// SPDX-License-Identifier: MIT
/*
 * Copyright © 2008-2021 Intel Corporation
 */

#include "gen2_engine_cs.h"
#include "gen6_engine_cs.h"
#include "gen6_ppgtt.h"
#include "gen7_renderclear.h"
#include "i915_drv.h"
#include "i915_mitigations.h"
#include "intel_breadcrumbs.h"
#include "intel_context.h"
#include "intel_gt.h"
#include "intel_gt_irq.h"
#include "intel_reset.h"
#include "intel_ring.h"
#include "shmem_utils.h"
#include "intel_engine_heartbeat.h"

/* Rough estimate of the typical request size, performing a flush,
 * set-context and then emitting the batch.
 */
#define LEGACY_REQUEST_SIZE 200

static void set_hwstam(struct intel_engine_cs *engine, u32 mask)
{
        /*
         * Keep the render interrupt unmasked as this papers over
         * lost interrupts following a reset.
         */
        if (engine->class == RENDER_CLASS) {
                if (GRAPHICS_VER(engine->i915) >= 6)
                        mask &= ~BIT(0);
                else
                        mask &= ~I915_USER_INTERRUPT;
        }

        intel_engine_set_hwsp_writemask(engine, mask);
}

static void set_hws_pga(struct intel_engine_cs *engine, phys_addr_t phys)
{
        u32 addr;

        addr = lower_32_bits(phys);
        if (GRAPHICS_VER(engine->i915) >= 4)
                addr |= (phys >> 28) & 0xf0;

        intel_uncore_write(engine->uncore, HWS_PGA, addr);
}

static struct page *status_page(struct intel_engine_cs *engine)
{
        struct drm_i915_gem_object *obj = engine->status_page.vma->obj;

        GEM_BUG_ON(!i915_gem_object_has_pinned_pages(obj));
        return sg_page(obj->mm.pages->sgl);
}

static void ring_setup_phys_status_page(struct intel_engine_cs *engine)
{
        set_hws_pga(engine, PFN_PHYS(page_to_pfn(status_page(engine))));
        set_hwstam(engine, ~0u);
}

static void set_hwsp(struct intel_engine_cs *engine, u32 offset)
{
        i915_reg_t hwsp;

        /*
         * The ring status page addresses are no longer next to the rest of
         * the ring registers as of gen7.
         */
        if (GRAPHICS_VER(engine->i915) == 7) {
                switch (engine->id) {
                /*
                 * No more rings exist on Gen7. Default case is only to shut up
                 * gcc switch check warning.
                 */
                default:
                        GEM_BUG_ON(engine->id);
                        fallthrough;
                case RCS0:
                        hwsp = RENDER_HWS_PGA_GEN7;
                        break;
                case BCS0:
                        hwsp = BLT_HWS_PGA_GEN7;
                        break;
                case VCS0:
                        hwsp = BSD_HWS_PGA_GEN7;
                        break;
                case VECS0:
                        hwsp = VEBOX_HWS_PGA_GEN7;
                        break;
                }
        } else if (GRAPHICS_VER(engine->i915) == 6) {
                hwsp = RING_HWS_PGA_GEN6(engine->mmio_base);
        } else {
                hwsp = RING_HWS_PGA(engine->mmio_base);
        }

        intel_uncore_write_fw(engine->uncore, hwsp, offset);
        intel_uncore_posting_read_fw(engine->uncore, hwsp);
}

static void flush_cs_tlb(struct intel_engine_cs *engine)
{
        if (!IS_GRAPHICS_VER(engine->i915, 6, 7))
                return;

        /* ring should be idle before issuing a sync flush*/
        GEM_DEBUG_WARN_ON((ENGINE_READ(engine, RING_MI_MODE) & MODE_IDLE) == 0);

        ENGINE_WRITE_FW(engine, RING_INSTPM,
                        _MASKED_BIT_ENABLE(INSTPM_TLB_INVALIDATE |
                                           INSTPM_SYNC_FLUSH));
        if (__intel_wait_for_register_fw(engine->uncore,
                                         RING_INSTPM(engine->mmio_base),
                                         INSTPM_SYNC_FLUSH, 0,
                                         2000, 0, NULL))
                ENGINE_TRACE(engine,
                             "wait for SyncFlush to complete for TLB invalidation timed out\n");
}

static void ring_setup_status_page(struct intel_engine_cs *engine)
{
        set_hwsp(engine, i915_ggtt_offset(engine->status_page.vma));
        set_hwstam(engine, ~0u);

        flush_cs_tlb(engine);
}

static struct i915_address_space *vm_alias(struct i915_address_space *vm)
{
        if (i915_is_ggtt(vm))
                vm = &i915_vm_to_ggtt(vm)->alias->vm;

        return vm;
}

static u32 pp_dir(struct i915_address_space *vm)
{
        return to_gen6_ppgtt(i915_vm_to_ppgtt(vm))->pp_dir;
}

static void set_pp_dir(struct intel_engine_cs *engine)
{
        struct i915_address_space *vm = vm_alias(engine->gt->vm);

        if (!vm)
                return;

        ENGINE_WRITE_FW(engine, RING_PP_DIR_DCLV, PP_DIR_DCLV_2G);
        ENGINE_WRITE_FW(engine, RING_PP_DIR_BASE, pp_dir(vm));

        if (GRAPHICS_VER(engine->i915) >= 7) {
                ENGINE_WRITE_FW(engine,
                                RING_MODE_GEN7,
                                _MASKED_BIT_ENABLE(GFX_PPGTT_ENABLE));
        }
}

static bool stop_ring(struct intel_engine_cs *engine)
{
        /* Empty the ring by skipping to the end */
        ENGINE_WRITE_FW(engine, RING_HEAD, ENGINE_READ_FW(engine, RING_TAIL));
        ENGINE_POSTING_READ(engine, RING_HEAD);

        /* The ring must be empty before it is disabled */
        ENGINE_WRITE_FW(engine, RING_CTL, 0);
        ENGINE_POSTING_READ(engine, RING_CTL);

