drm/syncobj: add sync obj wait interface. (v8)

This interface will allow sync object to be used to back
Vulkan fences. This API is pretty much the vulkan fence waiting
API, and I've ported the code from amdgpu.

v2: accept relative timeout, pass remaining time back
to userspace.
v3: return to absolute timeouts.
v4: absolute zero = poll,
    rewrite any/all code to have same operation for arrays
    return -EINVAL for 0 fences.
v4.1: fixup fences allocation check, use u64_to_user_ptr
v5: move to sec/nsec, and use timespec64 for calcs.
v6: use -ETIME and drop the out status flag. (-ETIME
is suggested by ickle, I can feel a shed painting)
v7: talked to Daniel/Arnd, use ktime and ns everywhere.
v8: be more careful in the timeout calculations
    use uint32_t for counter variables so we don't overflow
    graciously handle -ENOINT being returned from dma_fence_wait_timeout

Signed-off-by: Dave Airlie <airlied@redhat.com>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Acked-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/drm_internal.h

@@ -167,3 +167,5 @@ int drm_syncobj_handle_to_fd_ioctl(struct drm_device *dev, void *data,
 				   struct drm_file *file_private);
 int drm_syncobj_fd_to_handle_ioctl(struct drm_device *dev, void *data,
 				   struct drm_file *file_private);
+int drm_syncobj_wait_ioctl(struct drm_device *dev, void *data,
+			   struct drm_file *file_private);

drivers/gpu/drm/drm_ioctl.c

@@ -657,6 +657,8 @@ static const struct drm_ioctl_desc drm_ioctls[] = {
 		      DRM_UNLOCKED|DRM_RENDER_ALLOW),
 	DRM_IOCTL_DEF(DRM_IOCTL_SYNCOBJ_FD_TO_HANDLE, drm_syncobj_fd_to_handle_ioctl,
 		      DRM_UNLOCKED|DRM_RENDER_ALLOW),
+	DRM_IOCTL_DEF(DRM_IOCTL_SYNCOBJ_WAIT, drm_syncobj_wait_ioctl,
+		      DRM_UNLOCKED|DRM_RENDER_ALLOW),
 };
 
 #define DRM_CORE_IOCTL_COUNT	ARRAY_SIZE( drm_ioctls )

