dependency only job. The job chain head should be set to 0 when this flag
- is set.
- */
+#define PANFROST_JD_REQ_DEP_ONLY (1 << 1)
/**
- struct drm_panfrost_submit - ioctl argument for submitting commands to the 3D
- engine.