        /* Then reset the disabled ring */
        ENGINE_WRITE_FW(engine, RING_HEAD, 0);
        ENGINE_WRITE_FW(engine, RING_TAIL, 0);

        return (ENGINE_READ_FW(engine, RING_HEAD) & HEAD_ADDR) == 0;
}

static int xcs_resume(struct intel_engine_cs *engine)
{
        struct intel_ring *ring = engine->legacy.ring;

        ENGINE_TRACE(engine, "ring:{HEAD:%04x, TAIL:%04x}\n",
                     ring->head, ring->tail);

        /*
         * Double check the ring is empty & disabled before we resume. Called
         * from atomic context during PCI probe, so _hardirq().
         */
        intel_synchronize_hardirq(engine->i915);
        if (!stop_ring(engine))
                goto err;

        if (HWS_NEEDS_PHYSICAL(engine->i915))
                ring_setup_phys_status_page(engine);
        else
                ring_setup_status_page(engine);

        intel_breadcrumbs_reset(engine->breadcrumbs);

        /* Enforce ordering by reading HEAD register back */
        ENGINE_POSTING_READ(engine, RING_HEAD);

        /*
         * Initialize the ring. This must happen _after_ we've cleared the ring
         * registers with the above sequence (the readback of the HEAD registers
         * also enforces ordering), otherwise the hw might lose the new ring
         * register values.
         */
        ENGINE_WRITE_FW(engine, RING_START, i915_ggtt_offset(ring->vma));

        /* Check that the ring offsets point within the ring! */
        GEM_BUG_ON(!intel_ring_offset_valid(ring, ring->head));
        GEM_BUG_ON(!intel_ring_offset_valid(ring, ring->tail));
        intel_ring_update_space(ring);

        set_pp_dir(engine);

        /* First wake the ring up to an empty/idle ring */
        ENGINE_WRITE_FW(engine, RING_HEAD, ring->head);
        ENGINE_WRITE_FW(engine, RING_TAIL, ring->head);
        ENGINE_POSTING_READ(engine, RING_TAIL);

        ENGINE_WRITE_FW(engine, RING_CTL,
                        RING_CTL_SIZE(ring->size) | RING_VALID);

        /* If the head is still not zero, the ring is dead */
        if (__intel_wait_for_register_fw(engine->uncore,
                                         RING_CTL(engine->mmio_base),
                                         RING_VALID, RING_VALID,
                                         5000, 0, NULL))
                goto err;

        if (GRAPHICS_VER(engine->i915) > 2)
                ENGINE_WRITE_FW(engine,
                                RING_MI_MODE, _MASKED_BIT_DISABLE(STOP_RING));

        /* Now awake, let it get started */
        if (ring->tail != ring->head) {
                ENGINE_WRITE_FW(engine, RING_TAIL, ring->tail);
                ENGINE_POSTING_READ(engine, RING_TAIL);
        }

        /* Papering over lost _interrupts_ immediately following the restart */
        intel_engine_signal_breadcrumbs(engine);
        return 0;

err:
        drm_err(&engine->i915->drm,
                "%s initialization failed; "
                "ctl %08x (valid? %d) head %08x [%08x] tail %08x [%08x] start %08x [expected %08x]\n",
                engine->name,
                ENGINE_READ(engine, RING_CTL),
                ENGINE_READ(engine, RING_CTL) & RING_VALID,
                ENGINE_READ(engine, RING_HEAD), ring->head,
                ENGINE_READ(engine, RING_TAIL), ring->tail,
                ENGINE_READ(engine, RING_START),
                i915_ggtt_offset(ring->vma));
        return -EIO;
}

static void sanitize_hwsp(struct intel_engine_cs *engine)
{
        struct intel_timeline *tl;

        list_for_each_entry(tl, &engine->status_page.timelines, engine_link)
                intel_timeline_reset_seqno(tl);
}

static void xcs_sanitize(struct intel_engine_cs *engine)
{
        /*
         * Poison residual state on resume, in case the suspend didn't!
         *
         * We have to assume that across suspend/resume (or other loss
         * of control) that the contents of our pinned buffers has been
         * lost, replaced by garbage. Since this doesn't always happen,
         * let's poison such state so that we more quickly spot when
         * we falsely assume it has been preserved.
         */
        if (IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM))
                memset(engine->status_page.addr, POISON_INUSE, PAGE_SIZE);

        /*
         * The kernel_context HWSP is stored in the status_page. As above,
         * that may be lost on resume/initialisation, and so we need to
         * reset the value in the HWSP.
         */
        sanitize_hwsp(engine);

        /* And scrub the dirty cachelines for the HWSP */
        clflush_cache_range(engine->status_page.addr, PAGE_SIZE);
}

static void reset_prepare(struct intel_engine_cs *engine)
{
        /*
         * We stop engines, otherwise we might get failed reset and a
         * dead gpu (on elk). Also as modern gpu as kbl can suffer
         * from system hang if batchbuffer is progressing when
         * the reset is issued, regardless of READY_TO_RESET ack.
         * Thus assume it is best to stop engines on all gens
         * where we have a gpu reset.
         *
         * WaKBLVECSSemaphoreWaitPoll:kbl (on ALL_ENGINES)
         *
         * WaMediaResetMainRingCleanup:ctg,elk (presumably)
         * WaClearRingBufHeadRegAtInit:ctg,elk
         *
         * FIXME: Wa for more modern gens needs to be validated
         */
        ENGINE_TRACE(engine, "\n");
        intel_engine_stop_cs(engine);

        if (!stop_ring(engine)) {
                /* G45 ring initialization often fails to reset head to zero */
                ENGINE_TRACE(engine,
                             "HEAD not reset to zero, "
                             "{ CTL:%08x, HEAD:%08x, TAIL:%08x, START:%08x }\n",
                             ENGINE_READ_FW(engine, RING_CTL),
                             ENGINE_READ_FW(engine, RING_HEAD),
                             ENGINE_READ_FW(engine, RING_TAIL),
                             ENGINE_READ_FW(engine, RING_START));
                if (!stop_ring(engine)) {
                        drm_err(&engine->i915->drm,
                                "failed to set %s head to zero "
                                "ctl %08x head %08x tail %08x start %08x\n",
                                engine->name,
                                ENGINE_READ_FW(engine, RING_CTL),
                                ENGINE_READ_FW(engine, RING_HEAD),
                                ENGINE_READ_FW(engine, RING_TAIL),
                                ENGINE_READ_FW(engine, RING_START));
                }
        }
}

