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 49 static void interrupt_wq(struct work_struct *); 50 51 int 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 81 void 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 */ 108 bool 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 */ 136 static 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 } 164 165 static 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 } 178 179 bool 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 } 189