WIP FPC-III support

[linux/fpc-iii.git] / drivers / gpu / drm / i915 / gt / intel_reset.c

/*
 * SPDX-License-Identifier: MIT
 *
 * Copyright © 2008-2018 Intel Corporation
 */

#include <linux/sched/mm.h>
#include <linux/stop_machine.h>

#include "display/intel_display_types.h"
#include "display/intel_overlay.h"

#include "gem/i915_gem_context.h"

#include "i915_drv.h"
#include "i915_gpu_error.h"
#include "i915_irq.h"
#include "intel_breadcrumbs.h"
#include "intel_engine_pm.h"
#include "intel_gt.h"
#include "intel_gt_pm.h"
#include "intel_gt_requests.h"
#include "intel_reset.h"

#include "uc/intel_guc.h"
#include "uc/intel_guc_submission.h"

#define RESET_MAX_RETRIES 3

/* XXX How to handle concurrent GGTT updates using tiling registers? */
#define RESET_UNDER_STOP_MACHINE 0

static void rmw_set_fw(struct intel_uncore *uncore, i915_reg_t reg, u32 set)
{
        intel_uncore_rmw_fw(uncore, reg, 0, set);
}

static void rmw_clear_fw(struct intel_uncore *uncore, i915_reg_t reg, u32 clr)
{
        intel_uncore_rmw_fw(uncore, reg, clr, 0);
}

static void engine_skip_context(struct i915_request *rq)
{
        struct intel_engine_cs *engine = rq->engine;
        struct intel_context *hung_ctx = rq->context;

        if (!i915_request_is_active(rq))
                return;

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

static void client_mark_guilty(struct i915_gem_context *ctx, bool banned)
{
        struct drm_i915_file_private *file_priv = ctx->file_priv;
        unsigned long prev_hang;
        unsigned int score;

        if (IS_ERR_OR_NULL(file_priv))
                return;

        score = 0;
        if (banned)
                score = I915_CLIENT_SCORE_CONTEXT_BAN;

        prev_hang = xchg(&file_priv->hang_timestamp, jiffies);
        if (time_before(jiffies, prev_hang + I915_CLIENT_FAST_HANG_JIFFIES))
                score += I915_CLIENT_SCORE_HANG_FAST;

        if (score) {
                atomic_add(score, &file_priv->ban_score);

                drm_dbg(&ctx->i915->drm,
                        "client %s: gained %u ban score, now %u\n",
                        ctx->name, score,
                        atomic_read(&file_priv->ban_score));
        }
}

static bool mark_guilty(struct i915_request *rq)
{
        struct i915_gem_context *ctx;
        unsigned long prev_hang;
        bool banned;
        int i;

        if (intel_context_is_closed(rq->context)) {
                intel_context_set_banned(rq->context);
                return true;
        }

        rcu_read_lock();
        ctx = rcu_dereference(rq->context->gem_context);
        if (ctx && !kref_get_unless_zero(&ctx->ref))
                ctx = NULL;
        rcu_read_unlock();
        if (!ctx)
                return intel_context_is_banned(rq->context);

        atomic_inc(&ctx->guilty_count);

        /* Cool contexts are too cool to be banned! (Used for reset testing.) */
        if (!i915_gem_context_is_bannable(ctx)) {
                banned = false;
                goto out;
        }

        drm_notice(&ctx->i915->drm,
                   "%s context reset due to GPU hang\n",
                   ctx->name);

        /* Record the timestamp for the last N hangs */
        prev_hang = ctx->hang_timestamp[0];
        for (i = 0; i < ARRAY_SIZE(ctx->hang_timestamp) - 1; i++)
                ctx->hang_timestamp[i] = ctx->hang_timestamp[i + 1];
        ctx->hang_timestamp[i] = jiffies;

        /* If we have hung N+1 times in rapid succession, we ban the context! */
        banned = !i915_gem_context_is_recoverable(ctx);
        if (time_before(jiffies, prev_hang + CONTEXT_FAST_HANG_JIFFIES))
                banned = true;
        if (banned) {
                drm_dbg(&ctx->i915->drm, "context %s: guilty %d, banned\n",
                        ctx->name, atomic_read(&ctx->guilty_count));
                intel_context_set_banned(rq->context);
        }

        client_mark_guilty(ctx, banned);

out:
        i915_gem_context_put(ctx);
        return banned;
}

static void mark_innocent(struct i915_request *rq)
{
        struct i915_gem_context *ctx;

        rcu_read_lock();
        ctx = rcu_dereference(rq->context->gem_context);
        if (ctx)
                atomic_inc(&ctx->active_count);
        rcu_read_unlock();
}

void __i915_request_reset(struct i915_request *rq, bool guilty)
{
        RQ_TRACE(rq, "guilty? %s\n", yesno(guilty));

        GEM_BUG_ON(i915_request_completed(rq));

        rcu_read_lock(); /* protect the GEM context */
        if (guilty) {
                i915_request_set_error_once(rq, -EIO);
                __i915_request_skip(rq);
                if (mark_guilty(rq))
                        engine_skip_context(rq);
        } else {
                i915_request_set_error_once(rq, -EAGAIN);
                mark_innocent(rq);
        }
        rcu_read_unlock();
}

static bool i915_in_reset(struct pci_dev *pdev)
{
        u8 gdrst;

        pci_read_config_byte(pdev, I915_GDRST, &gdrst);
        return gdrst & GRDOM_RESET_STATUS;
}

static int i915_do_reset(struct intel_gt *gt,
                         intel_engine_mask_t engine_mask,
                         unsigned int retry)
{
        struct pci_dev *pdev = gt->i915->drm.pdev;
        int err;

        /* Assert reset for at least 20 usec, and wait for acknowledgement. */
        pci_write_config_byte(pdev, I915_GDRST, GRDOM_RESET_ENABLE);
        udelay(50);
        err = wait_for_atomic(i915_in_reset(pdev), 50);