static void reset_rewind(struct intel_engine_cs *engine, bool stalled)
{
        struct i915_request *pos, *rq;
        unsigned long flags;
        u32 head;

        rq = NULL;
        spin_lock_irqsave(&engine->sched_engine->lock, flags);
        rcu_read_lock();
        list_for_each_entry(pos, &engine->sched_engine->requests, sched.link) {
                if (!__i915_request_is_complete(pos)) {
                        rq = pos;
                        break;
                }
        }
        rcu_read_unlock();

        /*
         * The guilty request will get skipped on a hung engine.
         *
         * Users of client default contexts do not rely on logical
         * state preserved between batches so it is safe to execute
         * queued requests following the hang. Non default contexts
         * rely on preserved state, so skipping a batch loses the
         * evolution of the state and it needs to be considered corrupted.
         * Executing more queued batches on top of corrupted state is
         * risky. But we take the risk by trying to advance through
         * the queued requests in order to make the client behaviour
         * more predictable around resets, by not throwing away random
         * amount of batches it has prepared for execution. Sophisticated
         * clients can use gem_reset_stats_ioctl and dma fence status
         * (exported via sync_file info ioctl on explicit fences) to observe
         * when it loses the context state and should rebuild accordingly.
         *
         * The context ban, and ultimately the client ban, mechanism are safety
         * valves if client submission ends up resulting in nothing more than
         * subsequent hangs.
         */

        if (rq) {
                /*
                 * Try to restore the logical GPU state to match the
                 * continuation of the request queue. If we skip the
                 * context/PD restore, then the next request may try to execute
                 * assuming that its context is valid and loaded on the GPU and
                 * so may try to access invalid memory, prompting repeated GPU
                 * hangs.
                 *
                 * If the request was guilty, we still restore the logical
                 * state in case the next request requires it (e.g. the
                 * aliasing ppgtt), but skip over the hung batch.
                 *
                 * If the request was innocent, we try to replay the request
                 * with the restored context.
                 */
                __i915_request_reset(rq, stalled);

                GEM_BUG_ON(rq->ring != engine->legacy.ring);
                head = rq->head;
        } else {
                head = engine->legacy.ring->tail;
        }
        engine->legacy.ring->head = intel_ring_wrap(engine->legacy.ring, head);

        spin_unlock_irqrestore(&engine->sched_engine->lock, flags);
}

static void reset_finish(struct intel_engine_cs *engine)
{
}

static void reset_cancel(struct intel_engine_cs *engine)
{
        struct i915_request *request;
        unsigned long flags;

        spin_lock_irqsave(&engine->sched_engine->lock, flags);

        /* Mark all submitted requests as skipped. */
        list_for_each_entry(request, &engine->sched_engine->requests, sched.link)
                i915_request_put(i915_request_mark_eio(request));
        intel_engine_signal_breadcrumbs(engine);

        /* Remaining _unready_ requests will be nop'ed when submitted */

        spin_unlock_irqrestore(&engine->sched_engine->lock, flags);
}

static void i9xx_submit_request(struct i915_request *request)
{
        i915_request_submit(request);
        wmb(); /* paranoid flush writes out of the WCB before mmio */

        ENGINE_WRITE(request->engine, RING_TAIL,
                     intel_ring_set_tail(request->ring, request->tail));
}

static void __ring_context_fini(struct intel_context *ce)
{
        i915_vma_put(ce->state);
}

static void ring_context_destroy(struct kref *ref)
{
        struct intel_context *ce = container_of(ref, typeof(*ce), ref);

        GEM_BUG_ON(intel_context_is_pinned(ce));

        if (ce->state)
                __ring_context_fini(ce);

        intel_context_fini(ce);
        intel_context_free(ce);
}

static int ring_context_init_default_state(struct intel_context *ce,
                                           struct i915_gem_ww_ctx *ww)
{
        struct drm_i915_gem_object *obj = ce->state->obj;
        void *vaddr;

        vaddr = i915_gem_object_pin_map(obj, I915_MAP_WB);
        if (IS_ERR(vaddr))
                return PTR_ERR(vaddr);

        shmem_read(ce->engine->default_state, 0,
                   vaddr, ce->engine->context_size);

        i915_gem_object_flush_map(obj);
        __i915_gem_object_release_map(obj);

        __set_bit(CONTEXT_VALID_BIT, &ce->flags);
        return 0;
}

static int ring_context_pre_pin(struct intel_context *ce,
                                struct i915_gem_ww_ctx *ww,
                                void **unused)
{
        struct i915_address_space *vm;
        int err = 0;

        if (ce->engine->default_state &&
            !test_bit(CONTEXT_VALID_BIT, &ce->flags)) {
                err = ring_context_init_default_state(ce, ww);
                if (err)
                        return err;
        }

        vm = vm_alias(ce->vm);
        if (vm)
                err = gen6_ppgtt_pin(i915_vm_to_ppgtt((vm)), ww);

        return err;
}

static void __context_unpin_ppgtt(struct intel_context *ce)
{
        struct i915_address_space *vm;

        vm = vm_alias(ce->vm);
        if (vm)
                gen6_ppgtt_unpin(i915_vm_to_ppgtt(vm));
}

static void ring_context_unpin(struct intel_context *ce)
{
}

static void ring_context_post_unpin(struct intel_context *ce)
{
        __context_unpin_ppgtt(ce);
}

static struct i915_vma *
alloc_context_vma(struct intel_engine_cs *engine)
{
        struct drm_i915_private *i915 = engine->i915;
        struct drm_i915_gem_object *obj;
        struct i915_vma *vma;
        int err;

        obj = i915_gem_object_create_shmem(i915, engine->context_size);
        if (IS_ERR(obj))
                return ERR_CAST(obj);

