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1/*2 * SPDX-License-Identifier: MIT3 *4 * Copyright © 2014-2016 Intel Corporation5 */6 7#include <linux/jiffies.h>8 9#include <drm/drm_file.h>10 11#include "i915_drv.h"12#include "i915_file_private.h"13#include "i915_gem_context.h"14#include "i915_gem_ioctls.h"15#include "i915_gem_object.h"16 17/*18 * 20ms is a fairly arbitrary limit (greater than the average frame time)19 * chosen to prevent the CPU getting more than a frame ahead of the GPU20 * (when using lax throttling for the frontbuffer). We also use it to21 * offer free GPU waitboosts for severely congested workloads.22 */23#define DRM_I915_THROTTLE_JIFFIES msecs_to_jiffies(20)24 25/*26 * Throttle our rendering by waiting until the ring has completed our requests27 * emitted over 20 msec ago.28 *29 * Note that if we were to use the current jiffies each time around the loop,30 * we wouldn't escape the function with any frames outstanding if the time to31 * render a frame was over 20ms.32 *33 * This should get us reasonable parallelism between CPU and GPU but also34 * relatively low latency when blocking on a particular request to finish.35 */36int37i915_gem_throttle_ioctl(struct drm_device *dev, void *data,38 struct drm_file *file)39{40 const unsigned long recent_enough = jiffies - DRM_I915_THROTTLE_JIFFIES;41 struct drm_i915_file_private *file_priv = file->driver_priv;42 struct drm_i915_private *i915 = to_i915(dev);43 struct i915_gem_context *ctx;44 unsigned long idx;45 long ret;46 47 /* ABI: return -EIO if already wedged */48 ret = intel_gt_terminally_wedged(to_gt(i915));49 if (ret)50 return ret;51 52 rcu_read_lock();53 xa_for_each(&file_priv->context_xa, idx, ctx) {54 struct i915_gem_engines_iter it;55 struct intel_context *ce;56 57 if (!kref_get_unless_zero(&ctx->ref))58 continue;59 rcu_read_unlock();60 61 for_each_gem_engine(ce,62 i915_gem_context_lock_engines(ctx),63 it) {64 struct i915_request *rq, *target = NULL;65 66 if (!ce->timeline)67 continue;68 69 mutex_lock(&ce->timeline->mutex);70 list_for_each_entry_reverse(rq,71 &ce->timeline->requests,72 link) {73 if (i915_request_completed(rq))74 break;75 76 if (time_after(rq->emitted_jiffies,77 recent_enough))78 continue;79 80 target = i915_request_get(rq);81 break;82 }83 mutex_unlock(&ce->timeline->mutex);84 if (!target)85 continue;86 87 ret = i915_request_wait(target,88 I915_WAIT_INTERRUPTIBLE,89 MAX_SCHEDULE_TIMEOUT);90 i915_request_put(target);91 if (ret < 0)92 break;93 }94 i915_gem_context_unlock_engines(ctx);95 i915_gem_context_put(ctx);96 97 rcu_read_lock();98 }99 rcu_read_unlock();100 101 return ret < 0 ? ret : 0;102}103