        /* Clear the reset request. */
        pci_write_config_byte(pdev, I915_GDRST, 0);
        udelay(50);
        if (!err)
                err = wait_for_atomic(!i915_in_reset(pdev), 50);

        return err;
}

static bool g4x_reset_complete(struct pci_dev *pdev)
{
        u8 gdrst;

        pci_read_config_byte(pdev, I915_GDRST, &gdrst);
        return (gdrst & GRDOM_RESET_ENABLE) == 0;
}

static int g33_do_reset(struct intel_gt *gt,
                        intel_engine_mask_t engine_mask,
                        unsigned int retry)
{
        struct pci_dev *pdev = gt->i915->drm.pdev;

        pci_write_config_byte(pdev, I915_GDRST, GRDOM_RESET_ENABLE);
        return wait_for_atomic(g4x_reset_complete(pdev), 50);
}

static int g4x_do_reset(struct intel_gt *gt,
                        intel_engine_mask_t engine_mask,
                        unsigned int retry)
{
        struct pci_dev *pdev = gt->i915->drm.pdev;
        struct intel_uncore *uncore = gt->uncore;
        int ret;

        /* WaVcpClkGateDisableForMediaReset:ctg,elk */
        rmw_set_fw(uncore, VDECCLK_GATE_D, VCP_UNIT_CLOCK_GATE_DISABLE);
        intel_uncore_posting_read_fw(uncore, VDECCLK_GATE_D);

        pci_write_config_byte(pdev, I915_GDRST,
                              GRDOM_MEDIA | GRDOM_RESET_ENABLE);
        ret =  wait_for_atomic(g4x_reset_complete(pdev), 50);
        if (ret) {
                drm_dbg(&gt->i915->drm, "Wait for media reset failed\n");
                goto out;
        }

        pci_write_config_byte(pdev, I915_GDRST,
                              GRDOM_RENDER | GRDOM_RESET_ENABLE);
        ret =  wait_for_atomic(g4x_reset_complete(pdev), 50);
        if (ret) {
                drm_dbg(&gt->i915->drm, "Wait for render reset failed\n");
                goto out;
        }

out:
        pci_write_config_byte(pdev, I915_GDRST, 0);

        rmw_clear_fw(uncore, VDECCLK_GATE_D, VCP_UNIT_CLOCK_GATE_DISABLE);
        intel_uncore_posting_read_fw(uncore, VDECCLK_GATE_D);

        return ret;
}

static int ilk_do_reset(struct intel_gt *gt, intel_engine_mask_t engine_mask,
                        unsigned int retry)
{
        struct intel_uncore *uncore = gt->uncore;
        int ret;

        intel_uncore_write_fw(uncore, ILK_GDSR,
                              ILK_GRDOM_RENDER | ILK_GRDOM_RESET_ENABLE);
        ret = __intel_wait_for_register_fw(uncore, ILK_GDSR,
                                           ILK_GRDOM_RESET_ENABLE, 0,
                                           5000, 0,
                                           NULL);
        if (ret) {
                drm_dbg(&gt->i915->drm, "Wait for render reset failed\n");
                goto out;
        }

        intel_uncore_write_fw(uncore, ILK_GDSR,
                              ILK_GRDOM_MEDIA | ILK_GRDOM_RESET_ENABLE);
        ret = __intel_wait_for_register_fw(uncore, ILK_GDSR,
                                           ILK_GRDOM_RESET_ENABLE, 0,
                                           5000, 0,
                                           NULL);
        if (ret) {
                drm_dbg(&gt->i915->drm, "Wait for media reset failed\n");
                goto out;
        }

out:
        intel_uncore_write_fw(uncore, ILK_GDSR, 0);
        intel_uncore_posting_read_fw(uncore, ILK_GDSR);
        return ret;
}

/* Reset the hardware domains (GENX_GRDOM_*) specified by mask */
static int gen6_hw_domain_reset(struct intel_gt *gt, u32 hw_domain_mask)
{
        struct intel_uncore *uncore = gt->uncore;
        int err;

        /*
         * GEN6_GDRST is not in the gt power well, no need to check
         * for fifo space for the write or forcewake the chip for
         * the read
         */
        intel_uncore_write_fw(uncore, GEN6_GDRST, hw_domain_mask);

        /* Wait for the device to ack the reset requests */
        err = __intel_wait_for_register_fw(uncore,
                                           GEN6_GDRST, hw_domain_mask, 0,
                                           500, 0,
                                           NULL);
        if (err)
                drm_dbg(&gt->i915->drm,
                        "Wait for 0x%08x engines reset failed\n",
                        hw_domain_mask);

        return err;
}

static int gen6_reset_engines(struct intel_gt *gt,
                              intel_engine_mask_t engine_mask,
                              unsigned int retry)
{
        static const u32 hw_engine_mask[] = {
                [RCS0]  = GEN6_GRDOM_RENDER,
                [BCS0]  = GEN6_GRDOM_BLT,
                [VCS0]  = GEN6_GRDOM_MEDIA,
                [VCS1]  = GEN8_GRDOM_MEDIA2,
                [VECS0] = GEN6_GRDOM_VECS,
        };
        struct intel_engine_cs *engine;
        u32 hw_mask;

        if (engine_mask == ALL_ENGINES) {
                hw_mask = GEN6_GRDOM_FULL;
        } else {
                intel_engine_mask_t tmp;

                hw_mask = 0;
                for_each_engine_masked(engine, gt, engine_mask, tmp) {
                        GEM_BUG_ON(engine->id >= ARRAY_SIZE(hw_engine_mask));
                        hw_mask |= hw_engine_mask[engine->id];
                }
        }

        return gen6_hw_domain_reset(gt, hw_mask);
}

static int gen11_lock_sfc(struct intel_engine_cs *engine, u32 *hw_mask)
{
        struct intel_uncore *uncore = engine->uncore;
        u8 vdbox_sfc_access = engine->gt->info.vdbox_sfc_access;
        i915_reg_t sfc_forced_lock, sfc_forced_lock_ack;
        u32 sfc_forced_lock_bit, sfc_forced_lock_ack_bit;
        i915_reg_t sfc_usage;
        u32 sfc_usage_bit;
        u32 sfc_reset_bit;
        int ret;

