[PATCH 2/4] Revert "drm/i915/gem: Almagamate clflushes on suspend"

[Michael Cheng <michael.cheng@xxxxxxxxx>]

As we are making i915 more architecture-neutral, lets revert this commit
to the previous logic [1] to avoid using wbinvd_on_all_cpus.

[1]. ac05a22cd07a ("drm/i915/gem: Almagamate clflushes on suspend")

Suggested-by: Lucas De Marchi <lucas.demarchi@xxxxxxxxx>
Signed-off-by: Michael Cheng <michael.cheng@xxxxxxxxx>
---
 drivers/gpu/drm/i915/gem/i915_gem_pm.c | 41 +++++++++++++++++---------
 1 file changed, 27 insertions(+), 14 deletions(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_pm.c b/drivers/gpu/drm/i915/gem/i915_gem_pm.c
index 00359ec9d58b..3f20961bb59b 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_pm.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_pm.c
@@ -13,13 +13,6 @@
 #include "i915_driver.h"
 #include "i915_drv.h"
 
-#if defined(CONFIG_X86)
-#include <asm/smp.h>
-#else
-#define wbinvd_on_all_cpus() \
-	pr_warn(DRIVER_NAME ": Missing cache flush in %s\n", __func__)
-#endif
-
 void i915_gem_suspend(struct drm_i915_private *i915)
 {
 	GEM_TRACE("%s\n", dev_name(i915->drm.dev));
@@ -123,6 +116,13 @@ int i915_gem_backup_suspend(struct drm_i915_private *i915)
 	return ret;
 }
 
+static struct drm_i915_gem_object *first_mm_object(struct list_head *list)
+{
+	return list_first_entry_or_null(list,
+					struct drm_i915_gem_object,
+					mm.link);
+}
+
 void i915_gem_suspend_late(struct drm_i915_private *i915)
 {
 	struct drm_i915_gem_object *obj;
@@ -132,7 +132,6 @@ void i915_gem_suspend_late(struct drm_i915_private *i915)
 		NULL
 	}, **phase;
 	unsigned long flags;
-	bool flush = false;
 
 	/*
 	 * Neither the BIOS, ourselves or any other kernel
@@ -158,15 +157,29 @@ void i915_gem_suspend_late(struct drm_i915_private *i915)
 
 	spin_lock_irqsave(&i915->mm.obj_lock, flags);
 	for (phase = phases; *phase; phase++) {
-		list_for_each_entry(obj, *phase, mm.link) {
-			if (!(obj->cache_coherent & I915_BO_CACHE_COHERENT_FOR_READ))
-				flush |= (obj->read_domains & I915_GEM_DOMAIN_CPU) == 0;
-			__start_cpu_write(obj); /* presume auto-hibernate */
+		LIST_HEAD(keep);
+
+		while ((obj = first_mm_object(*phase))) {
+			list_move_tail(&obj->mm.link, &keep);
+
+			/* Beware the background _i915_gem_free_objects */
+			if (!kref_get_unless_zero(&obj->base.refcount))
+				continue;
+
+			spin_unlock_irqrestore(&i915->mm.obj_lock, flags);
+
+			i915_gem_object_lock(obj, NULL);
+			drm_WARN_ON(&i915->drm,
+			    i915_gem_object_set_to_gtt_domain(obj, false));
+			i915_gem_object_unlock(obj);
+			i915_gem_object_put(obj);
+
+			spin_lock_irqsave(&i915->mm.obj_lock, flags);
 		}
+
+		list_splice_tail(&keep, *phase);
 	}
 	spin_unlock_irqrestore(&i915->mm.obj_lock, flags);
-	if (flush)
-		wbinvd_on_all_cpus();
 }
 
 int i915_gem_freeze(struct drm_i915_private *i915)
-- 
2.25.1