        /*
         * Try to make the context utilize L3 as well as LLC.
         *
         * On VLV we don't have L3 controls in the PTEs so we
         * shouldn't touch the cache level, especially as that
         * would make the object snooped which might have a
         * negative performance impact.
         *
         * Snooping is required on non-llc platforms in execlist
         * mode, but since all GGTT accesses use PAT entry 0 we
         * get snooping anyway regardless of cache_level.
         *
         * This is only applicable for Ivy Bridge devices since
         * later platforms don't have L3 control bits in the PTE.
         */
        if (IS_IVYBRIDGE(i915))
                i915_gem_object_set_cache_coherency(obj, I915_CACHE_L3_LLC);

        vma = i915_vma_instance(obj, &engine->gt->ggtt->vm, NULL);
        if (IS_ERR(vma)) {
                err = PTR_ERR(vma);
                goto err_obj;
        }

        return vma;

err_obj:
        i915_gem_object_put(obj);
        return ERR_PTR(err);
}

static int ring_context_alloc(struct intel_context *ce)
{
        struct intel_engine_cs *engine = ce->engine;

        /* One ringbuffer to rule them all */
        GEM_BUG_ON(!engine->legacy.ring);
        ce->ring = engine->legacy.ring;
        ce->timeline = intel_timeline_get(engine->legacy.timeline);

        GEM_BUG_ON(ce->state);
        if (engine->context_size) {
                struct i915_vma *vma;

                vma = alloc_context_vma(engine);
                if (IS_ERR(vma))
                        return PTR_ERR(vma);

                ce->state = vma;
        }

        return 0;
}

static int ring_context_pin(struct intel_context *ce, void *unused)
{
        return 0;
}

static void ring_context_reset(struct intel_context *ce)
{
        intel_ring_reset(ce->ring, ce->ring->emit);
        clear_bit(CONTEXT_VALID_BIT, &ce->flags);
}

static void ring_context_ban(struct intel_context *ce,
                             struct i915_request *rq)
{
        struct intel_engine_cs *engine;

        if (!rq || !i915_request_is_active(rq))
                return;

        engine = rq->engine;
        lockdep_assert_held(&engine->sched_engine->lock);
        list_for_each_entry_continue(rq, &engine->sched_engine->requests,
                                     sched.link)
                if (rq->context == ce) {
                        i915_request_set_error_once(rq, -EIO);
                        __i915_request_skip(rq);
                }
}

static void ring_context_cancel_request(struct intel_context *ce,
                                        struct i915_request *rq)
{
        struct intel_engine_cs *engine = NULL;

        i915_request_active_engine(rq, &engine);

        if (engine && intel_engine_pulse(engine))
                intel_gt_handle_error(engine->gt, engine->mask, 0,
                                      "request cancellation by %s",
                                      current->comm);
}

static const struct intel_context_ops ring_context_ops = {
        .alloc = ring_context_alloc,

        .cancel_request = ring_context_cancel_request,

        .ban = ring_context_ban,

        .pre_pin = ring_context_pre_pin,
        .pin = ring_context_pin,
        .unpin = ring_context_unpin,
        .post_unpin = ring_context_post_unpin,

        .enter = intel_context_enter_engine,
        .exit = intel_context_exit_engine,

        .reset = ring_context_reset,
        .destroy = ring_context_destroy,
};

static int load_pd_dir(struct i915_request *rq,
                       struct i915_address_space *vm,
                       u32 valid)
{
        const struct intel_engine_cs * const engine = rq->engine;
        u32 *cs;

        cs = intel_ring_begin(rq, 12);
        if (IS_ERR(cs))
                return PTR_ERR(cs);

        *cs++ = MI_LOAD_REGISTER_IMM(1);
        *cs++ = i915_mmio_reg_offset(RING_PP_DIR_DCLV(engine->mmio_base));
        *cs++ = valid;

        *cs++ = MI_LOAD_REGISTER_IMM(1);
        *cs++ = i915_mmio_reg_offset(RING_PP_DIR_BASE(engine->mmio_base));
        *cs++ = pp_dir(vm);

        /* Stall until the page table load is complete? */
        *cs++ = MI_STORE_REGISTER_MEM | MI_SRM_LRM_GLOBAL_GTT;
        *cs++ = i915_mmio_reg_offset(RING_PP_DIR_BASE(engine->mmio_base));
        *cs++ = intel_gt_scratch_offset(engine->gt,
                                        INTEL_GT_SCRATCH_FIELD_DEFAULT);

        *cs++ = MI_LOAD_REGISTER_IMM(1);
        *cs++ = i915_mmio_reg_offset(RING_INSTPM(engine->mmio_base));
        *cs++ = _MASKED_BIT_ENABLE(INSTPM_TLB_INVALIDATE);

        intel_ring_advance(rq, cs);

        return rq->engine->emit_flush(rq, EMIT_FLUSH);
}

static int mi_set_context(struct i915_request *rq,
                          struct intel_context *ce,
                          u32 flags)
{
        struct intel_engine_cs *engine = rq->engine;
        struct drm_i915_private *i915 = engine->i915;
        enum intel_engine_id id;
        const int num_engines =
                IS_HASWELL(i915) ? engine->gt->info.num_engines - 1 : 0;
        bool force_restore = false;
        int len;
        u32 *cs;

        len = 4;
        if (GRAPHICS_VER(i915) == 7)
                len += 2 + (num_engines ? 4 * num_engines + 6 : 0);
        else if (GRAPHICS_VER(i915) == 5)
                len += 2;
        if (flags & MI_FORCE_RESTORE) {
                GEM_BUG_ON(flags & MI_RESTORE_INHIBIT);
                flags &= ~MI_FORCE_RESTORE;
                force_restore = true;
                len += 2;
        }