        switch (engine->class) {
        case VIDEO_DECODE_CLASS:
                if ((BIT(engine->instance) & vdbox_sfc_access) == 0)
                        return 0;

                sfc_forced_lock = GEN11_VCS_SFC_FORCED_LOCK(engine);
                sfc_forced_lock_bit = GEN11_VCS_SFC_FORCED_LOCK_BIT;

                sfc_forced_lock_ack = GEN11_VCS_SFC_LOCK_STATUS(engine);
                sfc_forced_lock_ack_bit  = GEN11_VCS_SFC_LOCK_ACK_BIT;

                sfc_usage = GEN11_VCS_SFC_LOCK_STATUS(engine);
                sfc_usage_bit = GEN11_VCS_SFC_USAGE_BIT;
                sfc_reset_bit = GEN11_VCS_SFC_RESET_BIT(engine->instance);
                break;

        case VIDEO_ENHANCEMENT_CLASS:
                sfc_forced_lock = GEN11_VECS_SFC_FORCED_LOCK(engine);
                sfc_forced_lock_bit = GEN11_VECS_SFC_FORCED_LOCK_BIT;

                sfc_forced_lock_ack = GEN11_VECS_SFC_LOCK_ACK(engine);
                sfc_forced_lock_ack_bit  = GEN11_VECS_SFC_LOCK_ACK_BIT;

                sfc_usage = GEN11_VECS_SFC_USAGE(engine);
                sfc_usage_bit = GEN11_VECS_SFC_USAGE_BIT;
                sfc_reset_bit = GEN11_VECS_SFC_RESET_BIT(engine->instance);
                break;

        default:
                return 0;
        }

        /*
         * If the engine is using a SFC, tell the engine that a software reset
         * is going to happen. The engine will then try to force lock the SFC.
         * If SFC ends up being locked to the engine we want to reset, we have
         * to reset it as well (we will unlock it once the reset sequence is
         * completed).
         */
        if (!(intel_uncore_read_fw(uncore, sfc_usage) & sfc_usage_bit))
                return 0;

        rmw_set_fw(uncore, sfc_forced_lock, sfc_forced_lock_bit);

        ret = __intel_wait_for_register_fw(uncore,
                                           sfc_forced_lock_ack,
                                           sfc_forced_lock_ack_bit,
                                           sfc_forced_lock_ack_bit,
                                           1000, 0, NULL);

        /* Was the SFC released while we were trying to lock it? */
        if (!(intel_uncore_read_fw(uncore, sfc_usage) & sfc_usage_bit))
                return 0;

        if (ret) {
                drm_dbg(&engine->i915->drm,
                        "Wait for SFC forced lock ack failed\n");
                return ret;
        }

        *hw_mask |= sfc_reset_bit;
        return 0;
}

static void gen11_unlock_sfc(struct intel_engine_cs *engine)
{
        struct intel_uncore *uncore = engine->uncore;
        u8 vdbox_sfc_access = engine->gt->info.vdbox_sfc_access;
        i915_reg_t sfc_forced_lock;
        u32 sfc_forced_lock_bit;

        switch (engine->class) {
        case VIDEO_DECODE_CLASS:
                if ((BIT(engine->instance) & vdbox_sfc_access) == 0)
                        return;

                sfc_forced_lock = GEN11_VCS_SFC_FORCED_LOCK(engine);
                sfc_forced_lock_bit = GEN11_VCS_SFC_FORCED_LOCK_BIT;
                break;

        case VIDEO_ENHANCEMENT_CLASS:
                sfc_forced_lock = GEN11_VECS_SFC_FORCED_LOCK(engine);
                sfc_forced_lock_bit = GEN11_VECS_SFC_FORCED_LOCK_BIT;
                break;

        default:
                return;
        }

        rmw_clear_fw(uncore, sfc_forced_lock, sfc_forced_lock_bit);
}

static int gen11_reset_engines(struct intel_gt *gt,
                               intel_engine_mask_t engine_mask,
                               unsigned int retry)
{
        static const u32 hw_engine_mask[] = {
                [RCS0]  = GEN11_GRDOM_RENDER,
                [BCS0]  = GEN11_GRDOM_BLT,
                [VCS0]  = GEN11_GRDOM_MEDIA,
                [VCS1]  = GEN11_GRDOM_MEDIA2,
                [VCS2]  = GEN11_GRDOM_MEDIA3,
                [VCS3]  = GEN11_GRDOM_MEDIA4,
                [VECS0] = GEN11_GRDOM_VECS,
                [VECS1] = GEN11_GRDOM_VECS2,
        };
        struct intel_engine_cs *engine;
        intel_engine_mask_t tmp;
        u32 hw_mask;
        int ret;

        if (engine_mask == ALL_ENGINES) {
                hw_mask = GEN11_GRDOM_FULL;
        } else {
                hw_mask = 0;
                for_each_engine_masked(engine, gt, engine_mask, tmp) {
                        GEM_BUG_ON(engine->id >= ARRAY_SIZE(hw_engine_mask));
                        hw_mask |= hw_engine_mask[engine->id];
                        ret = gen11_lock_sfc(engine, &hw_mask);
                        if (ret)
                                goto sfc_unlock;
                }
        }

        ret = gen6_hw_domain_reset(gt, hw_mask);

sfc_unlock:
        /*
         * We unlock the SFC based on the lock status and not the result of
         * gen11_lock_sfc to make sure that we clean properly if something
         * wrong happened during the lock (e.g. lock acquired after timeout
         * expiration).
         */
        if (engine_mask != ALL_ENGINES)
                for_each_engine_masked(engine, gt, engine_mask, tmp)
                        gen11_unlock_sfc(engine);

        return ret;
}

static int gen8_engine_reset_prepare(struct intel_engine_cs *engine)
{
        struct intel_uncore *uncore = engine->uncore;
        const i915_reg_t reg = RING_RESET_CTL(engine->mmio_base);
        u32 request, mask, ack;
        int ret;

        ack = intel_uncore_read_fw(uncore, reg);
        if (ack & RESET_CTL_CAT_ERROR) {
                /*
                 * For catastrophic errors, ready-for-reset sequence
                 * needs to be bypassed: HAS#396813
                 */
                request = RESET_CTL_CAT_ERROR;
                mask = RESET_CTL_CAT_ERROR;

