72 lines
1.9 KiB
C
72 lines
1.9 KiB
C
/*
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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_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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struct drm_i915_file_private *file_priv = file->driver_priv;
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unsigned long recent_enough = jiffies - DRM_I915_THROTTLE_JIFFIES;
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struct i915_request *request, *target = NULL;
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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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spin_lock(&file_priv->mm.lock);
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list_for_each_entry(request, &file_priv->mm.request_list, client_link) {
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if (time_after_eq(request->emitted_jiffies, recent_enough))
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break;
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if (target && xchg(&target->file_priv, NULL))
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list_del(&target->client_link);
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target = request;
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}
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if (target)
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i915_request_get(target);
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spin_unlock(&file_priv->mm.lock);
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if (!target)
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return 0;
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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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return ret < 0 ? ret : 0;
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}
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