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

        /* WaProgramMiArbOnOffAroundMiSetContext:ivb,vlv,hsw,bdw,chv */
        if (GRAPHICS_VER(i915) == 7) {
                *cs++ = MI_ARB_ON_OFF | MI_ARB_DISABLE;
                if (num_engines) {
                        struct intel_engine_cs *signaller;

                        *cs++ = MI_LOAD_REGISTER_IMM(num_engines);
                        for_each_engine(signaller, engine->gt, id) {
                                if (signaller == engine)
                                        continue;

                                *cs++ = i915_mmio_reg_offset(
                                           RING_PSMI_CTL(signaller->mmio_base));
                                *cs++ = _MASKED_BIT_ENABLE(
                                                GEN6_PSMI_SLEEP_MSG_DISABLE);
                        }
                }
        } else if (GRAPHICS_VER(i915) == 5) {
                /*
                 * This w/a is only listed for pre-production ilk a/b steppings,
                 * but is also mentioned for programming the powerctx. To be
                 * safe, just apply the workaround; we do not use SyncFlush so
                 * this should never take effect and so be a no-op!
                 */
                *cs++ = MI_SUSPEND_FLUSH | MI_SUSPEND_FLUSH_EN;
        }

        if (force_restore) {
                /*
                 * The HW doesn't handle being told to restore the current
                 * context very well. Quite often it likes goes to go off and
                 * sulk, especially when it is meant to be reloading PP_DIR.
                 * A very simple fix to force the reload is to simply switch
                 * away from the current context and back again.
                 *
                 * Note that the kernel_context will contain random state
                 * following the INHIBIT_RESTORE. We accept this since we
                 * never use the kernel_context state; it is merely a
                 * placeholder we use to flush other contexts.
                 */
                *cs++ = MI_SET_CONTEXT;
                *cs++ = i915_ggtt_offset(engine->kernel_context->state) |
                        MI_MM_SPACE_GTT |
                        MI_RESTORE_INHIBIT;
        }

        *cs++ = MI_NOOP;
        *cs++ = MI_SET_CONTEXT;
        *cs++ = i915_ggtt_offset(ce->state) | flags;
        /*
         * w/a: MI_SET_CONTEXT must always be followed by MI_NOOP
         * WaMiSetContext_Hang:snb,ivb,vlv
         */
        *cs++ = MI_NOOP;

        if (GRAPHICS_VER(i915) == 7) {
                if (num_engines) {
                        struct intel_engine_cs *signaller;
                        i915_reg_t last_reg = {}; /* keep gcc quiet */

                        *cs++ = MI_LOAD_REGISTER_IMM(num_engines);
                        for_each_engine(signaller, engine->gt, id) {
                                if (signaller == engine)
                                        continue;

                                last_reg = RING_PSMI_CTL(signaller->mmio_base);
                                *cs++ = i915_mmio_reg_offset(last_reg);
                                *cs++ = _MASKED_BIT_DISABLE(
                                                GEN6_PSMI_SLEEP_MSG_DISABLE);
                        }

                        /* Insert a delay before the next switch! */
                        *cs++ = MI_STORE_REGISTER_MEM | MI_SRM_LRM_GLOBAL_GTT;
                        *cs++ = i915_mmio_reg_offset(last_reg);
                        *cs++ = intel_gt_scratch_offset(engine->gt,
                                                        INTEL_GT_SCRATCH_FIELD_DEFAULT);
                        *cs++ = MI_NOOP;
                }
                *cs++ = MI_ARB_ON_OFF | MI_ARB_ENABLE;
        } else if (GRAPHICS_VER(i915) == 5) {
                *cs++ = MI_SUSPEND_FLUSH;
        }

        intel_ring_advance(rq, cs);

        return 0;
}

static int remap_l3_slice(struct i915_request *rq, int slice)
{
#define L3LOG_DW (GEN7_L3LOG_SIZE / sizeof(u32))
        u32 *cs, *remap_info = rq->engine->i915->l3_parity.remap_info[slice];
        int i;

        if (!remap_info)
                return 0;

        cs = intel_ring_begin(rq, L3LOG_DW * 2 + 2);
        if (IS_ERR(cs))
                return PTR_ERR(cs);

        /*
         * Note: We do not worry about the concurrent register cacheline hang
         * here because no other code should access these registers other than
         * at initialization time.
         */
        *cs++ = MI_LOAD_REGISTER_IMM(L3LOG_DW);
        for (i = 0; i < L3LOG_DW; i++) {
                *cs++ = i915_mmio_reg_offset(GEN7_L3LOG(slice, i));
                *cs++ = remap_info[i];
        }
        *cs++ = MI_NOOP;
        intel_ring_advance(rq, cs);

        return 0;
#undef L3LOG_DW
}

static int remap_l3(struct i915_request *rq)
{
        struct i915_gem_context *ctx = i915_request_gem_context(rq);
        int i, err;

        if (!ctx || !ctx->remap_slice)
                return 0;

        for (i = 0; i < MAX_L3_SLICES; i++) {
                if (!(ctx->remap_slice & BIT(i)))
                        continue;

                err = remap_l3_slice(rq, i);
                if (err)
                        return err;
        }

        ctx->remap_slice = 0;
        return 0;
}

static int switch_mm(struct i915_request *rq, struct i915_address_space *vm)
{
        int ret;

        if (!vm)
                return 0;

        ret = rq->engine->emit_flush(rq, EMIT_FLUSH);
        if (ret)
                return ret;

        /*
         * Not only do we need a full barrier (post-sync write) after
         * invalidating the TLBs, but we need to wait a little bit
         * longer. Whether this is merely delaying us, or the
         * subsequent flush is a key part of serialising with the
         * post-sync op, this extra pass appears vital before a
         * mm switch!
         */
        ret = load_pd_dir(rq, vm, PP_DIR_DCLV_2G);
        if (ret)
                return ret;

        return rq->engine->emit_flush(rq, EMIT_INVALIDATE);
}

static int clear_residuals(struct i915_request *rq)
{
        struct intel_engine_cs *engine = rq->engine;
        int ret;

        ret = switch_mm(rq, vm_alias(engine->kernel_context->vm));
        if (ret)
                return ret;

        if (engine->kernel_context->state) {
                ret = mi_set_context(rq,
                                     engine->kernel_context,
                                     MI_MM_SPACE_GTT | MI_RESTORE_INHIBIT);
                if (ret)
                        return ret;
        }

        ret = engine->emit_bb_start(rq,
                                    engine->wa_ctx.vma->node.start, 0,
                                    0);
        if (ret)
                return ret;

        ret = engine->emit_flush(rq, EMIT_FLUSH);
        if (ret)
                return ret;