                /* Catastrophic errors need to be cleared by HW */
                ack = 0;
        } else if (!(ack & RESET_CTL_READY_TO_RESET)) {
                request = RESET_CTL_REQUEST_RESET;
                mask = RESET_CTL_READY_TO_RESET;
                ack = RESET_CTL_READY_TO_RESET;
        } else {
                return 0;
        }

        intel_uncore_write_fw(uncore, reg, _MASKED_BIT_ENABLE(request));
        ret = __intel_wait_for_register_fw(uncore, reg, mask, ack,
                                           700, 0, NULL);
        if (ret)
                drm_err(&engine->i915->drm,
                        "%s reset request timed out: {request: %08x, RESET_CTL: %08x}\n",
                        engine->name, request,
                        intel_uncore_read_fw(uncore, reg));

        return ret;
}

static void gen8_engine_reset_cancel(struct intel_engine_cs *engine)
{
        intel_uncore_write_fw(engine->uncore,
                              RING_RESET_CTL(engine->mmio_base),
                              _MASKED_BIT_DISABLE(RESET_CTL_REQUEST_RESET));
}

static int gen8_reset_engines(struct intel_gt *gt,
                              intel_engine_mask_t engine_mask,
                              unsigned int retry)
{
        struct intel_engine_cs *engine;
        const bool reset_non_ready = retry >= 1;
        intel_engine_mask_t tmp;
        int ret;

        for_each_engine_masked(engine, gt, engine_mask, tmp) {
                ret = gen8_engine_reset_prepare(engine);
                if (ret && !reset_non_ready)
                        goto skip_reset;

                /*
                 * If this is not the first failed attempt to prepare,
                 * we decide to proceed anyway.
                 *
                 * By doing so we risk context corruption and with
                 * some gens (kbl), possible system hang if reset
                 * happens during active bb execution.
                 *
                 * We rather take context corruption instead of
                 * failed reset with a wedged driver/gpu. And
                 * active bb execution case should be covered by
                 * stop_engines() we have before the reset.
                 */
        }

        if (INTEL_GEN(gt->i915) >= 11)
                ret = gen11_reset_engines(gt, engine_mask, retry);
        else
                ret = gen6_reset_engines(gt, engine_mask, retry);

skip_reset:
        for_each_engine_masked(engine, gt, engine_mask, tmp)
                gen8_engine_reset_cancel(engine);

        return ret;
}

static int mock_reset(struct intel_gt *gt,
                      intel_engine_mask_t mask,
                      unsigned int retry)
{
        return 0;
}

typedef int (*reset_func)(struct intel_gt *,
                          intel_engine_mask_t engine_mask,
                          unsigned int retry);

static reset_func intel_get_gpu_reset(const struct intel_gt *gt)
{
        struct drm_i915_private *i915 = gt->i915;

        if (is_mock_gt(gt))
                return mock_reset;
        else if (INTEL_GEN(i915) >= 8)
                return gen8_reset_engines;
        else if (INTEL_GEN(i915) >= 6)
                return gen6_reset_engines;
        else if (INTEL_GEN(i915) >= 5)
                return ilk_do_reset;
        else if (IS_G4X(i915))
                return g4x_do_reset;
        else if (IS_G33(i915) || IS_PINEVIEW(i915))
                return g33_do_reset;
        else if (INTEL_GEN(i915) >= 3)
                return i915_do_reset;
        else
                return NULL;
}

int __intel_gt_reset(struct intel_gt *gt, intel_engine_mask_t engine_mask)
{
        const int retries = engine_mask == ALL_ENGINES ? RESET_MAX_RETRIES : 1;
        reset_func reset;
        int ret = -ETIMEDOUT;
        int retry;

        reset = intel_get_gpu_reset(gt);
        if (!reset)
                return -ENODEV;

        /*
         * If the power well sleeps during the reset, the reset
         * request may be dropped and never completes (causing -EIO).
         */
        intel_uncore_forcewake_get(gt->uncore, FORCEWAKE_ALL);
        for (retry = 0; ret == -ETIMEDOUT && retry < retries; retry++) {
                GT_TRACE(gt, "engine_mask=%x\n", engine_mask);
                preempt_disable();
                ret = reset(gt, engine_mask, retry);
                preempt_enable();
        }
        intel_uncore_forcewake_put(gt->uncore, FORCEWAKE_ALL);

        return ret;
}

bool intel_has_gpu_reset(const struct intel_gt *gt)
{
        if (!gt->i915->params.reset)
                return NULL;

        return intel_get_gpu_reset(gt);
}

bool intel_has_reset_engine(const struct intel_gt *gt)
{
        if (gt->i915->params.reset < 2)
                return false;

        return INTEL_INFO(gt->i915)->has_reset_engine;
}

int intel_reset_guc(struct intel_gt *gt)
{
        u32 guc_domain =
                INTEL_GEN(gt->i915) >= 11 ? GEN11_GRDOM_GUC : GEN9_GRDOM_GUC;
        int ret;

