[PATCH v4 3/7] drm/panfrost: Add BO access flags to relax dependencies between jobs

[Boris Brezillon]

Jobs reading from the same BO should not be serialized. Add access
flags so we can relax the implicit dependencies in that case. We force
exclusive access for now to keep the behavior unchanged, but a new
SUBMIT ioctl taking explicit access flags will be introduced.

Signed-off-by: Boris Brezillon <boris.brezillon at collabora.com>
Reviewed-by: Steven Price <steven.price at arm.com>
---
 drivers/gpu/drm/panfrost/panfrost_drv.c |  9 +++++++++
 drivers/gpu/drm/panfrost/panfrost_job.c | 23 +++++++++++++++++++----
 drivers/gpu/drm/panfrost/panfrost_job.h |  1 +
 include/uapi/drm/panfrost_drm.h         |  3 +++
 4 files changed, 32 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/panfrost/panfrost_drv.c b/drivers/gpu/drm/panfrost/panfrost_drv.c
index 9bbc9e78cc85..b6b5997c9366 100644
--- a/drivers/gpu/drm/panfrost/panfrost_drv.c
+++ b/drivers/gpu/drm/panfrost/panfrost_drv.c
@@ -164,6 +164,15 @@ panfrost_lookup_bos(struct drm_device *dev,
 	if (!job->bo_count)
 		return 0;
 
+	job->bo_flags = kvmalloc_array(job->bo_count,
+				       sizeof(*job->bo_flags),
+				       GFP_KERNEL | __GFP_ZERO);
+	if (!job->bo_flags)
+		return -ENOMEM;
+
+	for (i = 0; i < job->bo_count; i++)
+		job->bo_flags[i] = PANFROST_BO_REF_EXCLUSIVE;
+
 	ret = drm_gem_objects_lookup(file_priv,
 				     (void __user *)(uintptr_t)args->bo_handles,
 				     job->bo_count, &job->bos);
diff --git a/drivers/gpu/drm/panfrost/panfrost_job.c b/drivers/gpu/drm/panfrost/panfrost_job.c
index fdc1bd7ecf12..152245b122be 100644
--- a/drivers/gpu/drm/panfrost/panfrost_job.c
+++ b/drivers/gpu/drm/panfrost/panfrost_job.c
@@ -245,8 +245,16 @@ static int panfrost_acquire_object_fences(struct panfrost_job *job)
 	int i, ret;
 
 	for (i = 0; i < job->bo_count; i++) {
-		/* panfrost always uses write mode in its current uapi */
-		ret = drm_gem_fence_array_add_implicit(&job->deps, job->bos[i], true);
+		bool exclusive = job->bo_flags[i] & PANFROST_BO_REF_EXCLUSIVE;
+
+		if (!exclusive) {
+			ret = dma_resv_reserve_shared(job->bos[i]->resv, 1);
+			if (ret)
+				return ret;
+		}
+
+		ret = drm_gem_fence_array_add_implicit(&job->deps, job->bos[i],
+						       exclusive);
 		if (ret)
 			return ret;
 	}
@@ -258,8 +266,14 @@ static void panfrost_attach_object_fences(struct panfrost_job *job)
 {
 	int i;
 
-	for (i = 0; i < job->bo_count; i++)
-		dma_resv_add_excl_fence(job->bos[i]->resv, job->render_done_fence);
+	for (i = 0; i < job->bo_count; i++) {
+		struct dma_resv *robj = job->bos[i]->resv;
+
+		if (job->bo_flags[i] & PANFROST_BO_REF_EXCLUSIVE)
+			dma_resv_add_excl_fence(robj, job->render_done_fence);
+		else
+			dma_resv_add_shared_fence(robj, job->render_done_fence);
+	}
 }
 
 int panfrost_job_push(struct panfrost_job *job)
@@ -340,6 +354,7 @@ static void panfrost_job_cleanup(struct kref *ref)
 		kvfree(job->bos);
 	}
 
+	kvfree(job->bo_flags);
 	kfree(job);
 }
 
diff --git a/drivers/gpu/drm/panfrost/panfrost_job.h b/drivers/gpu/drm/panfrost/panfrost_job.h
index 82306a03b57e..1cbc3621b663 100644
--- a/drivers/gpu/drm/panfrost/panfrost_job.h
+++ b/drivers/gpu/drm/panfrost/panfrost_job.h
@@ -32,6 +32,7 @@ struct panfrost_job {
 
 	struct panfrost_gem_mapping **mappings;
 	struct drm_gem_object **bos;
+	u32 *bo_flags;
 	u32 bo_count;
 
 	/* Fence to be signaled by drm-sched once its done with the job */
diff --git a/include/uapi/drm/panfrost_drm.h b/include/uapi/drm/panfrost_drm.h
index 061e700dd06c..3723c9d231b5 100644
--- a/include/uapi/drm/panfrost_drm.h
+++ b/include/uapi/drm/panfrost_drm.h
@@ -224,6 +224,9 @@ struct drm_panfrost_madvise {
 	__u32 retained;       /* out, whether backing store still exists */
 };
 
+/* Exclusive (AKA write) access to the BO */
+#define PANFROST_BO_REF_EXCLUSIVE	0x1
+
 #if defined(__cplusplus)
 }
 #endif
-- 
2.31.1