/*
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* SPDX-License-Identifier: MIT
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*
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* Copyright © 2014-2016 Intel Corporation
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*/
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#include <linux/jiffies.h>
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#include <drm/drm_file.h>
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#include "i915_drv.h"
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#include "i915_gem_context.h"
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#include "i915_gem_ioctls.h"
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#include "i915_gem_object.h"
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/*
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* 20ms is a fairly arbitrary limit (greater than the average frame time)
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* chosen to prevent the CPU getting more than a frame ahead of the GPU
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* (when using lax throttling for the frontbuffer). We also use it to
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* offer free GPU waitboosts for severely congested workloads.
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*/
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#define DRM_I915_THROTTLE_JIFFIES msecs_to_jiffies(20)
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/*
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* Throttle our rendering by waiting until the ring has completed our requests
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* emitted over 20 msec ago.
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*
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* Note that if we were to use the current jiffies each time around the loop,
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* we wouldn't escape the function with any frames outstanding if the time to
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* render a frame was over 20ms.
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*
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* This should get us reasonable parallelism between CPU and GPU but also
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* relatively low latency when blocking on a particular request to finish.
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*/
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int
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i915_gem_throttle_ioctl(struct drm_device *dev, void *data,
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struct drm_file *file)
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{
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const unsigned long recent_enough = jiffies - DRM_I915_THROTTLE_JIFFIES;
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struct drm_i915_file_private *file_priv = file->driver_priv;
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struct i915_gem_context *ctx;
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unsigned long idx;
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long ret;
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/* ABI: return -EIO if already wedged */
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ret = intel_gt_terminally_wedged(&to_i915(dev)->gt);
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if (ret)
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return ret;
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rcu_read_lock();
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xa_for_each(&file_priv->context_xa, idx, ctx) {
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struct i915_gem_engines_iter it;
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struct intel_context *ce;
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if (!kref_get_unless_zero(&ctx->ref))
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continue;
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rcu_read_unlock();
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for_each_gem_engine(ce,
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i915_gem_context_lock_engines(ctx),
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it) {
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struct i915_request *rq, *target = NULL;
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if (!ce->timeline)
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continue;
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mutex_lock(&ce->timeline->mutex);
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list_for_each_entry_reverse(rq,
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&ce->timeline->requests,
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link) {
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if (i915_request_completed(rq))
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break;
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if (time_after(rq->emitted_jiffies,
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recent_enough))
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continue;
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target = i915_request_get(rq);
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break;
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}
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mutex_unlock(&ce->timeline->mutex);
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if (!target)
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continue;
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ret = i915_request_wait(target,
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I915_WAIT_INTERRUPTIBLE,
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MAX_SCHEDULE_TIMEOUT);
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i915_request_put(target);
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if (ret < 0)
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break;
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}
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i915_gem_context_unlock_engines(ctx);
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i915_gem_context_put(ctx);
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rcu_read_lock();
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}
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rcu_read_unlock();
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return ret < 0 ? ret : 0;
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}
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