        GEM_BUG_ON(!HAS_GT_UC(gt->i915));

        intel_uncore_forcewake_get(gt->uncore, FORCEWAKE_ALL);
        ret = gen6_hw_domain_reset(gt, guc_domain);
        intel_uncore_forcewake_put(gt->uncore, FORCEWAKE_ALL);

        return ret;
}

/*
 * Ensure irq handler finishes, and not run again.
 * Also return the active request so that we only search for it once.
 */
static void reset_prepare_engine(struct intel_engine_cs *engine)
{
        /*
         * During the reset sequence, we must prevent the engine from
         * entering RC6. As the context state is undefined until we restart
         * the engine, if it does enter RC6 during the reset, the state
         * written to the powercontext is undefined and so we may lose
         * GPU state upon resume, i.e. fail to restart after a reset.
         */
        intel_uncore_forcewake_get(engine->uncore, FORCEWAKE_ALL);
        if (engine->reset.prepare)
                engine->reset.prepare(engine);
}

static void revoke_mmaps(struct intel_gt *gt)
{
        int i;

        for (i = 0; i < gt->ggtt->num_fences; i++) {
                struct drm_vma_offset_node *node;
                struct i915_vma *vma;
                u64 vma_offset;

                vma = READ_ONCE(gt->ggtt->fence_regs[i].vma);
                if (!vma)
                        continue;

                if (!i915_vma_has_userfault(vma))
                        continue;

                GEM_BUG_ON(vma->fence != &gt->ggtt->fence_regs[i]);

                if (!vma->mmo)
                        continue;

                node = &vma->mmo->vma_node;
                vma_offset = vma->ggtt_view.partial.offset << PAGE_SHIFT;

                unmap_mapping_range(gt->i915->drm.anon_inode->i_mapping,
                                    drm_vma_node_offset_addr(node) + vma_offset,
                                    vma->size,
                                    1);
        }
}

static intel_engine_mask_t reset_prepare(struct intel_gt *gt)
{
        struct intel_engine_cs *engine;
        intel_engine_mask_t awake = 0;
        enum intel_engine_id id;

        for_each_engine(engine, gt, id) {
                if (intel_engine_pm_get_if_awake(engine))
                        awake |= engine->mask;
                reset_prepare_engine(engine);
        }

        intel_uc_reset_prepare(&gt->uc);

        return awake;
}

static void gt_revoke(struct intel_gt *gt)
{
        revoke_mmaps(gt);
}

static int gt_reset(struct intel_gt *gt, intel_engine_mask_t stalled_mask)
{
        struct intel_engine_cs *engine;
        enum intel_engine_id id;
        int err;

        /*
         * Everything depends on having the GTT running, so we need to start
         * there.
         */
        err = i915_ggtt_enable_hw(gt->i915);
        if (err)
                return err;

        for_each_engine(engine, gt, id)
                __intel_engine_reset(engine, stalled_mask & engine->mask);

        intel_ggtt_restore_fences(gt->ggtt);

        return err;
}

static void reset_finish_engine(struct intel_engine_cs *engine)
{
        if (engine->reset.finish)
                engine->reset.finish(engine);
        intel_uncore_forcewake_put(engine->uncore, FORCEWAKE_ALL);

        intel_engine_signal_breadcrumbs(engine);
}

static void reset_finish(struct intel_gt *gt, intel_engine_mask_t awake)
{
        struct intel_engine_cs *engine;
        enum intel_engine_id id;

        for_each_engine(engine, gt, id) {
                reset_finish_engine(engine);
                if (awake & engine->mask)
                        intel_engine_pm_put(engine);
        }
}

static void nop_submit_request(struct i915_request *request)
{
        struct intel_engine_cs *engine = request->engine;
        unsigned long flags;

        RQ_TRACE(request, "-EIO\n");
        i915_request_set_error_once(request, -EIO);

        spin_lock_irqsave(&engine->active.lock, flags);
        __i915_request_submit(request);
        i915_request_mark_complete(request);
        spin_unlock_irqrestore(&engine->active.lock, flags);

        intel_engine_signal_breadcrumbs(engine);
}

static void __intel_gt_set_wedged(struct intel_gt *gt)
{
        struct intel_engine_cs *engine;
        intel_engine_mask_t awake;
        enum intel_engine_id id;

        if (test_bit(I915_WEDGED, &gt->reset.flags))
                return;

        GT_TRACE(gt, "start\n");

        /*
         * First, stop submission to hw, but do not yet complete requests by
         * rolling the global seqno forward (since this would complete requests
         * for which we haven't set the fence error to EIO yet).
         */
        awake = reset_prepare(gt);

        /* Even if the GPU reset fails, it should still stop the engines */
        if (!INTEL_INFO(gt->i915)->gpu_reset_clobbers_display)
                __intel_gt_reset(gt, ALL_ENGINES);

        for_each_engine(engine, gt, id)
                engine->submit_request = nop_submit_request;

        /*
         * Make sure no request can slip through without getting completed by
         * either this call here to intel_engine_write_global_seqno, or the one
         * in nop_submit_request.
         */
        synchronize_rcu_expedited();
        set_bit(I915_WEDGED, &gt->reset.flags);

        /* Mark all executing requests as skipped */
        for_each_engine(engine, gt, id)
                if (engine->reset.cancel)
                        engine->reset.cancel(engine);

        reset_finish(gt, awake);

        GT_TRACE(gt, "end\n");
}

void intel_gt_set_wedged(struct intel_gt *gt)
{
        intel_wakeref_t wakeref;

        if (test_bit(I915_WEDGED, &gt->reset.flags))
                return;

        wakeref = intel_runtime_pm_get(gt->uncore->rpm);
        mutex_lock(&gt->reset.mutex);

        if (GEM_SHOW_DEBUG()) {
                struct drm_printer p = drm_debug_printer(__func__);
                struct intel_engine_cs *engine;
                enum intel_engine_id id;

                drm_printf(&p, "called from %pS\n", (void *)_RET_IP_);
                for_each_engine(engine, gt, id) {
                        if (intel_engine_is_idle(engine))
                                continue;

                        intel_engine_dump(engine, &p, "%s\n", engine->name);
                }
        }

        __intel_gt_set_wedged(gt);

        mutex_unlock(&gt->reset.mutex);
        intel_runtime_pm_put(gt->uncore->rpm, wakeref);
}

static bool __intel_gt_unset_wedged(struct intel_gt *gt)
{
        struct intel_gt_timelines *timelines = &gt->timelines;
        struct intel_timeline *tl;
        bool ok;

        if (!test_bit(I915_WEDGED, &gt->reset.flags))
                return true;

        /* Never fully initialised, recovery impossible */
        if (intel_gt_has_unrecoverable_error(gt))
                return false;

