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}