1/*	$NetBSD: kfd_interrupt.c,v 1.3 2021/12/18 23:44:59 riastradh Exp $	*/
2
3/*
4 * Copyright 2014 Advanced Micro Devices, Inc.
5 *
6 * Permission is hereby granted, free of charge, to any person obtaining a
7 * copy of this software and associated documentation files (the "Software"),
8 * to deal in the Software without restriction, including without limitation
9 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
10 * and/or sell copies of the Software, and to permit persons to whom the
11 * Software is furnished to do so, subject to the following conditions:
12 *
13 * The above copyright notice and this permission notice shall be included in
14 * all copies or substantial portions of the Software.
15 *
16 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
17 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
18 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
19 * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
20 * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
21 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
22 * OTHER DEALINGS IN THE SOFTWARE.
23 */
24
25/*
26 * KFD Interrupts.
27 *
28 * AMD GPUs deliver interrupts by pushing an interrupt description onto the
29 * interrupt ring and then sending an interrupt. KGD receives the interrupt
30 * in ISR and sends us a pointer to each new entry on the interrupt ring.
31 *
32 * We generally can't process interrupt-signaled events from ISR, so we call
33 * out to each interrupt client module (currently only the scheduler) to ask if
34 * each interrupt is interesting. If they return true, then it requires further
35 * processing so we copy it to an internal interrupt ring and call each
36 * interrupt client again from a work-queue.
37 *
38 * There's no acknowledgment for the interrupts we use. The hardware simply
39 * queues a new interrupt each time without waiting.
40 *
41 * The fixed-size internal queue means that it's possible for us to lose
42 * interrupts because we have no back-pressure to the hardware.
43 */
44
45#include <sys/cdefs.h>
46__KERNEL_RCSID(0, "$NetBSD: kfd_interrupt.c,v 1.3 2021/12/18 23:44:59 riastradh Exp $");
47
48#include <linux/slab.h>
49#include <linux/device.h>
50#include <linux/kfifo.h>
51#include "kfd_priv.h"
52
53#define KFD_IH_NUM_ENTRIES 8192
54
55static void interrupt_wq(struct work_struct *);
56
57int kfd_interrupt_init(struct kfd_dev *kfd)
58{
59	int r;
60
61	r = kfifo_alloc(&kfd->ih_fifo,
62		KFD_IH_NUM_ENTRIES * kfd->device_info->ih_ring_entry_size,
63		GFP_KERNEL);
64	if (r) {
65		dev_err(kfd_chardev(), "Failed to allocate IH fifo\n");
66		return r;
67	}
68
69	kfd->ih_wq = alloc_workqueue("KFD IH", WQ_HIGHPRI, 1);
70	if (unlikely(!kfd->ih_wq)) {
71		kfifo_free(&kfd->ih_fifo);
72		dev_err(kfd_chardev(), "Failed to allocate KFD IH workqueue\n");
73		return -ENOMEM;
74	}
75	spin_lock_init(&kfd->interrupt_lock);
76
77	INIT_WORK(&kfd->interrupt_work, interrupt_wq);
78
79	kfd->interrupts_active = true;
80
81	/*
82	 * After this function returns, the interrupt will be enabled. This
83	 * barrier ensures that the interrupt running on a different processor
84	 * sees all the above writes.
85	 */
86	smp_wmb();
87
88	return 0;
89}
90
91void kfd_interrupt_exit(struct kfd_dev *kfd)
92{
93	/*
94	 * Stop the interrupt handler from writing to the ring and scheduling
95	 * workqueue items. The spinlock ensures that any interrupt running
96	 * after we have unlocked sees interrupts_active = false.
97	 */
98	unsigned long flags;
99
100	spin_lock_irqsave(&kfd->interrupt_lock, flags);
101	kfd->interrupts_active = false;
102	spin_unlock_irqrestore(&kfd->interrupt_lock, flags);
103
104	/*
105	 * flush_work ensures that there are no outstanding
106	 * work-queue items that will access interrupt_ring. New work items
107	 * can't be created because we stopped interrupt handling above.
108	 */
109	flush_workqueue(kfd->ih_wq);
110
111	kfifo_free(&kfd->ih_fifo);
112}
113
114/*
115 * Assumption: single reader/writer. This function is not re-entrant
116 */
117bool enqueue_ih_ring_entry(struct kfd_dev *kfd,	const void *ih_ring_entry)
118{
119	int count;
120
121	count = kfifo_in(&kfd->ih_fifo, ih_ring_entry,
122				kfd->device_info->ih_ring_entry_size);
123	if (count != kfd->device_info->ih_ring_entry_size) {
124		dev_err_ratelimited(kfd_chardev(),
125			"Interrupt ring overflow, dropping interrupt %d\n",
126			count);
127		return false;
128	}
129
130	return true;
131}
132
133/*
134 * Assumption: single reader/writer. This function is not re-entrant
135 */
136static bool dequeue_ih_ring_entry(struct kfd_dev *kfd, void *ih_ring_entry)
137{
138	int count;
139
140	count = kfifo_out(&kfd->ih_fifo, ih_ring_entry,
141				kfd->device_info->ih_ring_entry_size);
142
143	WARN_ON(count && count != kfd->device_info->ih_ring_entry_size);
144
145	return count == kfd->device_info->ih_ring_entry_size;
146}
147
148static void interrupt_wq(struct work_struct *work)
149{
150	struct kfd_dev *dev = container_of(work, struct kfd_dev,
151						interrupt_work);
152	uint32_t ih_ring_entry[KFD_MAX_RING_ENTRY_SIZE];
153
154	if (dev->device_info->ih_ring_entry_size > sizeof(ih_ring_entry)) {
155		dev_err_once(kfd_chardev(), "Ring entry too small\n");
156		return;
157	}
158
159	while (dequeue_ih_ring_entry(dev, ih_ring_entry))
160		dev->device_info->event_interrupt_class->interrupt_wq(dev,
161								ih_ring_entry);
162}
163
164bool interrupt_is_wanted(struct kfd_dev *dev,
165			const uint32_t *ih_ring_entry,
166			uint32_t *patched_ihre, bool *flag)
167{
168	/* integer and bitwise OR so there is no boolean short-circuiting */
169	unsigned int wanted = 0;
170
171	wanted |= dev->device_info->event_interrupt_class->interrupt_isr(dev,
172					 ih_ring_entry, patched_ihre, flag);
173
174	return wanted != 0;
175}
176