        GT_TRACE(gt, "start\n");

        /*
         * Before unwedging, make sure that all pending operations
         * are flushed and errored out - we may have requests waiting upon
         * third party fences. We marked all inflight requests as EIO, and
         * every execbuf since returned EIO, for consistency we want all
         * the currently pending requests to also be marked as EIO, which
         * is done inside our nop_submit_request - and so we must wait.
         *
         * No more can be submitted until we reset the wedged bit.
         */
        spin_lock(&timelines->lock);
        list_for_each_entry(tl, &timelines->active_list, link) {
                struct dma_fence *fence;

                fence = i915_active_fence_get(&tl->last_request);
                if (!fence)
                        continue;

                spin_unlock(&timelines->lock);

                /*
                 * All internal dependencies (i915_requests) will have
                 * been flushed by the set-wedge, but we may be stuck waiting
                 * for external fences. These should all be capped to 10s
                 * (I915_FENCE_TIMEOUT) so this wait should not be unbounded
                 * in the worst case.
                 */
                dma_fence_default_wait(fence, false, MAX_SCHEDULE_TIMEOUT);
                dma_fence_put(fence);

                /* Restart iteration after droping lock */
                spin_lock(&timelines->lock);
                tl = list_entry(&timelines->active_list, typeof(*tl), link);
        }
        spin_unlock(&timelines->lock);

        /* We must reset pending GPU events before restoring our submission */
        ok = !HAS_EXECLISTS(gt->i915); /* XXX better agnosticism desired */
        if (!INTEL_INFO(gt->i915)->gpu_reset_clobbers_display)
                ok = __intel_gt_reset(gt, ALL_ENGINES) == 0;
        if (!ok) {
                /*
                 * Warn CI about the unrecoverable wedged condition.
                 * Time for a reboot.
                 */
                add_taint_for_CI(gt->i915, TAINT_WARN);
                return false;
        }

        /*
         * Undo nop_submit_request. We prevent all new i915 requests from
         * being queued (by disallowing execbuf whilst wedged) so having
         * waited for all active requests above, we know the system is idle
         * and do not have to worry about a thread being inside
         * engine->submit_request() as we swap over. So unlike installing
         * the nop_submit_request on reset, we can do this from normal
         * context and do not require stop_machine().
         */
        intel_engines_reset_default_submission(gt);

        GT_TRACE(gt, "end\n");

        smp_mb__before_atomic(); /* complete takeover before enabling execbuf */
        clear_bit(I915_WEDGED, &gt->reset.flags);

        return true;
}

bool intel_gt_unset_wedged(struct intel_gt *gt)
{
        bool result;

        mutex_lock(&gt->reset.mutex);
        result = __intel_gt_unset_wedged(gt);
        mutex_unlock(&gt->reset.mutex);

        return result;
}

static int do_reset(struct intel_gt *gt, intel_engine_mask_t stalled_mask)
{
        int err, i;

        gt_revoke(gt);

        err = __intel_gt_reset(gt, ALL_ENGINES);
        for (i = 0; err && i < RESET_MAX_RETRIES; i++) {
                msleep(10 * (i + 1));
                err = __intel_gt_reset(gt, ALL_ENGINES);
        }
        if (err)
                return err;

        return gt_reset(gt, stalled_mask);
}

static int resume(struct intel_gt *gt)
{
        struct intel_engine_cs *engine;
        enum intel_engine_id id;
        int ret;

        for_each_engine(engine, gt, id) {
                ret = intel_engine_resume(engine);
                if (ret)
                        return ret;
        }

        return 0;
}

/**
 * intel_gt_reset - reset chip after a hang
 * @gt: #intel_gt to reset
 * @stalled_mask: mask of the stalled engines with the guilty requests
 * @reason: user error message for why we are resetting
 *
 * Reset the chip.  Useful if a hang is detected. Marks the device as wedged
 * on failure.
 *
 * Procedure is fairly simple:
 *   - reset the chip using the reset reg
 *   - re-init context state
 *   - re-init hardware status page
 *   - re-init ring buffer
 *   - re-init interrupt state
 *   - re-init display
 */
void intel_gt_reset(struct intel_gt *gt,
                    intel_engine_mask_t stalled_mask,
                    const char *reason)
{
        intel_engine_mask_t awake;
        int ret;

        GT_TRACE(gt, "flags=%lx\n", gt->reset.flags);

        might_sleep();
        GEM_BUG_ON(!test_bit(I915_RESET_BACKOFF, &gt->reset.flags));
        mutex_lock(&gt->reset.mutex);

        /* Clear any previous failed attempts at recovery. Time to try again. */
        if (!__intel_gt_unset_wedged(gt))
                goto unlock;

        if (reason)
                drm_notice(&gt->i915->drm,
                           "Resetting chip for %s\n", reason);
        atomic_inc(&gt->i915->gpu_error.reset_count);

        awake = reset_prepare(gt);

        if (!intel_has_gpu_reset(gt)) {
                if (gt->i915->params.reset)
                        drm_err(&gt->i915->drm, "GPU reset not supported\n");
                else
                        drm_dbg(&gt->i915->drm, "GPU reset disabled\n");
                goto error;
        }

        if (INTEL_INFO(gt->i915)->gpu_reset_clobbers_display)
                intel_runtime_pm_disable_interrupts(gt->i915);

        if (do_reset(gt, stalled_mask)) {
                drm_err(&gt->i915->drm, "Failed to reset chip\n");
                goto taint;
        }

        if (INTEL_INFO(gt->i915)->gpu_reset_clobbers_display)
                intel_runtime_pm_enable_interrupts(gt->i915);

        intel_overlay_reset(gt->i915);