        /* Always invalidate before the next switch_mm() */
        return engine->emit_flush(rq, EMIT_INVALIDATE);
}

static int switch_context(struct i915_request *rq)
{
        struct intel_engine_cs *engine = rq->engine;
        struct intel_context *ce = rq->context;
        void **residuals = NULL;
        int ret;

        GEM_BUG_ON(HAS_EXECLISTS(engine->i915));

        if (engine->wa_ctx.vma && ce != engine->kernel_context) {
                if (engine->wa_ctx.vma->private != ce &&
                    i915_mitigate_clear_residuals()) {
                        ret = clear_residuals(rq);
                        if (ret)
                                return ret;

                        residuals = &engine->wa_ctx.vma->private;
                }
        }

        ret = switch_mm(rq, vm_alias(ce->vm));
        if (ret)
                return ret;

        if (ce->state) {
                u32 flags;

                GEM_BUG_ON(engine->id != RCS0);

                /* For resource streamer on HSW+ and power context elsewhere */
                BUILD_BUG_ON(HSW_MI_RS_SAVE_STATE_EN != MI_SAVE_EXT_STATE_EN);
                BUILD_BUG_ON(HSW_MI_RS_RESTORE_STATE_EN != MI_RESTORE_EXT_STATE_EN);

                flags = MI_SAVE_EXT_STATE_EN | MI_MM_SPACE_GTT;
                if (test_bit(CONTEXT_VALID_BIT, &ce->flags))
                        flags |= MI_RESTORE_EXT_STATE_EN;
                else
                        flags |= MI_RESTORE_INHIBIT;

                ret = mi_set_context(rq, ce, flags);
                if (ret)
                        return ret;
        }

        ret = remap_l3(rq);
        if (ret)
                return ret;

        /*
         * Now past the point of no return, this request _will_ be emitted.
         *
         * Or at least this preamble will be emitted, the request may be
         * interrupted prior to submitting the user payload. If so, we
         * still submit the "empty" request in order to preserve global
         * state tracking such as this, our tracking of the current
         * dirty context.
         */
        if (residuals) {
                intel_context_put(*residuals);
                *residuals = intel_context_get(ce);
        }

        return 0;
}

static int ring_request_alloc(struct i915_request *request)
{
        int ret;

        GEM_BUG_ON(!intel_context_is_pinned(request->context));
        GEM_BUG_ON(i915_request_timeline(request)->has_initial_breadcrumb);

        /*
         * Flush enough space to reduce the likelihood of waiting after
         * we start building the request - in which case we will just
         * have to repeat work.
         */
        request->reserved_space += LEGACY_REQUEST_SIZE;

        /* Unconditionally invalidate GPU caches and TLBs. */
        ret = request->engine->emit_flush(request, EMIT_INVALIDATE);
        if (ret)
                return ret;

        ret = switch_context(request);
        if (ret)
                return ret;

        request->reserved_space -= LEGACY_REQUEST_SIZE;
        return 0;
}

static void gen6_bsd_submit_request(struct i915_request *request)
{
        struct intel_uncore *uncore = request->engine->uncore;

        intel_uncore_forcewake_get(uncore, FORCEWAKE_ALL);

       /* Every tail move must follow the sequence below */

        /* Disable notification that the ring is IDLE. The GT
         * will then assume that it is busy and bring it out of rc6.

         */
        intel_uncore_write_fw(uncore, GEN6_BSD_SLEEP_PSMI_CONTROL,
                              _MASKED_BIT_ENABLE(GEN6_BSD_SLEEP_MSG_DISABLE));

        /* Clear the context id. Here be magic! */
        intel_uncore_write64_fw(uncore, GEN6_BSD_RNCID, 0x0);

        /* Wait for the ring not to be idle, i.e. for it to wake up. */
        if (__intel_wait_for_register_fw(uncore,
                                         GEN6_BSD_SLEEP_PSMI_CONTROL,
                                         GEN6_BSD_SLEEP_INDICATOR,
                                         0,
                                         1000, 0, NULL))
                drm_err(&uncore->i915->drm,
                        "timed out waiting for the BSD ring to wake up\n");

        /* Now that the ring is fully powered up, update the tail */
        i9xx_submit_request(request);

        /* Let the ring send IDLE messages to the GT again,
         * and so let it sleep to conserve power when idle.
         */
        intel_uncore_write_fw(uncore, GEN6_BSD_SLEEP_PSMI_CONTROL,
                              _MASKED_BIT_DISABLE(GEN6_BSD_SLEEP_MSG_DISABLE));

        intel_uncore_forcewake_put(uncore, FORCEWAKE_ALL);
}

static void i9xx_set_default_submission(struct intel_engine_cs *engine)
{
        engine->submit_request = i9xx_submit_request;
}

static void gen6_bsd_set_default_submission(struct intel_engine_cs *engine)
{
        engine->submit_request = gen6_bsd_submit_request;
}

static void ring_release(struct intel_engine_cs *engine)
{
        struct drm_i915_private *dev_priv = engine->i915;

        drm_WARN_ON(&dev_priv->drm, GRAPHICS_VER(dev_priv) > 2 &&
                    (ENGINE_READ(engine, RING_MI_MODE) & MODE_IDLE) == 0);

        intel_engine_cleanup_common(engine);

        if (engine->wa_ctx.vma) {
                intel_context_put(engine->wa_ctx.vma->private);
                i915_vma_unpin_and_release(&engine->wa_ctx.vma, 0);
        }

        intel_ring_unpin(engine->legacy.ring);
        intel_ring_put(engine->legacy.ring);

