/*
 * SPDX-License-Identifier: MIT
 *
 * Copyright © 2019 Intel Corporation
 */

#include "gem/i915_gem_object.h"
#include "i915_drv.h"
#include "i915_vma.h"
#include "intel_engine.h"
#include "intel_ring.h"
#include "intel_timeline.h"

unsigned int intel_ring_update_space(struct intel_ring *ring)
{
        unsigned int space;

        space = __intel_ring_space(ring->head, ring->emit, ring->size);

        ring->space = space;
        return space;
}

int intel_ring_pin(struct intel_ring *ring)
{
        struct i915_vma *vma = ring->vma;
        unsigned int flags;
        void *addr;
        int ret;

        if (atomic_fetch_inc(&ring->pin_count))
                return 0;

        flags = PIN_GLOBAL;

        /* Ring wraparound at offset 0 sometimes hangs. No idea why. */
        flags |= PIN_OFFSET_BIAS | i915_ggtt_pin_bias(vma);

        if (vma->obj->stolen)
                flags |= PIN_MAPPABLE;
        else
                flags |= PIN_HIGH;

        ret = i915_vma_pin(vma, 0, 0, flags);
        if (unlikely(ret))
                goto err_unpin;

        if (i915_vma_is_map_and_fenceable(vma))
                addr = (void __force *)i915_vma_pin_iomap(vma);
        else
                addr = i915_gem_object_pin_map(vma->obj,
                                               i915_coherent_map_type(vma->vm->i915));
        if (IS_ERR(addr)) {
                ret = PTR_ERR(addr);
                goto err_ring;
        }

        i915_vma_make_unshrinkable(vma);

        /* Discard any unused bytes beyond that submitted to hw. */
        intel_ring_reset(ring, ring->emit);

        ring->vaddr = addr;
        return 0;

err_ring:
        i915_vma_unpin(vma);
err_unpin:
        atomic_dec(&ring->pin_count);
        return ret;
}

void intel_ring_reset(struct intel_ring *ring, u32 tail)
{
        tail = intel_ring_wrap(ring, tail);
        ring->tail = tail;
        ring->head = tail;
        ring->emit = tail;
        intel_ring_update_space(ring);
}

void intel_ring_unpin(struct intel_ring *ring)
{
        struct i915_vma *vma = ring->vma;

        if (!atomic_dec_and_test(&ring->pin_count))
                return;

        i915_vma_unset_ggtt_write(vma);
        if (i915_vma_is_map_and_fenceable(vma))
                i915_vma_unpin_iomap(vma);
        else
                i915_gem_object_unpin_map(vma->obj);

        i915_vma_make_purgeable(vma);
        i915_vma_unpin(vma);
}

static struct i915_vma *create_ring_vma(struct i915_ggtt *ggtt, int size)
{
        struct i915_address_space *vm = &ggtt->vm;
        struct drm_i915_private *i915 = vm->i915;
        struct drm_i915_gem_object *obj;
        struct i915_vma *vma;

        obj = ERR_PTR(-ENODEV);
        if (i915_ggtt_has_aperture(ggtt))
                obj = i915_gem_object_create_stolen(i915, size);
        if (IS_ERR(obj))
                obj = i915_gem_object_create_internal(i915, size);
        if (IS_ERR(obj))
                return ERR_CAST(obj);

        /*
         * Mark ring buffers as read-only from GPU side (so no stray overwrites)
         * if supported by the platform's GGTT.
         */
        if (vm->has_read_only)
                i915_gem_object_set_readonly(obj);

        vma = i915_vma_instance(obj, vm, NULL);
        if (IS_ERR(vma))
                goto err;

        return vma;

err:
        i915_gem_object_put(obj);
        return vma;
}

struct intel_ring *
intel_engine_create_ring(struct intel_engine_cs *engine, int size)
{
        struct drm_i915_private *i915 = engine->i915;
        struct intel_ring *ring;
        struct i915_vma *vma;

        GEM_BUG_ON(!is_power_of_2(size));
        GEM_BUG_ON(RING_CTL_SIZE(size) & ~RING_NR_PAGES);

        ring = kzalloc(sizeof(*ring), GFP_KERNEL);
        if (!ring)
                return ERR_PTR(-ENOMEM);

        kref_init(&ring->ref);
        ring->size = size;
        ring->wrap = BITS_PER_TYPE(ring->size) - ilog2(size);

        /*
         * Workaround an erratum on the i830 which causes a hang if
         * the TAIL pointer points to within the last 2 cachelines
         * of the buffer.
         */
        ring->effective_size = size;
        if (IS_I830(i915) || IS_I845G(i915))
                ring->effective_size -= 2 * CACHELINE_BYTES;

        intel_ring_update_space(ring);

        vma = create_ring_vma(engine->gt->ggtt, size);
        if (IS_ERR(vma)) {
                kfree(ring);
                return ERR_CAST(vma);
        }
        ring->vma = vma;

        return ring;
}

void intel_ring_free(struct kref *ref)
{
        struct intel_ring *ring = container_of(ref, typeof(*ring), ref);

        i915_vma_put(ring->vma);
        kfree(ring);
}

static noinline int
wait_for_space(struct intel_ring *ring,
               struct intel_timeline *tl,
               unsigned int bytes)
{
        struct i915_request *target;
        long timeout;

        if (intel_ring_update_space(ring) >= bytes)
                return 0;