        /*
         * Next we need to restore the context, but we don't use those
         * yet either...
         *
         * Ring buffer needs to be re-initialized in the KMS case, or if X
         * was running at the time of the reset (i.e. we weren't VT
         * switched away).
         */
        ret = intel_gt_init_hw(gt);
        if (ret) {
                drm_err(&gt->i915->drm,
                        "Failed to initialise HW following reset (%d)\n",
                        ret);
                goto taint;
        }

        ret = resume(gt);
        if (ret)
                goto taint;

finish:
        reset_finish(gt, awake);
unlock:
        mutex_unlock(&gt->reset.mutex);
        return;

taint:
        /*
         * History tells us that if we cannot reset the GPU now, we
         * never will. This then impacts everything that is run
         * subsequently. On failing the reset, we mark the driver
         * as wedged, preventing further execution on the GPU.
         * We also want to go one step further and add a taint to the
         * kernel so that any subsequent faults can be traced back to
         * this failure. This is important for CI, where if the
         * GPU/driver fails we would like to reboot and restart testing
         * rather than continue on into oblivion. For everyone else,
         * the system should still plod along, but they have been warned!
         */
        add_taint_for_CI(gt->i915, TAINT_WARN);
error:
        __intel_gt_set_wedged(gt);
        goto finish;
}

static inline int intel_gt_reset_engine(struct intel_engine_cs *engine)
{
        return __intel_gt_reset(engine->gt, engine->mask);
}

/**
 * intel_engine_reset - reset GPU engine to recover from a hang
 * @engine: engine to reset
 * @msg: reason for GPU reset; or NULL for no drm_notice()
 *
 * Reset a specific GPU engine. Useful if a hang is detected.
 * Returns zero on successful reset or otherwise an error code.
 *
 * Procedure is:
 *  - identifies the request that caused the hang and it is dropped
 *  - reset engine (which will force the engine to idle)
 *  - re-init/configure engine
 */
int intel_engine_reset(struct intel_engine_cs *engine, const char *msg)
{
        struct intel_gt *gt = engine->gt;
        bool uses_guc = intel_engine_in_guc_submission_mode(engine);
        int ret;

        ENGINE_TRACE(engine, "flags=%lx\n", gt->reset.flags);
        GEM_BUG_ON(!test_bit(I915_RESET_ENGINE + engine->id, &gt->reset.flags));

        if (!intel_engine_pm_get_if_awake(engine))
                return 0;

        reset_prepare_engine(engine);

        if (msg)
                drm_notice(&engine->i915->drm,
                           "Resetting %s for %s\n", engine->name, msg);
        atomic_inc(&engine->i915->gpu_error.reset_engine_count[engine->uabi_class]);

        if (!uses_guc)
                ret = intel_gt_reset_engine(engine);
        else
                ret = intel_guc_reset_engine(&engine->gt->uc.guc, engine);
        if (ret) {
                /* If we fail here, we expect to fallback to a global reset */
                drm_dbg(&gt->i915->drm, "%sFailed to reset %s, ret=%d\n",
                        uses_guc ? "GuC " : "", engine->name, ret);
                goto out;
        }

        /*
         * The request that caused the hang is stuck on elsp, we know the
         * active request and can drop it, adjust head to skip the offending
         * request to resume executing remaining requests in the queue.
         */
        __intel_engine_reset(engine, true);

        /*
         * The engine and its registers (and workarounds in case of render)
         * have been reset to their default values. Follow the init_ring
         * process to program RING_MODE, HWSP and re-enable submission.
         */
        ret = intel_engine_resume(engine);

out:
        intel_engine_cancel_stop_cs(engine);
        reset_finish_engine(engine);
        intel_engine_pm_put_async(engine);
        return ret;
}

static void intel_gt_reset_global(struct intel_gt *gt,
                                  u32 engine_mask,
                                  const char *reason)
{
        struct kobject *kobj = &gt->i915->drm.primary->kdev->kobj;
        char *error_event[] = { I915_ERROR_UEVENT "=1", NULL };
        char *reset_event[] = { I915_RESET_UEVENT "=1", NULL };
        char *reset_done_event[] = { I915_ERROR_UEVENT "=0", NULL };
        struct intel_wedge_me w;

        kobject_uevent_env(kobj, KOBJ_CHANGE, error_event);

        drm_dbg(&gt->i915->drm, "resetting chip, engines=%x\n", engine_mask);
        kobject_uevent_env(kobj, KOBJ_CHANGE, reset_event);

        /* Use a watchdog to ensure that our reset completes */
        intel_wedge_on_timeout(&w, gt, 5 * HZ) {
                intel_display_prepare_reset(gt->i915);

                /* Flush everyone using a resource about to be clobbered */
                synchronize_srcu_expedited(&gt->reset.backoff_srcu);

                intel_gt_reset(gt, engine_mask, reason);

                intel_display_finish_reset(gt->i915);
        }

        if (!test_bit(I915_WEDGED, &gt->reset.flags))
                kobject_uevent_env(kobj, KOBJ_CHANGE, reset_done_event);
}

/**
 * intel_gt_handle_error - handle a gpu error
 * @gt: the intel_gt
 * @engine_mask: mask representing engines that are hung
 * @flags: control flags
 * @fmt: Error message format string
 *
 * Do some basic checking of register state at error time and
 * dump it to the syslog.  Also call i915_capture_error_state() to make
 * sure we get a record and make it available in debugfs.  Fire a uevent
 * so userspace knows something bad happened (should trigger collection
 * of a ring dump etc.).
 */
void intel_gt_handle_error(struct intel_gt *gt,
                           intel_engine_mask_t engine_mask,
                           unsigned long flags,
                           const char *fmt, ...)
{
        struct intel_engine_cs *engine;
        intel_wakeref_t wakeref;
        intel_engine_mask_t tmp;
        char error_msg[80];
        char *msg = NULL;

        if (fmt) {
                va_list args;

                va_start(args, fmt);
                vscnprintf(error_msg, sizeof(error_msg), fmt, args);
                va_end(args);

                msg = error_msg;
        }

        /*
         * In most cases it's guaranteed that we get here with an RPM
         * reference held, for example because there is a pending GPU
         * request that won't finish until the reset is done. This
         * isn't the case at least when we get here by doing a
         * simulated reset via debugfs, so get an RPM reference.
         */
        wakeref = intel_runtime_pm_get(gt->uncore->rpm);

        engine_mask &= gt->info.engine_mask;

        if (flags & I915_ERROR_CAPTURE) {
                i915_capture_error_state(gt, engine_mask);
                intel_gt_clear_error_registers(gt, engine_mask);
        }