        intel_timeline_unpin(engine->legacy.timeline);
        intel_timeline_put(engine->legacy.timeline);
}

static void irq_handler(struct intel_engine_cs *engine, u16 iir)
{
        intel_engine_signal_breadcrumbs(engine);
}

static void setup_irq(struct intel_engine_cs *engine)
{
        struct drm_i915_private *i915 = engine->i915;

        intel_engine_set_irq_handler(engine, irq_handler);

        if (GRAPHICS_VER(i915) >= 6) {
                engine->irq_enable = gen6_irq_enable;
                engine->irq_disable = gen6_irq_disable;
        } else if (GRAPHICS_VER(i915) >= 5) {
                engine->irq_enable = gen5_irq_enable;
                engine->irq_disable = gen5_irq_disable;
        } else if (GRAPHICS_VER(i915) >= 3) {
                engine->irq_enable = gen3_irq_enable;
                engine->irq_disable = gen3_irq_disable;
        } else {
                engine->irq_enable = gen2_irq_enable;
                engine->irq_disable = gen2_irq_disable;
        }
}

static void add_to_engine(struct i915_request *rq)
{
        lockdep_assert_held(&rq->engine->sched_engine->lock);
        list_move_tail(&rq->sched.link, &rq->engine->sched_engine->requests);
}

static void remove_from_engine(struct i915_request *rq)
{
        spin_lock_irq(&rq->engine->sched_engine->lock);
        list_del_init(&rq->sched.link);

        /* Prevent further __await_execution() registering a cb, then flush */
        set_bit(I915_FENCE_FLAG_ACTIVE, &rq->fence.flags);

        spin_unlock_irq(&rq->engine->sched_engine->lock);

        i915_request_notify_execute_cb_imm(rq);
}

static void setup_common(struct intel_engine_cs *engine)
{
        struct drm_i915_private *i915 = engine->i915;

        /* gen8+ are only supported with execlists */
        GEM_BUG_ON(GRAPHICS_VER(i915) >= 8);

        setup_irq(engine);

        engine->resume = xcs_resume;
        engine->sanitize = xcs_sanitize;

        engine->reset.prepare = reset_prepare;
        engine->reset.rewind = reset_rewind;
        engine->reset.cancel = reset_cancel;
        engine->reset.finish = reset_finish;

        engine->add_active_request = add_to_engine;
        engine->remove_active_request = remove_from_engine;

        engine->cops = &ring_context_ops;
        engine->request_alloc = ring_request_alloc;

        /*
         * Using a global execution timeline; the previous final breadcrumb is
         * equivalent to our next initial bread so we can elide
         * engine->emit_init_breadcrumb().
         */
        engine->emit_fini_breadcrumb = gen3_emit_breadcrumb;
        if (GRAPHICS_VER(i915) == 5)
                engine->emit_fini_breadcrumb = gen5_emit_breadcrumb;

        engine->set_default_submission = i9xx_set_default_submission;

        if (GRAPHICS_VER(i915) >= 6)
                engine->emit_bb_start = gen6_emit_bb_start;
        else if (GRAPHICS_VER(i915) >= 4)
                engine->emit_bb_start = gen4_emit_bb_start;
        else if (IS_I830(i915) || IS_I845G(i915))
                engine->emit_bb_start = i830_emit_bb_start;
        else
                engine->emit_bb_start = gen3_emit_bb_start;
}

static void setup_rcs(struct intel_engine_cs *engine)
{
        struct drm_i915_private *i915 = engine->i915;

        if (HAS_L3_DPF(i915))
                engine->irq_keep_mask = GT_RENDER_L3_PARITY_ERROR_INTERRUPT;

        engine->irq_enable_mask = GT_RENDER_USER_INTERRUPT;

        if (GRAPHICS_VER(i915) >= 7) {
                engine->emit_flush = gen7_emit_flush_rcs;
                engine->emit_fini_breadcrumb = gen7_emit_breadcrumb_rcs;
        } else if (GRAPHICS_VER(i915) == 6) {
                engine->emit_flush = gen6_emit_flush_rcs;
                engine->emit_fini_breadcrumb = gen6_emit_breadcrumb_rcs;
        } else if (GRAPHICS_VER(i915) == 5) {
                engine->emit_flush = gen4_emit_flush_rcs;
        } else {
                if (GRAPHICS_VER(i915) < 4)
                        engine->emit_flush = gen2_emit_flush;
                else
                        engine->emit_flush = gen4_emit_flush_rcs;
                engine->irq_enable_mask = I915_USER_INTERRUPT;
        }

        if (IS_HASWELL(i915))
                engine->emit_bb_start = hsw_emit_bb_start;
}

static void setup_vcs(struct intel_engine_cs *engine)
{
        struct drm_i915_private *i915 = engine->i915;

        if (GRAPHICS_VER(i915) >= 6) {
                /* gen6 bsd needs a special wa for tail updates */
                if (GRAPHICS_VER(i915) == 6)
                        engine->set_default_submission = gen6_bsd_set_default_submission;
                engine->emit_flush = gen6_emit_flush_vcs;
                engine->irq_enable_mask = GT_BSD_USER_INTERRUPT;

                if (GRAPHICS_VER(i915) == 6)
                        engine->emit_fini_breadcrumb = gen6_emit_breadcrumb_xcs;
                else
                        engine->emit_fini_breadcrumb = gen7_emit_breadcrumb_xcs;
        } else {
                engine->emit_flush = gen4_emit_flush_vcs;
                if (GRAPHICS_VER(i915) == 5)
                        engine->irq_enable_mask = ILK_BSD_USER_INTERRUPT;
                else
                        engine->irq_enable_mask = I915_BSD_USER_INTERRUPT;
        }
}

static void setup_bcs(struct intel_engine_cs *engine)
{
        struct drm_i915_private *i915 = engine->i915;

        engine->emit_flush = gen6_emit_flush_xcs;
        engine->irq_enable_mask = GT_BLT_USER_INTERRUPT;

        if (GRAPHICS_VER(i915) == 6)
                engine->emit_fini_breadcrumb = gen6_emit_breadcrumb_xcs;
        else
                engine->emit_fini_breadcrumb = gen7_emit_breadcrumb_xcs;
}

static void setup_vecs(struct intel_engine_cs *engine)
{
        struct drm_i915_private *i915 = engine->i915;