        GEM_BUG_ON(list_empty(&tl->requests));
        list_for_each_entry(target, &tl->requests, link) {
                if (target->ring != ring)
                        continue;

                /* Would completion of this request free enough space? */
                if (bytes <= __intel_ring_space(target->postfix,
                                                ring->emit, ring->size))
                        break;
        }

        if (GEM_WARN_ON(&target->link == &tl->requests))
                return -ENOSPC;

        timeout = i915_request_wait(target,
                                    I915_WAIT_INTERRUPTIBLE,
                                    MAX_SCHEDULE_TIMEOUT);
        if (timeout < 0)
                return timeout;

        i915_request_retire_upto(target);

        intel_ring_update_space(ring);
        GEM_BUG_ON(ring->space < bytes);
        return 0;
}

u32 *intel_ring_begin(struct i915_request *rq, unsigned int num_dwords)
{
        struct intel_ring *ring = rq->ring;
        const unsigned int remain_usable = ring->effective_size - ring->emit;
        const unsigned int bytes = num_dwords * sizeof(u32);
        unsigned int need_wrap = 0;
        unsigned int total_bytes;
        u32 *cs;

        /* Packets must be qword aligned. */
        GEM_BUG_ON(num_dwords & 1);

        total_bytes = bytes + rq->reserved_space;
        GEM_BUG_ON(total_bytes > ring->effective_size);

        if (unlikely(total_bytes > remain_usable)) {
                const int remain_actual = ring->size - ring->emit;

                if (bytes > remain_usable) {
                        /*
                         * Not enough space for the basic request. So need to
                         * flush out the remainder and then wait for
                         * base + reserved.
                         */
                        total_bytes += remain_actual;
                        need_wrap = remain_actual | 1;
                } else  {
                        /*
                         * The base request will fit but the reserved space
                         * falls off the end. So we don't need an immediate
                         * wrap and only need to effectively wait for the
                         * reserved size from the start of ringbuffer.
                         */
                        total_bytes = rq->reserved_space + remain_actual;
                }
        }

        if (unlikely(total_bytes > ring->space)) {
                int ret;

                /*
                 * Space is reserved in the ringbuffer for finalising the
                 * request, as that cannot be allowed to fail. During request
                 * finalisation, reserved_space is set to 0 to stop the
                 * overallocation and the assumption is that then we never need
                 * to wait (which has the risk of failing with EINTR).
                 *
                 * See also i915_request_alloc() and i915_request_add().
                 */
                GEM_BUG_ON(!rq->reserved_space);

                ret = wait_for_space(ring,
                                     i915_request_timeline(rq),
                                     total_bytes);
                if (unlikely(ret))
                        return ERR_PTR(ret);
        }

        if (unlikely(need_wrap)) {
                need_wrap &= ~1;
                GEM_BUG_ON(need_wrap > ring->space);
                GEM_BUG_ON(ring->emit + need_wrap > ring->size);
                GEM_BUG_ON(!IS_ALIGNED(need_wrap, sizeof(u64)));

                /* Fill the tail with MI_NOOP */
                memset64(ring->vaddr + ring->emit, 0, need_wrap / sizeof(u64));
                ring->space -= need_wrap;
                ring->emit = 0;
        }

        GEM_BUG_ON(ring->emit > ring->size - bytes);
        GEM_BUG_ON(ring->space < bytes);
        cs = ring->vaddr + ring->emit;
        GEM_DEBUG_EXEC(memset32(cs, POISON_INUSE, bytes / sizeof(*cs)));
        ring->emit += bytes;
        ring->space -= bytes;

        return cs;
}

/* Align the ring tail to a cacheline boundary */
int intel_ring_cacheline_align(struct i915_request *rq)
{
        int num_dwords;
        void *cs;

        num_dwords = (rq->ring->emit & (CACHELINE_BYTES - 1)) / sizeof(u32);
        if (num_dwords == 0)
                return 0;

        num_dwords = CACHELINE_DWORDS - num_dwords;
        GEM_BUG_ON(num_dwords & 1);

        cs = intel_ring_begin(rq, num_dwords);
        if (IS_ERR(cs))
                return PTR_ERR(cs);

        memset64(cs, (u64)MI_NOOP << 32 | MI_NOOP, num_dwords / 2);
        intel_ring_advance(rq, cs + num_dwords);

        GEM_BUG_ON(rq->ring->emit & (CACHELINE_BYTES - 1));
        return 0;
}

#if IS_ENABLED(CONFIG_DRM_I915_SELFTEST)
#include "selftest_ring.c"
#endif