drm/i915/gvt: use hrtimer replace delayed_work in scheduler

Currently the scheduler is triggered by delayed_work, which doesn't
provide precision at microsecond level. Move to hrtimer instead for
more accurate control.

Signed-off-by: Ping Gao <ping.a.gao@intel.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>

4 files changed, 41 insertions, 16 deletions

diff --git a/drivers/gpu/drm/i915/gvt/gvt.c b/drivers/gpu/drm/i915/gvt/gvt.c
index b84b7ca3f66f..894735c77f63 100644
--- a/drivers/gpu/drm/i915/gvt/gvt.c
+++ b/drivers/gpu/drm/i915/gvt/gvt.c
@@ -144,6 +144,11 @@ static int gvt_service_thread(void *data)
                         intel_gvt_emulate_vblank(gvt);
                         mutex_unlock(&gvt->lock);
                 }
+
+                if (test_and_clear_bit(INTEL_GVT_REQUEST_SCHED,
+                                        (void *)&gvt->service_request)) {
+                        intel_gvt_schedule(gvt);
+                }
         }
 
         return 0;
diff --git a/drivers/gpu/drm/i915/gvt/gvt.h b/drivers/gpu/drm/i915/gvt/gvt.h
index 6dfc48b63b71..7455214b242c 100644
--- a/drivers/gpu/drm/i915/gvt/gvt.h
+++ b/drivers/gpu/drm/i915/gvt/gvt.h
@@ -249,6 +249,7 @@ static inline struct intel_gvt *to_gvt(struct drm_i915_private *i915)
 
 enum {
         INTEL_GVT_REQUEST_EMULATE_VBLANK = 0,
+        INTEL_GVT_REQUEST_SCHED = 1,
 };
 
 static inline void intel_gvt_request_service(struct intel_gvt *gvt,
diff --git a/drivers/gpu/drm/i915/gvt/sched_policy.c b/drivers/gpu/drm/i915/gvt/sched_policy.c
index 34b9acdf3479..c8ade8fc511d 100644
--- a/drivers/gpu/drm/i915/gvt/sched_policy.c
+++ b/drivers/gpu/drm/i915/gvt/sched_policy.c
@@ -96,17 +96,16 @@ struct tbs_vgpu_data {
 
 struct tbs_sched_data {
         struct intel_gvt *gvt;
-        struct delayed_work work;
+        struct hrtimer timer;
         unsigned long period;
         struct list_head runq_head;
 };
 
-#define GVT_DEFAULT_TIME_SLICE (msecs_to_jiffies(1))
+/* in nanosecond */
+#define GVT_DEFAULT_TIME_SLICE 1000000
 
-static void tbs_sched_func(struct work_struct *work)
+static void tbs_sched_func(struct tbs_sched_data *sched_data)
 {
-        struct tbs_sched_data *sched_data = container_of(work,
-                        struct tbs_sched_data, work.work);
         struct tbs_vgpu_data *vgpu_data;
 
         struct intel_gvt *gvt = sched_data->gvt;
@@ -115,8 +114,6 @@ static void tbs_sched_func(struct work_struct *work)
         struct intel_vgpu *vgpu = NULL;
         struct list_head *pos, *head;
 
-        mutex_lock(&gvt->lock);
-
         /* no vgpu or has already had a target */
         if (list_empty(&sched_data->runq_head) || scheduler->next_vgpu)
                 goto out;
@@ -151,17 +148,30 @@ out:
                                 scheduler->next_vgpu->id);
                 try_to_schedule_next_vgpu(gvt);
         }
+}
 
-        /*
-         * still have vgpu on runq
-         * or last schedule haven't finished due to running workload
-         */
-        if (!list_empty(&sched_data->runq_head) || scheduler->next_vgpu)
-                schedule_delayed_work(&sched_data->work, sched_data->period);
+void intel_gvt_schedule(struct intel_gvt *gvt)
+{
+        struct tbs_sched_data *sched_data = gvt->scheduler.sched_data;
 
+        mutex_lock(&gvt->lock);
+        tbs_sched_func(sched_data);
         mutex_unlock(&gvt->lock);
 }
 
+static enum hrtimer_restart tbs_timer_fn(struct hrtimer *timer_data)
+{
+        struct tbs_sched_data *data;
+
+        data = container_of(timer_data, struct tbs_sched_data, timer);
+
+        intel_gvt_request_service(data->gvt, INTEL_GVT_REQUEST_SCHED);
+
+        hrtimer_add_expires_ns(&data->timer, data->period);
+
+        return HRTIMER_RESTART;
+}
+
 static int tbs_sched_init(struct intel_gvt *gvt)
 {
         struct intel_gvt_workload_scheduler *scheduler =
@@ -174,11 +184,13 @@ static int tbs_sched_init(struct intel_gvt *gvt)
                 return -ENOMEM;
 
         INIT_LIST_HEAD(&data->runq_head);
-        INIT_DELAYED_WORK(&data->work, tbs_sched_func);
+        hrtimer_init(&data->timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
+        data->timer.function = tbs_timer_fn;
         data->period = GVT_DEFAULT_TIME_SLICE;
         data->gvt = gvt;
 
         scheduler->sched_data = data;
+
         return 0;
 }
 
@@ -188,7 +200,8 @@ static void tbs_sched_clean(struct intel_gvt *gvt)
                 &gvt->scheduler;
         struct tbs_sched_data *data = scheduler->sched_data;
 
-        cancel_delayed_work(&data->work);
+        hrtimer_cancel(&data->timer);
+
         kfree(data);
         scheduler->sched_data = NULL;
 }
@@ -205,6 +218,7 @@ static int tbs_sched_init_vgpu(struct intel_vgpu *vgpu)
         INIT_LIST_HEAD(&data->list);
 
         vgpu->sched_data = data;
+
         return 0;
 }
 
@@ -223,7 +237,10 @@ static void tbs_sched_start_schedule(struct intel_vgpu *vgpu)
                 return;
 
         list_add_tail(&vgpu_data->list, &sched_data->runq_head);
-        schedule_delayed_work(&sched_data->work, 0);
+
+        if (!hrtimer_active(&sched_data->timer))
+                hrtimer_start(&sched_data->timer, ktime_add_ns(ktime_get(),
+                        sched_data->period), HRTIMER_MODE_ABS);
 }
 
 static void tbs_sched_stop_schedule(struct intel_vgpu *vgpu)
diff --git a/drivers/gpu/drm/i915/gvt/sched_policy.h b/drivers/gpu/drm/i915/gvt/sched_policy.h
index bb8b9097e41a..ba00a5f7455f 100644
--- a/drivers/gpu/drm/i915/gvt/sched_policy.h
+++ b/drivers/gpu/drm/i915/gvt/sched_policy.h
@@ -43,6 +43,8 @@ struct intel_gvt_sched_policy_ops {
         void (*stop_schedule)(struct intel_vgpu *vgpu);
 };
 
+void intel_gvt_schedule(struct intel_gvt *gvt);
+
 int intel_gvt_init_sched_policy(struct intel_gvt *gvt);
 
 void intel_gvt_clean_sched_policy(struct intel_gvt *gvt);