dma-buf/sw_sync: Add fence deadline support

This consists of simply storing the most recent deadline, and adding an
ioctl to retrieve the deadline.  This can be used in conjunction with
the SET_DEADLINE ioctl on a fence fd for testing.  Ie. create various
sw_sync fences, merge them into a fence-array, set deadline on the
fence-array and confirm that it is propagated properly to each fence.

v2: Switch UABI to express deadline as u64
v3: More verbose UAPI docs, show how to convert from timespec
v4: Better comments, track the soonest deadline, as a normal fence
    implementation would, return an error if no deadline set.

Signed-off-by: Rob Clark <robdclark@chromium.org>
Reviewed-by: Christian König <christian.koenig@amd.com>
Acked-by: Pekka Paalanen <pekka.paalanen@collabora.com>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20230823215458.203366-4-robdclark@gmail.com

Author: robclark

drivers/dma-buf/sw_sync.c

@@ -52,12 +52,33 @@ struct sw_sync_create_fence_data {
 	__s32	fence; /* fd of new fence */
 };
 
+/**
+ * struct sw_sync_get_deadline - get the deadline hint of a sw_sync fence
+ * @deadline_ns: absolute time of the deadline
+ * @pad:	must be zero
+ * @fence_fd:	the sw_sync fence fd (in)
+ *
+ * Return the earliest deadline set on the fence.  The timebase for the
+ * deadline is CLOCK_MONOTONIC (same as vblank).  If there is no deadline
+ * set on the fence, this ioctl will return -ENOENT.
+ */
+struct sw_sync_get_deadline {
+	__u64	deadline_ns;
+	__u32	pad;
+	__s32	fence_fd;
+};
+
 #define SW_SYNC_IOC_MAGIC	'W'
 
 #define SW_SYNC_IOC_CREATE_FENCE	_IOWR(SW_SYNC_IOC_MAGIC, 0,\
 		struct sw_sync_create_fence_data)
 
 #define SW_SYNC_IOC_INC			_IOW(SW_SYNC_IOC_MAGIC, 1, __u32)
+#define SW_SYNC_GET_DEADLINE		_IOWR(SW_SYNC_IOC_MAGIC, 2, \
+		struct sw_sync_get_deadline)
+
+
+#define SW_SYNC_HAS_DEADLINE_BIT	DMA_FENCE_FLAG_USER_BITS
 
 static const struct dma_fence_ops timeline_fence_ops;
 
@@ -171,6 +192,22 @@ static void timeline_fence_timeline_value_str(struct dma_fence *fence,
 	snprintf(str, size, "%d", parent->value);
 }
 
+static void timeline_fence_set_deadline(struct dma_fence *fence, ktime_t deadline)
+{
+	struct sync_pt *pt = dma_fence_to_sync_pt(fence);
+	unsigned long flags;
+
+	spin_lock_irqsave(fence->lock, flags);
+	if (test_bit(SW_SYNC_HAS_DEADLINE_BIT, &fence->flags)) {
+		if (ktime_before(deadline, pt->deadline))
+			pt->deadline = deadline;
+	} else {
+		pt->deadline = deadline;
+		__set_bit(SW_SYNC_HAS_DEADLINE_BIT, &fence->flags);
+	}
+	spin_unlock_irqrestore(fence->lock, flags);
+}
+
 static const struct dma_fence_ops timeline_fence_ops = {
 	.get_driver_name = timeline_fence_get_driver_name,
 	.get_timeline_name = timeline_fence_get_timeline_name,
@@ -179,6 +216,7 @@ static const struct dma_fence_ops timeline_fence_ops = {
 	.release = timeline_fence_release,
 	.fence_value_str = timeline_fence_value_str,
 	.timeline_value_str = timeline_fence_timeline_value_str,
+	.set_deadline = timeline_fence_set_deadline,
 };
 
 /**
@@ -387,6 +425,47 @@ static long sw_sync_ioctl_inc(struct sync_timeline *obj, unsigned long arg)
 	return 0;
 }
 
+static int sw_sync_ioctl_get_deadline(struct sync_timeline *obj, unsigned long arg)
+{
+	struct sw_sync_get_deadline data;
+	struct dma_fence *fence;
+	unsigned long flags;
+	struct sync_pt *pt;
+	int ret = 0;
+
+	if (copy_from_user(&data, (void __user *)arg, sizeof(data)))
+		return -EFAULT;
+
+	if (data.deadline_ns || data.pad)
+		return -EINVAL;
+
+	fence = sync_file_get_fence(data.fence_fd);
+	if (!fence)
+		return -EINVAL;
+
+	pt = dma_fence_to_sync_pt(fence);
+	if (!pt)
+		return -EINVAL;
+
+	spin_lock_irqsave(fence->lock, flags);
+	if (test_bit(SW_SYNC_HAS_DEADLINE_BIT, &fence->flags)) {
+		data.deadline_ns = ktime_to_ns(pt->deadline);
+	} else {
+		ret = -ENOENT;
+	}
+	spin_unlock_irqrestore(fence->lock, flags);
+
+	dma_fence_put(fence);
+
+	if (ret)
+		return ret;
+
+	if (copy_to_user((void __user *)arg, &data, sizeof(data)))
+		return -EFAULT;
+
+	return 0;
+}
+
 static long sw_sync_ioctl(struct file *file, unsigned int cmd,
 			  unsigned long arg)
 {
@@ -399,6 +478,9 @@ static long sw_sync_ioctl(struct file *file, unsigned int cmd,
 	case SW_SYNC_IOC_INC:
 		return sw_sync_ioctl_inc(obj, arg);
 
+	case SW_SYNC_GET_DEADLINE:
+		return sw_sync_ioctl_get_deadline(obj, arg);
+
 	default:
 		return -ENOTTY;
 	}

drivers/dma-buf/sync_debug.h

@@ -55,11 +55,13 @@ static inline struct sync_timeline *dma_fence_parent(struct dma_fence *fence)
  * @base: base fence object
  * @link: link on the sync timeline's list
  * @node: node in the sync timeline's tree
+ * @deadline: the earliest fence deadline hint
  */
 struct sync_pt {
 	struct dma_fence base;
 	struct list_head link;
 	struct rb_node node;
+	ktime_t deadline;
 };
 
 extern const struct file_operations sw_sync_debugfs_fops;