drivers/gpu/drm/drm_syncobj.c

@@ -1,5 +1,7 @@
 /*
  * Copyright 2017 Red Hat
+ * Parts ported from amdgpu (fence wait code).
+ * Copyright 2016 Advanced Micro Devices, Inc.
  *
  * Permission is hereby granted, free of charge, to any person obtaining a
  * copy of this software and associated documentation files (the "Software"),
@@ -31,6 +33,9 @@
  * that contain an optional fence. The fence can be updated with a new
  * fence, or be NULL.
  *
+ * syncobj's can be waited upon, where it will wait for the underlying
+ * fence.
+ *
  * syncobj's can be export to fd's and back, these fd's are opaque and
  * have no other use case, except passing the syncobj between processes.
  *
@@ -447,3 +452,140 @@ drm_syncobj_fd_to_handle_ioctl(struct drm_device *dev, void *data,
 	return drm_syncobj_fd_to_handle(file_private, args->fd,
 					&args->handle);
 }
+
+/**
+ * drm_timeout_abs_to_jiffies - calculate jiffies timeout from absolute value
+ *
+ * @timeout_nsec: timeout nsec component in ns, 0 for poll
+ *
+ * Calculate the timeout in jiffies from an absolute time in sec/nsec.
+ */
+static signed long drm_timeout_abs_to_jiffies(int64_t timeout_nsec)
+{
+	ktime_t abs_timeout, now;
+	u64 timeout_ns, timeout_jiffies64;
+
+	/* make 0 timeout means poll - absolute 0 doesn't seem valid */
+	if (timeout_nsec == 0)
+		return 0;
+
+	abs_timeout = ns_to_ktime(timeout_nsec);
+	now = ktime_get();
+
+	if (!ktime_after(abs_timeout, now))
+		return 0;
+
+	timeout_ns = ktime_to_ns(ktime_sub(abs_timeout, now));
+
+	timeout_jiffies64 = nsecs_to_jiffies64(timeout_ns);
+	/*  clamp timeout to avoid infinite timeout */
+	if (timeout_jiffies64 >= MAX_SCHEDULE_TIMEOUT - 1)
+		return MAX_SCHEDULE_TIMEOUT - 1;
+
+	return timeout_jiffies64 + 1;
+}
+
+static int drm_syncobj_wait_fences(struct drm_device *dev,
+				   struct drm_file *file_private,
+				   struct drm_syncobj_wait *wait,
+				   struct dma_fence **fences)
+{
+	signed long timeout = drm_timeout_abs_to_jiffies(wait->timeout_nsec);
+	signed long ret = 0;
+	uint32_t first = ~0;
+
+	if (wait->flags & DRM_SYNCOBJ_WAIT_FLAGS_WAIT_ALL) {
+		uint32_t i;
+		for (i = 0; i < wait->count_handles; i++) {
+			ret = dma_fence_wait_timeout(fences[i], true, timeout);
+
+			/* Various dma_fence wait callbacks will return
+			 * ENOENT to indicate that the fence has already
+			 * been signaled.  We need to sanitize this to 0 so
+			 * we don't return early and the client doesn't see
+			 * an unexpected error.
+			 */
+			if (ret == -ENOENT)
+				ret = 0;
+
+			if (ret < 0)
+				return ret;
+			if (ret == 0)
+				break;
+			timeout = ret;
+		}
+		first = 0;
+	} else {
+		ret = dma_fence_wait_any_timeout(fences,
+						 wait->count_handles,
+						 true, timeout,
+						 &first);
+	}
+
+	if (ret < 0)
+		return ret;
+
+	wait->first_signaled = first;
+	if (ret == 0)
+		return -ETIME;
+	return 0;
+}
+
+int
+drm_syncobj_wait_ioctl(struct drm_device *dev, void *data,
+		       struct drm_file *file_private)
+{
+	struct drm_syncobj_wait *args = data;
+	uint32_t *handles;
+	struct dma_fence **fences;
+	int ret = 0;
+	uint32_t i;
+
+	if (!drm_core_check_feature(dev, DRIVER_SYNCOBJ))
+		return -ENODEV;
+
+	if (args->flags != 0 && args->flags != DRM_SYNCOBJ_WAIT_FLAGS_WAIT_ALL)
+		return -EINVAL;
+
+	if (args->count_handles == 0)
+		return -EINVAL;
+
+	/* Get the handles from userspace */
+	handles = kmalloc_array(args->count_handles, sizeof(uint32_t),
+				GFP_KERNEL);
+	if (handles == NULL)
+		return -ENOMEM;
+
+	if (copy_from_user(handles,
+			   u64_to_user_ptr(args->handles),
+			   sizeof(uint32_t) * args->count_handles)) {
+		ret = -EFAULT;
+		goto err_free_handles;
+	}
+
+	fences = kcalloc(args->count_handles,
+			 sizeof(struct dma_fence *), GFP_KERNEL);
+	if (!fences) {
+		ret = -ENOMEM;
+		goto err_free_handles;
+	}
+
+	for (i = 0; i < args->count_handles; i++) {
+		ret = drm_syncobj_find_fence(file_private, handles[i],
+					     &fences[i]);
+		if (ret)
+			goto err_free_fence_array;
+	}
+
+	ret = drm_syncobj_wait_fences(dev, file_private,
+				      args, fences);
+
+err_free_fence_array:
+	for (i = 0; i < args->count_handles; i++)
+		dma_fence_put(fences[i]);
+	kfree(fences);
+err_free_handles:
+	kfree(handles);
+
+	return ret;
+}

include/uapi/drm/drm.h

@@ -718,6 +718,17 @@ struct drm_syncobj_handle {
 	__u32 pad;
 };
 
+#define DRM_SYNCOBJ_WAIT_FLAGS_WAIT_ALL (1 << 0)
+struct drm_syncobj_wait {
+	__u64 handles;
+	/* absolute timeout */
+	__s64 timeout_nsec;
+	__u32 count_handles;
+	__u32 flags;
+	__u32 first_signaled; /* only valid when not waiting all */
+	__u32 pad;
+};
+
 #if defined(__cplusplus)
 }
 #endif
@@ -840,6 +851,7 @@ extern "C" {
 #define DRM_IOCTL_SYNCOBJ_DESTROY	DRM_IOWR(0xC0, struct drm_syncobj_destroy)
 #define DRM_IOCTL_SYNCOBJ_HANDLE_TO_FD	DRM_IOWR(0xC1, struct drm_syncobj_handle)
 #define DRM_IOCTL_SYNCOBJ_FD_TO_HANDLE	DRM_IOWR(0xC2, struct drm_syncobj_handle)
+#define DRM_IOCTL_SYNCOBJ_WAIT		DRM_IOWR(0xC3, struct drm_syncobj_wait)
 
 /**
  * Device specific ioctls should only be in their respective headers