// SPDX-License-Identifier: GPL-2.0 OR MIT
/*
 * Copyright 2014-2022 Advanced Micro Devices, Inc.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
 * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 * OTHER DEALINGS IN THE SOFTWARE.
 */

/*
 * KFD Interrupts.
 *
 * AMD GPUs deliver interrupts by pushing an interrupt description onto the
 * interrupt ring and then sending an interrupt. KGD receives the interrupt
 * in ISR and sends us a pointer to each new entry on the interrupt ring.
 *
 * We generally can't process interrupt-signaled events from ISR, so we call
 * out to each interrupt client module (currently only the scheduler) to ask if
 * each interrupt is interesting. If they return true, then it requires further
 * processing so we copy it to an internal interrupt ring and call each
 * interrupt client again from a work-queue.
 *
 * There's no acknowledgment for the interrupts we use. The hardware simply
 * queues a new interrupt each time without waiting.
 *
 * The fixed-size internal queue means that it's possible for us to lose
 * interrupts because we have no back-pressure to the hardware.
 */

#include <linux/slab.h>
#include <linux/device.h>
#include <linux/kfifo.h>
#include "kfd_priv.h"

#define KFD_IH_NUM_ENTRIES 16384

static void interrupt_wq(struct work_struct *);

int kfd_interrupt_init(struct kfd_node *node)
{
        int r;

        r = kfifo_alloc(&node->ih_fifo,
                KFD_IH_NUM_ENTRIES * node->kfd->device_info.ih_ring_entry_size,
                GFP_KERNEL);
        if (r) {
                dev_err(node->adev->dev, "Failed to allocate IH fifo\n");
                return r;
        }

        if (!node->kfd->ih_wq) {
                node->kfd->ih_wq = alloc_workqueue("KFD IH", WQ_HIGHPRI | WQ_UNBOUND,
                                                   node->kfd->num_nodes);
                if (unlikely(!node->kfd->ih_wq)) {
                        kfifo_free(&node->ih_fifo);
                        dev_err(node->adev->dev, "Failed to allocate KFD IH workqueue\n");
                        return -ENOMEM;
                }
        }
        spin_lock_init(&node->interrupt_lock);

        INIT_WORK(&node->interrupt_work, interrupt_wq);

        node->interrupts_active = true;

        /*
         * After this function returns, the interrupt will be enabled. This
         * barrier ensures that the interrupt running on a different processor
         * sees all the above writes.
         */
        smp_wmb();

        return 0;
}

void kfd_interrupt_exit(struct kfd_node *node)
{
        /*
         * Stop the interrupt handler from writing to the ring and scheduling
         * workqueue items. The spinlock ensures that any interrupt running
         * after we have unlocked sees interrupts_active = false.
         */
        unsigned long flags;

        spin_lock_irqsave(&node->interrupt_lock, flags);
        node->interrupts_active = false;
        spin_unlock_irqrestore(&node->interrupt_lock, flags);
        kfifo_free(&node->ih_fifo);
}

/*
 * Assumption: single reader/writer. This function is not re-entrant
 */
bool enqueue_ih_ring_entry(struct kfd_node *node, const void *ih_ring_entry)
{
        if (kfifo_is_full(&node->ih_fifo)) {
                dev_warn_ratelimited(node->adev->dev, "KFD node %d ih_fifo overflow\n",
                                     node->node_id);
                return false;
        }

        kfifo_in(&node->ih_fifo, ih_ring_entry, node->kfd->device_info.ih_ring_entry_size);
        return true;
}

/*
 * Assumption: single reader/writer. This function is not re-entrant
 */
static bool dequeue_ih_ring_entry(struct kfd_node *node, u32 **ih_ring_entry)
{
        int count;

        if (kfifo_is_empty(&node->ih_fifo))
                return false;

        count = kfifo_out_linear_ptr(&node->ih_fifo, ih_ring_entry,
                                     node->kfd->device_info.ih_ring_entry_size);
        WARN_ON(count != node->kfd->device_info.ih_ring_entry_size);
        return count == node->kfd->device_info.ih_ring_entry_size;
}

static void interrupt_wq(struct work_struct *work)
{
        struct kfd_node *dev = container_of(work, struct kfd_node, interrupt_work);
        uint32_t *ih_ring_entry;
        unsigned long start_jiffies = jiffies;

        while (dequeue_ih_ring_entry(dev, &ih_ring_entry)) {
                dev->kfd->device_info.event_interrupt_class->interrupt_wq(dev,
                                                                ih_ring_entry);
                kfifo_skip_count(&dev->ih_fifo, dev->kfd->device_info.ih_ring_entry_size);

                if (time_is_before_jiffies(start_jiffies + HZ)) {
                        /* If we spent more than a second processing signals,
                         * reschedule the worker to avoid soft-lockup warnings
                         */
                        queue_work(dev->kfd->ih_wq, &dev->interrupt_work);
                        break;
                }
        }
}

bool interrupt_is_wanted(struct kfd_node *dev,
                        const uint32_t *ih_ring_entry,
                        uint32_t *patched_ihre, bool *flag)
{
        /* integer and bitwise OR so there is no boolean short-circuiting */
        unsigned int wanted = 0;

        wanted |= dev->kfd->device_info.event_interrupt_class->interrupt_isr(dev,
                                         ih_ring_entry, patched_ihre, flag);

        return wanted != 0;
}