1/*
2 * SPDX-License-Identifier: MIT
3 *
4 * Copyright �� 2014-2016 Intel Corporation
5 */
6
7#include <linux/dma-fence-array.h>
8
9#include "gt/intel_engine.h"
10
11#include "i915_gem_ioctls.h"
12#include "i915_gem_object.h"
13
14static __always_inline u32 __busy_read_flag(u16 id)
15{
16	if (id == (u16)I915_ENGINE_CLASS_INVALID)
17		return 0xffff0000u;
18
19	GEM_BUG_ON(id >= 16);
20	return 0x10000u << id;
21}
22
23static __always_inline u32 __busy_write_id(u16 id)
24{
25	/*
26	 * The uABI guarantees an active writer is also amongst the read
27	 * engines. This would be true if we accessed the activity tracking
28	 * under the lock, but as we perform the lookup of the object and
29	 * its activity locklessly we can not guarantee that the last_write
30	 * being active implies that we have set the same engine flag from
31	 * last_read - hence we always set both read and write busy for
32	 * last_write.
33	 */
34	if (id == (u16)I915_ENGINE_CLASS_INVALID)
35		return 0xffffffffu;
36
37	return (id + 1) | __busy_read_flag(id);
38}
39
40static __always_inline unsigned int
41__busy_set_if_active(struct dma_fence *fence, u32 (*flag)(u16 id))
42{
43	const struct i915_request *rq;
44
45	/*
46	 * We have to check the current hw status of the fence as the uABI
47	 * guarantees forward progress. We could rely on the idle worker
48	 * to eventually flush us, but to minimise latency just ask the
49	 * hardware.
50	 *
51	 * Note we only report on the status of native fences and we currently
52	 * have two native fences:
53	 *
54	 * 1. A composite fence (dma_fence_array) constructed of i915 requests
55	 * created during a parallel submission. In this case we deconstruct the
56	 * composite fence into individual i915 requests and check the status of
57	 * each request.
58	 *
59	 * 2. A single i915 request.
60	 */
61	if (dma_fence_is_array(fence)) {
62		struct dma_fence_array *array = to_dma_fence_array(fence);
63		struct dma_fence **child = array->fences;
64		unsigned int nchild = array->num_fences;
65
66		do {
67			struct dma_fence *current_fence = *child++;
68
69			/* Not an i915 fence, can't be busy per above */
70			if (!dma_fence_is_i915(current_fence) ||
71			    !test_bit(I915_FENCE_FLAG_COMPOSITE,
72				      &current_fence->flags)) {
73				return 0;
74			}
75
76			rq = to_request(current_fence);
77			if (!i915_request_completed(rq))
78				return flag(rq->engine->uabi_class);
79		} while (--nchild);
80
81		/* All requests in array complete, not busy */
82		return 0;
83	} else {
84		if (!dma_fence_is_i915(fence))
85			return 0;
86
87		rq = to_request(fence);
88		if (i915_request_completed(rq))
89			return 0;
90
91		/* Beware type-expansion follies! */
92		BUILD_BUG_ON(!typecheck(u16, rq->engine->uabi_class));
93		return flag(rq->engine->uabi_class);
94	}
95}
96
97static __always_inline unsigned int
98busy_check_reader(struct dma_fence *fence)
99{
100	return __busy_set_if_active(fence, __busy_read_flag);
101}
102
103static __always_inline unsigned int
104busy_check_writer(struct dma_fence *fence)
105{
106	if (!fence)
107		return 0;
108
109	return __busy_set_if_active(fence, __busy_write_id);
110}
111
112int
113i915_gem_busy_ioctl(struct drm_device *dev, void *data,
114		    struct drm_file *file)
115{
116	struct drm_i915_gem_busy *args = data;
117	struct drm_i915_gem_object *obj;
118	struct dma_resv_iter cursor;
119	struct dma_fence *fence;
120	int err;
121
122	err = -ENOENT;
123	rcu_read_lock();
124	obj = i915_gem_object_lookup_rcu(file, args->handle);
125	if (!obj)
126		goto out;
127
128	/*
129	 * A discrepancy here is that we do not report the status of
130	 * non-i915 fences, i.e. even though we may report the object as idle,
131	 * a call to set-domain may still stall waiting for foreign rendering.
132	 * This also means that wait-ioctl may report an object as busy,
133	 * where busy-ioctl considers it idle.
134	 *
135	 * We trade the ability to warn of foreign fences to report on which
136	 * i915 engines are active for the object.
137	 *
138	 * Alternatively, we can trade that extra information on read/write
139	 * activity with
140	 *	args->busy =
141	 *		!dma_resv_test_signaled(obj->resv, DMA_RESV_USAGE_READ);
142	 * to report the overall busyness. This is what the wait-ioctl does.
143	 *
144	 */
145	args->busy = 0;
146	dma_resv_iter_begin(&cursor, obj->base.resv, DMA_RESV_USAGE_READ);
147	dma_resv_for_each_fence_unlocked(&cursor, fence) {
148		if (dma_resv_iter_is_restarted(&cursor))
149			args->busy = 0;
150
151		if (dma_resv_iter_usage(&cursor) <= DMA_RESV_USAGE_WRITE)
152			/* Translate the write fences to the READ *and* WRITE engine */
153			args->busy |= busy_check_writer(fence);
154		else
155			/* Translate read fences to READ set of engines */
156			args->busy |= busy_check_reader(fence);
157	}
158	dma_resv_iter_end(&cursor);
159
160	err = 0;
161out:
162	rcu_read_unlock();
163	return err;
164}
165