        GEM_BUG_ON(GRAPHICS_VER(i915) < 7);

        engine->emit_flush = gen6_emit_flush_xcs;
        engine->irq_enable_mask = PM_VEBOX_USER_INTERRUPT;
        engine->irq_enable = hsw_irq_enable_vecs;
        engine->irq_disable = hsw_irq_disable_vecs;

        engine->emit_fini_breadcrumb = gen7_emit_breadcrumb_xcs;
}

static int gen7_ctx_switch_bb_setup(struct intel_engine_cs * const engine,
                                    struct i915_vma * const vma)
{
        return gen7_setup_clear_gpr_bb(engine, vma);
}

static int gen7_ctx_switch_bb_init(struct intel_engine_cs *engine,
                                   struct i915_gem_ww_ctx *ww,
                                   struct i915_vma *vma)
{
        int err;

        err = i915_vma_pin_ww(vma, ww, 0, 0, PIN_USER | PIN_HIGH);
        if (err)
                return err;

        err = i915_vma_sync(vma);
        if (err)
                goto err_unpin;

        err = gen7_ctx_switch_bb_setup(engine, vma);
        if (err)
                goto err_unpin;

        engine->wa_ctx.vma = vma;
        return 0;

err_unpin:
        i915_vma_unpin(vma);
        return err;
}

static struct i915_vma *gen7_ctx_vma(struct intel_engine_cs *engine)
{
        struct drm_i915_gem_object *obj;
        struct i915_vma *vma;
        int size, err;

        if (GRAPHICS_VER(engine->i915) != 7 || engine->class != RENDER_CLASS)
                return 0;

        err = gen7_ctx_switch_bb_setup(engine, NULL /* probe size */);
        if (err < 0)
                return ERR_PTR(err);
        if (!err)
                return NULL;

        size = ALIGN(err, PAGE_SIZE);

        obj = i915_gem_object_create_internal(engine->i915, size);
        if (IS_ERR(obj))
                return ERR_CAST(obj);

        vma = i915_vma_instance(obj, engine->gt->vm, NULL);
        if (IS_ERR(vma)) {
                i915_gem_object_put(obj);
                return ERR_CAST(vma);
        }

        vma->private = intel_context_create(engine); /* dummy residuals */
        if (IS_ERR(vma->private)) {
                err = PTR_ERR(vma->private);
                vma->private = NULL;
                i915_gem_object_put(obj);
                return ERR_PTR(err);
        }

        return vma;
}

int intel_ring_submission_setup(struct intel_engine_cs *engine)
{
        struct i915_gem_ww_ctx ww;
        struct intel_timeline *timeline;
        struct intel_ring *ring;
        struct i915_vma *gen7_wa_vma;
        int err;

        setup_common(engine);

        switch (engine->class) {
        case RENDER_CLASS:
                setup_rcs(engine);
                break;
        case VIDEO_DECODE_CLASS:
                setup_vcs(engine);
                break;
        case COPY_ENGINE_CLASS:
                setup_bcs(engine);
                break;
        case VIDEO_ENHANCEMENT_CLASS:
                setup_vecs(engine);
                break;
        default:
                MISSING_CASE(engine->class);
                return -ENODEV;
        }

        timeline = intel_timeline_create_from_engine(engine,
                                                     I915_GEM_HWS_SEQNO_ADDR);
        if (IS_ERR(timeline)) {
                err = PTR_ERR(timeline);
                goto err;
        }
        GEM_BUG_ON(timeline->has_initial_breadcrumb);

        ring = intel_engine_create_ring(engine, SZ_16K);
        if (IS_ERR(ring)) {
                err = PTR_ERR(ring);
                goto err_timeline;
        }

        GEM_BUG_ON(engine->legacy.ring);
        engine->legacy.ring = ring;
        engine->legacy.timeline = timeline;

        gen7_wa_vma = gen7_ctx_vma(engine);
        if (IS_ERR(gen7_wa_vma)) {
                err = PTR_ERR(gen7_wa_vma);
                goto err_ring;
        }

        i915_gem_ww_ctx_init(&ww, false);

retry:
        err = i915_gem_object_lock(timeline->hwsp_ggtt->obj, &ww);
        if (!err && gen7_wa_vma)
                err = i915_gem_object_lock(gen7_wa_vma->obj, &ww);
        if (!err && engine->legacy.ring->vma->obj)
                err = i915_gem_object_lock(engine->legacy.ring->vma->obj, &ww);
        if (!err)
                err = intel_timeline_pin(timeline, &ww);
        if (!err) {
                err = intel_ring_pin(ring, &ww);
                if (err)
                        intel_timeline_unpin(timeline);
        }
        if (err)
                goto out;

        GEM_BUG_ON(timeline->hwsp_ggtt != engine->status_page.vma);

        if (gen7_wa_vma) {
                err = gen7_ctx_switch_bb_init(engine, &ww, gen7_wa_vma);
                if (err) {
                        intel_ring_unpin(ring);
                        intel_timeline_unpin(timeline);
                }
        }

out:
        if (err == -EDEADLK) {
                err = i915_gem_ww_ctx_backoff(&ww);
                if (!err)
                        goto retry;
        }
        i915_gem_ww_ctx_fini(&ww);
        if (err)
                goto err_gen7_put;

        /* Finally, take ownership and responsibility for cleanup! */
        engine->release = ring_release;

        return 0;

err_gen7_put:
        if (gen7_wa_vma) {
                intel_context_put(gen7_wa_vma->private);
                i915_gem_object_put(gen7_wa_vma->obj);
        }
err_ring:
        intel_ring_put(ring);
err_timeline:
        intel_timeline_put(timeline);
err:
        intel_engine_cleanup_common(engine);
        return err;
}

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