        /*
         * Try engine reset when available. We fall back to full reset if
         * single reset fails.
         */
        if (intel_has_reset_engine(gt) && !intel_gt_is_wedged(gt)) {
                for_each_engine_masked(engine, gt, engine_mask, tmp) {
                        BUILD_BUG_ON(I915_RESET_MODESET >= I915_RESET_ENGINE);
                        if (test_and_set_bit(I915_RESET_ENGINE + engine->id,
                                             &gt->reset.flags))
                                continue;

                        if (intel_engine_reset(engine, msg) == 0)
                                engine_mask &= ~engine->mask;

                        clear_and_wake_up_bit(I915_RESET_ENGINE + engine->id,
                                              &gt->reset.flags);
                }
        }

        if (!engine_mask)
                goto out;

        /* Full reset needs the mutex, stop any other user trying to do so. */
        if (test_and_set_bit(I915_RESET_BACKOFF, &gt->reset.flags)) {
                wait_event(gt->reset.queue,
                           !test_bit(I915_RESET_BACKOFF, &gt->reset.flags));
                goto out; /* piggy-back on the other reset */
        }

        /* Make sure i915_reset_trylock() sees the I915_RESET_BACKOFF */
        synchronize_rcu_expedited();

        /* Prevent any other reset-engine attempt. */
        for_each_engine(engine, gt, tmp) {
                while (test_and_set_bit(I915_RESET_ENGINE + engine->id,
                                        &gt->reset.flags))
                        wait_on_bit(&gt->reset.flags,
                                    I915_RESET_ENGINE + engine->id,
                                    TASK_UNINTERRUPTIBLE);
        }

        intel_gt_reset_global(gt, engine_mask, msg);

        for_each_engine(engine, gt, tmp)
                clear_bit_unlock(I915_RESET_ENGINE + engine->id,
                                 &gt->reset.flags);
        clear_bit_unlock(I915_RESET_BACKOFF, &gt->reset.flags);
        smp_mb__after_atomic();
        wake_up_all(&gt->reset.queue);

out:
        intel_runtime_pm_put(gt->uncore->rpm, wakeref);
}

int intel_gt_reset_trylock(struct intel_gt *gt, int *srcu)
{
        might_lock(&gt->reset.backoff_srcu);
        might_sleep();

        rcu_read_lock();
        while (test_bit(I915_RESET_BACKOFF, &gt->reset.flags)) {
                rcu_read_unlock();

                if (wait_event_interruptible(gt->reset.queue,
                                             !test_bit(I915_RESET_BACKOFF,
                                                       &gt->reset.flags)))
                        return -EINTR;

                rcu_read_lock();
        }
        *srcu = srcu_read_lock(&gt->reset.backoff_srcu);
        rcu_read_unlock();

        return 0;
}

void intel_gt_reset_unlock(struct intel_gt *gt, int tag)
__releases(&gt->reset.backoff_srcu)
{
        srcu_read_unlock(&gt->reset.backoff_srcu, tag);
}

int intel_gt_terminally_wedged(struct intel_gt *gt)
{
        might_sleep();

        if (!intel_gt_is_wedged(gt))
                return 0;

        if (intel_gt_has_unrecoverable_error(gt))
                return -EIO;

        /* Reset still in progress? Maybe we will recover? */
        if (wait_event_interruptible(gt->reset.queue,
                                     !test_bit(I915_RESET_BACKOFF,
                                               &gt->reset.flags)))
                return -EINTR;

        return intel_gt_is_wedged(gt) ? -EIO : 0;
}

void intel_gt_set_wedged_on_init(struct intel_gt *gt)
{
        BUILD_BUG_ON(I915_RESET_ENGINE + I915_NUM_ENGINES >
                     I915_WEDGED_ON_INIT);
        intel_gt_set_wedged(gt);
        set_bit(I915_WEDGED_ON_INIT, &gt->reset.flags);

        /* Wedged on init is non-recoverable */
        add_taint_for_CI(gt->i915, TAINT_WARN);
}

void intel_gt_set_wedged_on_fini(struct intel_gt *gt)
{
        intel_gt_set_wedged(gt);
        set_bit(I915_WEDGED_ON_FINI, &gt->reset.flags);
        intel_gt_retire_requests(gt); /* cleanup any wedged requests */
}

void intel_gt_init_reset(struct intel_gt *gt)
{
        init_waitqueue_head(&gt->reset.queue);
        mutex_init(&gt->reset.mutex);
        init_srcu_struct(&gt->reset.backoff_srcu);

        /* no GPU until we are ready! */
        __set_bit(I915_WEDGED, &gt->reset.flags);
}

void intel_gt_fini_reset(struct intel_gt *gt)
{
        cleanup_srcu_struct(&gt->reset.backoff_srcu);
}

static void intel_wedge_me(struct work_struct *work)
{
        struct intel_wedge_me *w = container_of(work, typeof(*w), work.work);

        drm_err(&w->gt->i915->drm,
                "%s timed out, cancelling all in-flight rendering.\n",
                w->name);
        intel_gt_set_wedged(w->gt);
}

void __intel_init_wedge(struct intel_wedge_me *w,
                        struct intel_gt *gt,
                        long timeout,
                        const char *name)
{
        w->gt = gt;
        w->name = name;

        INIT_DELAYED_WORK_ONSTACK(&w->work, intel_wedge_me);
        schedule_delayed_work(&w->work, timeout);
}

void __intel_fini_wedge(struct intel_wedge_me *w)
{
        cancel_delayed_work_sync(&w->work);
        destroy_delayed_work_on_stack(&w->work);
        w->gt = NULL;
}

#if IS_ENABLED(CONFIG_DRM_I915_SELFTEST)
#include "selftest_reset.c"
#include "selftest_hangcheck.c"
#endif