1// SPDX-License-Identifier: GPL-2.0 OR MIT
2/*
3 * Copyright 2014-2022 Advanced Micro Devices, Inc.
4 *
5 * Permission is hereby granted, free of charge, to any person obtaining a
6 * copy of this software and associated documentation files (the "Software"),
7 * to deal in the Software without restriction, including without limitation
8 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
9 * and/or sell copies of the Software, and to permit persons to whom the
10 * Software is furnished to do so, subject to the following conditions:
11 *
12 * The above copyright notice and this permission notice shall be included in
13 * all copies or substantial portions of the Software.
14 *
15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
16 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
17 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
18 * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
19 * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
20 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
21 * OTHER DEALINGS IN THE SOFTWARE.
22 */
23
24/*
25 * KFD Interrupts.
26 *
27 * AMD GPUs deliver interrupts by pushing an interrupt description onto the
28 * interrupt ring and then sending an interrupt. KGD receives the interrupt
29 * in ISR and sends us a pointer to each new entry on the interrupt ring.
30 *
31 * We generally can't process interrupt-signaled events from ISR, so we call
32 * out to each interrupt client module (currently only the scheduler) to ask if
33 * each interrupt is interesting. If they return true, then it requires further
34 * processing so we copy it to an internal interrupt ring and call each
35 * interrupt client again from a work-queue.
36 *
37 * There's no acknowledgment for the interrupts we use. The hardware simply
38 * queues a new interrupt each time without waiting.
39 *
40 * The fixed-size internal queue means that it's possible for us to lose
41 * interrupts because we have no back-pressure to the hardware.
42 */
43
44#include <linux/slab.h>
45#include <linux/device.h>
46#include <linux/kfifo.h>
47#include "kfd_priv.h"
48
49#define KFD_IH_NUM_ENTRIES 8192
50
51static void interrupt_wq(struct work_struct *);
52
53int kfd_interrupt_init(struct kfd_node *node)
54{
55	int r;
56
57	r = kfifo_alloc(&node->ih_fifo,
58		KFD_IH_NUM_ENTRIES * node->kfd->device_info.ih_ring_entry_size,
59		GFP_KERNEL);
60	if (r) {
61		dev_err(node->adev->dev, "Failed to allocate IH fifo\n");
62		return r;
63	}
64
65	node->ih_wq = alloc_workqueue("KFD IH", WQ_HIGHPRI, 1);
66	if (unlikely(!node->ih_wq)) {
67		kfifo_free(&node->ih_fifo);
68		dev_err(node->adev->dev, "Failed to allocate KFD IH workqueue\n");
69		return -ENOMEM;
70	}
71	spin_lock_init(&node->interrupt_lock);
72
73	INIT_WORK(&node->interrupt_work, interrupt_wq);
74
75	node->interrupts_active = true;
76
77	/*
78	 * After this function returns, the interrupt will be enabled. This
79	 * barrier ensures that the interrupt running on a different processor
80	 * sees all the above writes.
81	 */
82	smp_wmb();
83
84	return 0;
85}
86
87void kfd_interrupt_exit(struct kfd_node *node)
88{
89	/*
90	 * Stop the interrupt handler from writing to the ring and scheduling
91	 * workqueue items. The spinlock ensures that any interrupt running
92	 * after we have unlocked sees interrupts_active = false.
93	 */
94	unsigned long flags;
95
96	spin_lock_irqsave(&node->interrupt_lock, flags);
97	node->interrupts_active = false;
98	spin_unlock_irqrestore(&node->interrupt_lock, flags);
99
100	/*
101	 * flush_work ensures that there are no outstanding
102	 * work-queue items that will access interrupt_ring. New work items
103	 * can't be created because we stopped interrupt handling above.
104	 */
105	flush_workqueue(node->ih_wq);
106
107	kfifo_free(&node->ih_fifo);
108}
109
110/*
111 * Assumption: single reader/writer. This function is not re-entrant
112 */
113bool enqueue_ih_ring_entry(struct kfd_node *node, const void *ih_ring_entry)
114{
115	int count;
116
117	count = kfifo_in(&node->ih_fifo, ih_ring_entry,
118				node->kfd->device_info.ih_ring_entry_size);
119	if (count != node->kfd->device_info.ih_ring_entry_size) {
120		dev_dbg_ratelimited(node->adev->dev,
121			"Interrupt ring overflow, dropping interrupt %d\n",
122			count);
123		return false;
124	}
125
126	return true;
127}
128
129/*
130 * Assumption: single reader/writer. This function is not re-entrant
131 */
132static bool dequeue_ih_ring_entry(struct kfd_node *node, void *ih_ring_entry)
133{
134	int count;
135
136	count = kfifo_out(&node->ih_fifo, ih_ring_entry,
137				node->kfd->device_info.ih_ring_entry_size);
138
139	WARN_ON(count && count != node->kfd->device_info.ih_ring_entry_size);
140
141	return count == node->kfd->device_info.ih_ring_entry_size;
142}
143
144static void interrupt_wq(struct work_struct *work)
145{
146	struct kfd_node *dev = container_of(work, struct kfd_node,
147						interrupt_work);
148	uint32_t ih_ring_entry[KFD_MAX_RING_ENTRY_SIZE];
149	unsigned long start_jiffies = jiffies;
150
151	if (dev->kfd->device_info.ih_ring_entry_size > sizeof(ih_ring_entry)) {
152		dev_err_once(dev->adev->dev, "Ring entry too small\n");
153		return;
154	}
155
156	while (dequeue_ih_ring_entry(dev, ih_ring_entry)) {
157		dev->kfd->device_info.event_interrupt_class->interrupt_wq(dev,
158								ih_ring_entry);
159		if (time_is_before_jiffies(start_jiffies + HZ)) {
160			/* If we spent more than a second processing signals,
161			 * reschedule the worker to avoid soft-lockup warnings
162			 */
163			queue_work(dev->ih_wq, &dev->interrupt_work);
164			break;
165		}
166	}
167}
168
169bool interrupt_is_wanted(struct kfd_node *dev,
170			const uint32_t *ih_ring_entry,
171			uint32_t *patched_ihre, bool *flag)
172{
173	/* integer and bitwise OR so there is no boolean short-circuiting */
174	unsigned int wanted = 0;
175
176	wanted |= dev->kfd->device_info.event_interrupt_class->interrupt_isr(dev,
177					 ih_ring_entry, patched_ihre, flag);
178
179	return wanted != 0;
180}
181