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kfd_interrupt.c revision 1.2.6.2 
      1 /*	$NetBSD: kfd_interrupt.c,v 1.2.6.2 2019/06/10 22:07:59 christos 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 1.2.6.2 2019/06/10 22:07:59 christos Exp $");
     47 
     48 #include <linux/slab.h>
     49 #include <linux/device.h>
     50 #include "kfd_priv.h"
     51 
     52 #define KFD_INTERRUPT_RING_SIZE 1024
     53 
     54 static void interrupt_wq(struct work_struct *);
     55 
     56 int kfd_interrupt_init(struct kfd_dev *kfd)
     57 {
     58 	void *interrupt_ring = kmalloc_array(KFD_INTERRUPT_RING_SIZE,
     59 					kfd->device_info->ih_ring_entry_size,
     60 					GFP_KERNEL);
     61 	if (!interrupt_ring)
     62 		return -ENOMEM;
     63 
     64 	kfd->interrupt_ring = interrupt_ring;
     65 	kfd->interrupt_ring_size =
     66 		KFD_INTERRUPT_RING_SIZE * kfd->device_info->ih_ring_entry_size;
     67 	atomic_set(&kfd->interrupt_ring_wptr, 0);
     68 	atomic_set(&kfd->interrupt_ring_rptr, 0);
     69 
     70 	spin_lock_init(&kfd->interrupt_lock);
     71 
     72 	INIT_WORK(&kfd->interrupt_work, interrupt_wq);
     73 
     74 	kfd->interrupts_active = true;
     75 
     76 	/*
     77 	 * After this function returns, the interrupt will be enabled. This
     78 	 * barrier ensures that the interrupt running on a different processor
     79 	 * sees all the above writes.
     80 	 */
     81 	smp_wmb();
     82 
     83 	return 0;
     84 }
     85 
     86 void kfd_interrupt_exit(struct kfd_dev *kfd)
     87 {
     88 	/*
     89 	 * Stop the interrupt handler from writing to the ring and scheduling
     90 	 * workqueue items. The spinlock ensures that any interrupt running
     91 	 * after we have unlocked sees interrupts_active = false.
     92 	 */
     93 	unsigned long flags;
     94 
     95 	spin_lock_irqsave(&kfd->interrupt_lock, flags);
     96 	kfd->interrupts_active = false;
     97 	spin_unlock_irqrestore(&kfd->interrupt_lock, flags);
     98 
     99 	/*
    100 	 * Flush_scheduled_work ensures that there are no outstanding
    101 	 * work-queue items that will access interrupt_ring. New work items
    102 	 * can't be created because we stopped interrupt handling above.
    103 	 */
    104 	flush_scheduled_work();
    105 
    106 	kfree(kfd->interrupt_ring);
    107 }
    108 
    109 /*
    110  * This assumes that it can't be called concurrently with itself
    111  * but only with dequeue_ih_ring_entry.
    112  */
    113 bool enqueue_ih_ring_entry(struct kfd_dev *kfd,	const void *ih_ring_entry)
    114 {
    115 	unsigned int rptr = atomic_read(&kfd->interrupt_ring_rptr);
    116 	unsigned int wptr = atomic_read(&kfd->interrupt_ring_wptr);
    117 
    118 	if ((rptr - wptr) % kfd->interrupt_ring_size ==
    119 					kfd->device_info->ih_ring_entry_size) {
    120 		/* This is very bad, the system is likely to hang. */
    121 		dev_err_ratelimited(kfd_chardev(),
    122 			"Interrupt ring overflow, dropping interrupt.\n");
    123 		return false;
    124 	}
    125 
    126 	memcpy(kfd->interrupt_ring + wptr, ih_ring_entry,
    127 			kfd->device_info->ih_ring_entry_size);
    128 
    129 	wptr = (wptr + kfd->device_info->ih_ring_entry_size) %
    130 			kfd->interrupt_ring_size;
    131 	smp_wmb(); /* Ensure memcpy'd data is visible before wptr update. */
    132 	atomic_set(&kfd->interrupt_ring_wptr, wptr);
    133 
    134 	return true;
    135 }
    136 
    137 /*
    138  * This assumes that it can't be called concurrently with itself
    139  * but only with enqueue_ih_ring_entry.
    140  */
    141 static bool dequeue_ih_ring_entry(struct kfd_dev *kfd, void *ih_ring_entry)
    142 {
    143 	/*
    144 	 * Assume that wait queues have an implicit barrier, i.e. anything that
    145 	 * happened in the ISR before it queued work is visible.
    146 	 */
    147 
    148 	unsigned int wptr = atomic_read(&kfd->interrupt_ring_wptr);
    149 	unsigned int rptr = atomic_read(&kfd->interrupt_ring_rptr);
    150 
    151 	if (rptr == wptr)
    152 		return false;
    153 
    154 	memcpy(ih_ring_entry, kfd->interrupt_ring + rptr,
    155 			kfd->device_info->ih_ring_entry_size);
    156 
    157 	rptr = (rptr + kfd->device_info->ih_ring_entry_size) %
    158 			kfd->interrupt_ring_size;
    159 
    160 	/*
    161 	 * Ensure the rptr write update is not visible until
    162 	 * memcpy has finished reading.
    163 	 */
    164 	smp_mb();
    165 	atomic_set(&kfd->interrupt_ring_rptr, rptr);
    166 
    167 	return true;
    168 }
    169 
    170 static void interrupt_wq(struct work_struct *work)
    171 {
    172 	struct kfd_dev *dev = container_of(work, struct kfd_dev,
    173 						interrupt_work);
    174 
    175 	uint32_t ih_ring_entry[DIV_ROUND_UP(
    176 				dev->device_info->ih_ring_entry_size,
    177 				sizeof(uint32_t))];
    178 
    179 	while (dequeue_ih_ring_entry(dev, ih_ring_entry))
    180 		dev->device_info->event_interrupt_class->interrupt_wq(dev,
    181 								ih_ring_entry);
    182 }
    183 
    184 bool interrupt_is_wanted(struct kfd_dev *dev, const uint32_t *ih_ring_entry)
    185 {
    186 	/* integer and bitwise OR so there is no boolean short-circuiting */
    187 	unsigned wanted = 0;
    188 
    189 	wanted |= dev->device_info->event_interrupt_class->interrupt_isr(dev,
    190 								ih_ring_entry);
    191 
    192 	return wanted != 0;
    193 }
    194