1/*
  2 * Copyright 2014 Advanced Micro Devices, Inc.
  3 *
  4 * Permission is hereby granted, free of charge, to any person obtaining a
  5 * copy of this software and associated documentation files (the "Software"),
  6 * to deal in the Software without restriction, including without limitation
  7 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
  8 * and/or sell copies of the Software, and to permit persons to whom the
  9 * Software is furnished to do so, subject to the following conditions:
 10 *
 11 * The above copyright notice and this permission notice shall be included in
 12 * all copies or substantial portions of the Software.
 13 *
 14 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 15 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 16 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 17 * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
 18 * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
 19 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 20 * OTHER DEALINGS IN THE SOFTWARE.
 21 */
 22
 23/*
 24 * KFD Interrupts.
 25 *
 26 * AMD GPUs deliver interrupts by pushing an interrupt description onto the
 27 * interrupt ring and then sending an interrupt. KGD receives the interrupt
 28 * in ISR and sends us a pointer to each new entry on the interrupt ring.
 29 *
 30 * We generally can't process interrupt-signaled events from ISR, so we call
 31 * out to each interrupt client module (currently only the scheduler) to ask if
 32 * each interrupt is interesting. If they return true, then it requires further
 33 * processing so we copy it to an internal interrupt ring and call each
 34 * interrupt client again from a work-queue.
 35 *
 36 * There's no acknowledgment for the interrupts we use. The hardware simply
 37 * queues a new interrupt each time without waiting.
 38 *
 39 * The fixed-size internal queue means that it's possible for us to lose
 40 * interrupts because we have no back-pressure to the hardware.
 41 */
 42
 43#include <linux/slab.h>
 44#include <linux/device.h>
 45#include "kfd_priv.h"
 46
 47#define KFD_INTERRUPT_RING_SIZE 1024
 48
 49static void interrupt_wq(struct work_struct *);
 50
 51int kfd_interrupt_init(struct kfd_dev *kfd)
 52{
 53	void *interrupt_ring = kmalloc_array(KFD_INTERRUPT_RING_SIZE,
 54					kfd->device_info->ih_ring_entry_size,
 55					GFP_KERNEL);
 56	if (!interrupt_ring)
 57		return -ENOMEM;
 58
 59	kfd->interrupt_ring = interrupt_ring;
 60	kfd->interrupt_ring_size =
 61		KFD_INTERRUPT_RING_SIZE * kfd->device_info->ih_ring_entry_size;
 62	atomic_set(&kfd->interrupt_ring_wptr, 0);
 63	atomic_set(&kfd->interrupt_ring_rptr, 0);
 64
 65	spin_lock_init(&kfd->interrupt_lock);
 66
 67	INIT_WORK(&kfd->interrupt_work, interrupt_wq);
 68
 69	kfd->interrupts_active = true;
 70
 71	/*
 72	 * After this function returns, the interrupt will be enabled. This
 73	 * barrier ensures that the interrupt running on a different processor
 74	 * sees all the above writes.
 75	 */
 76	smp_wmb();
 77
 78	return 0;
 79}
 80
 81void kfd_interrupt_exit(struct kfd_dev *kfd)
 82{
 83	/*
 84	 * Stop the interrupt handler from writing to the ring and scheduling
 85	 * workqueue items. The spinlock ensures that any interrupt running
 86	 * after we have unlocked sees interrupts_active = false.
 87	 */
 88	unsigned long flags;
 89
 90	spin_lock_irqsave(&kfd->interrupt_lock, flags);
 91	kfd->interrupts_active = false;
 92	spin_unlock_irqrestore(&kfd->interrupt_lock, flags);
 93
 94	/*
 95	 * Flush_scheduled_work ensures that there are no outstanding
 96	 * work-queue items that will access interrupt_ring. New work items
 97	 * can't be created because we stopped interrupt handling above.
 98	 */
 99	flush_scheduled_work();
100
101	kfree(kfd->interrupt_ring);
102}
103
104/*
105 * This assumes that it can't be called concurrently with itself
106 * but only with dequeue_ih_ring_entry.
107 */
108bool enqueue_ih_ring_entry(struct kfd_dev *kfd,	const void *ih_ring_entry)
109{
110	unsigned int rptr = atomic_read(&kfd->interrupt_ring_rptr);
111	unsigned int wptr = atomic_read(&kfd->interrupt_ring_wptr);
112
113	if ((rptr - wptr) % kfd->interrupt_ring_size ==
114					kfd->device_info->ih_ring_entry_size) {
115		/* This is very bad, the system is likely to hang. */
116		dev_err_ratelimited(kfd_chardev(),
117			"Interrupt ring overflow, dropping interrupt.\n");
118		return false;
119	}
120
121	memcpy(kfd->interrupt_ring + wptr, ih_ring_entry,
122			kfd->device_info->ih_ring_entry_size);
123
124	wptr = (wptr + kfd->device_info->ih_ring_entry_size) %
125			kfd->interrupt_ring_size;
126	smp_wmb(); /* Ensure memcpy'd data is visible before wptr update. */
127	atomic_set(&kfd->interrupt_ring_wptr, wptr);
128
129	return true;
130}
131
132/*
133 * This assumes that it can't be called concurrently with itself
134 * but only with enqueue_ih_ring_entry.
135 */
136static bool dequeue_ih_ring_entry(struct kfd_dev *kfd, void *ih_ring_entry)
137{
138	/*
139	 * Assume that wait queues have an implicit barrier, i.e. anything that
140	 * happened in the ISR before it queued work is visible.
141	 */
142
143	unsigned int wptr = atomic_read(&kfd->interrupt_ring_wptr);
144	unsigned int rptr = atomic_read(&kfd->interrupt_ring_rptr);
145
146	if (rptr == wptr)
147		return false;
148
149	memcpy(ih_ring_entry, kfd->interrupt_ring + rptr,
150			kfd->device_info->ih_ring_entry_size);
151
152	rptr = (rptr + kfd->device_info->ih_ring_entry_size) %
153			kfd->interrupt_ring_size;
154
155	/*
156	 * Ensure the rptr write update is not visible until
157	 * memcpy has finished reading.
158	 */
159	smp_mb();
160	atomic_set(&kfd->interrupt_ring_rptr, rptr);
161
162	return true;
163}
164
165static void interrupt_wq(struct work_struct *work)
166{
167	struct kfd_dev *dev = container_of(work, struct kfd_dev,
168						interrupt_work);
169
170	uint32_t ih_ring_entry[DIV_ROUND_UP(
171				dev->device_info->ih_ring_entry_size,
172				sizeof(uint32_t))];
173
174	while (dequeue_ih_ring_entry(dev, ih_ring_entry))
175		dev->device_info->event_interrupt_class->interrupt_wq(dev,
176								ih_ring_entry);
177}
178
179bool interrupt_is_wanted(struct kfd_dev *dev, const uint32_t *ih_ring_entry)
180{
181	/* integer and bitwise OR so there is no boolean short-circuiting */
182	unsigned wanted = 0;
183
184	wanted |= dev->device_info->event_interrupt_class->interrupt_isr(dev,
185								ih_ring_entry);
186
187	return wanted != 0;
188}