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      1 /*	$NetBSD: i915_gem_pm.c,v 1.3 2021/12/19 11:33:30 riastradh Exp $	*/
      2 
      3 /*
      4  * SPDX-License-Identifier: MIT
      5  *
      6  * Copyright  2019 Intel Corporation
      7  */
      8 
      9 #include <sys/cdefs.h>
     10 __KERNEL_RCSID(0, "$NetBSD: i915_gem_pm.c,v 1.3 2021/12/19 11:33:30 riastradh Exp $");
     11 
     12 #include "gem/i915_gem_pm.h"
     13 #include "gt/intel_gt.h"
     14 #include "gt/intel_gt_pm.h"
     15 #include "gt/intel_gt_requests.h"
     16 
     17 #include "i915_drv.h"
     18 
     19 #include <linux/nbsd-namespace.h>
     20 
     21 void i915_gem_suspend(struct drm_i915_private *i915)
     22 {
     23 	GEM_TRACE("%s\n", dev_name(i915->drm.dev));
     24 
     25 	intel_wakeref_auto(&i915->ggtt.userfault_wakeref, 0);
     26 	flush_workqueue(i915->wq);
     27 
     28 	/*
     29 	 * We have to flush all the executing contexts to main memory so
     30 	 * that they can saved in the hibernation image. To ensure the last
     31 	 * context image is coherent, we have to switch away from it. That
     32 	 * leaves the i915->kernel_context still active when
     33 	 * we actually suspend, and its image in memory may not match the GPU
     34 	 * state. Fortunately, the kernel_context is disposable and we do
     35 	 * not rely on its state.
     36 	 */
     37 	intel_gt_suspend_prepare(&i915->gt);
     38 
     39 	i915_gem_drain_freed_objects(i915);
     40 }
     41 
     42 static struct drm_i915_gem_object *first_mm_object(struct list_head *list)
     43 {
     44 	return list_first_entry_or_null(list,
     45 					struct drm_i915_gem_object,
     46 					mm.link);
     47 }
     48 
     49 void i915_gem_suspend_late(struct drm_i915_private *i915)
     50 {
     51 	struct drm_i915_gem_object *obj;
     52 	struct list_head *phases[] = {
     53 		&i915->mm.shrink_list,
     54 		&i915->mm.purge_list,
     55 		NULL
     56 	}, **phase;
     57 	unsigned long flags;
     58 
     59 	/*
     60 	 * Neither the BIOS, ourselves or any other kernel
     61 	 * expects the system to be in execlists mode on startup,
     62 	 * so we need to reset the GPU back to legacy mode. And the only
     63 	 * known way to disable logical contexts is through a GPU reset.
     64 	 *
     65 	 * So in order to leave the system in a known default configuration,
     66 	 * always reset the GPU upon unload and suspend. Afterwards we then
     67 	 * clean up the GEM state tracking, flushing off the requests and
     68 	 * leaving the system in a known idle state.
     69 	 *
     70 	 * Note that is of the upmost importance that the GPU is idle and
     71 	 * all stray writes are flushed *before* we dismantle the backing
     72 	 * storage for the pinned objects.
     73 	 *
     74 	 * However, since we are uncertain that resetting the GPU on older
     75 	 * machines is a good idea, we don't - just in case it leaves the
     76 	 * machine in an unusable condition.
     77 	 */
     78 
     79 	intel_gt_suspend_late(&i915->gt);
     80 
     81 	spin_lock_irqsave(&i915->mm.obj_lock, flags);
     82 	for (phase = phases; *phase; phase++) {
     83 		LIST_HEAD(keep);
     84 
     85 		while ((obj = first_mm_object(*phase))) {
     86 			list_move_tail(&obj->mm.link, &keep);
     87 
     88 			/* Beware the background _i915_gem_free_objects */
     89 			if (!kref_get_unless_zero(&obj->base.refcount))
     90 				continue;
     91 
     92 			spin_unlock_irqrestore(&i915->mm.obj_lock, flags);
     93 
     94 			i915_gem_object_lock(obj);
     95 			WARN_ON(i915_gem_object_set_to_gtt_domain(obj, false));
     96 			i915_gem_object_unlock(obj);
     97 			i915_gem_object_put(obj);
     98 
     99 			spin_lock_irqsave(&i915->mm.obj_lock, flags);
    100 		}
    101 
    102 		list_splice_tail(&keep, *phase);
    103 	}
    104 	spin_unlock_irqrestore(&i915->mm.obj_lock, flags);
    105 }
    106 
    107 void i915_gem_resume(struct drm_i915_private *i915)
    108 {
    109 	GEM_TRACE("%s\n", dev_name(i915->drm.dev));
    110 
    111 	/*
    112 	 * As we didn't flush the kernel context before suspend, we cannot
    113 	 * guarantee that the context image is complete. So let's just reset
    114 	 * it and start again.
    115 	 */
    116 	intel_gt_resume(&i915->gt);
    117 }
    118