drm/msm/devfreq: Add 1ms delay before clamping freq

Add a short delay before clamping to idle frequency on active->idle
transition.  It takes ~0.5ms to increase the freq again on the next
idle->active transition, so this helps avoid extra freq transitions
on workloads that bounce between CPU and GPU.

Signed-off-by: Rob Clark <robdclark@chromium.org>
Link: https://lore.kernel.org/r/20210927230455.1066297-2-robdclark@gmail.com
Signed-off-by: Rob Clark <robdclark@chromium.org>

diff --git a/drivers/gpu/drm/msm/msm_gpu.h b/drivers/gpu/drm/msm/msm_gpu.h
index 030f82f..5987009 100644 (file)
--- a/drivers/gpu/drm/msm/msm_gpu.h
+++ b/drivers/gpu/drm/msm/msm_gpu.h
@@ -112,6 +112,13 @@ struct msm_gpu_devfreq {
         * it is inactive.
         */
        unsigned long idle_freq;
+
+       /**
+        * idle_work:
+        *
+        * Used to delay clamping to idle freq on active->idle transition.
+        */
+       struct msm_hrtimer_work idle_work;
 };
 
 struct msm_gpu {

diff --git a/drivers/gpu/drm/msm/msm_gpu_devfreq.c b/drivers/gpu/drm/msm/msm_gpu_devfreq.c
index 84e98c0..d32b729 100644 (file)
--- a/drivers/gpu/drm/msm/msm_gpu_devfreq.c
+++ b/drivers/gpu/drm/msm/msm_gpu_devfreq.c
@@ -88,8 +88,12 @@ static struct devfreq_dev_profile msm_devfreq_profile = {
        .get_cur_freq = msm_devfreq_get_cur_freq,
 };
 
+static void msm_devfreq_idle_work(struct kthread_work *work);
+
 void msm_devfreq_init(struct msm_gpu *gpu)
 {
+       struct msm_gpu_devfreq *df = &gpu->devfreq;
+
        /* We need target support to do devfreq */
        if (!gpu->funcs->gpu_busy)
                return;
@@ -105,25 +109,27 @@ void msm_devfreq_init(struct msm_gpu *gpu)
        msm_devfreq_profile.freq_table = NULL;
        msm_devfreq_profile.max_state = 0;
 
-       gpu->devfreq.devfreq = devm_devfreq_add_device(&gpu->pdev->dev,
+       df->devfreq = devm_devfreq_add_device(&gpu->pdev->dev,
                        &msm_devfreq_profile, DEVFREQ_GOV_SIMPLE_ONDEMAND,
                        NULL);
 
-       if (IS_ERR(gpu->devfreq.devfreq)) {
+       if (IS_ERR(df->devfreq)) {
                DRM_DEV_ERROR(&gpu->pdev->dev, "Couldn't initialize GPU devfreq\n");
-               gpu->devfreq.devfreq = NULL;
+               df->devfreq = NULL;
                return;
        }
 
-       devfreq_suspend_device(gpu->devfreq.devfreq);
+       devfreq_suspend_device(df->devfreq);
 
-       gpu->cooling = of_devfreq_cooling_register(gpu->pdev->dev.of_node,
-                       gpu->devfreq.devfreq);
+       gpu->cooling = of_devfreq_cooling_register(gpu->pdev->dev.of_node, df->devfreq);
        if (IS_ERR(gpu->cooling)) {
                DRM_DEV_ERROR(&gpu->pdev->dev,
                                "Couldn't register GPU cooling device\n");
                gpu->cooling = NULL;
        }
+
+       msm_hrtimer_work_init(&df->idle_work, gpu->worker, msm_devfreq_idle_work,
+                             CLOCK_MONOTONIC, HRTIMER_MODE_REL);
 }
 
 void msm_devfreq_cleanup(struct msm_gpu *gpu)
@@ -155,6 +161,11 @@ void msm_devfreq_active(struct msm_gpu *gpu)
                return;
 
        /*
+        * Cancel any pending transition to idle frequency:
+        */
+       hrtimer_cancel(&df->idle_work.timer);
+
+       /*
         * Hold devfreq lock to synchronize with get_dev_status()/
         * target() callbacks
         */
@@ -184,9 +195,12 @@ void msm_devfreq_active(struct msm_gpu *gpu)
        mutex_unlock(&df->devfreq->lock);
 }
 
-void msm_devfreq_idle(struct msm_gpu *gpu)
+
+static void msm_devfreq_idle_work(struct kthread_work *work)
 {
-       struct msm_gpu_devfreq *df = &gpu->devfreq;
+       struct msm_gpu_devfreq *df = container_of(work,
+                       struct msm_gpu_devfreq, idle_work.work);
+       struct msm_gpu *gpu = container_of(df, struct msm_gpu, devfreq);
        unsigned long idle_freq, target_freq = 0;
 
        if (!df->devfreq)
@@ -207,3 +221,11 @@ void msm_devfreq_idle(struct msm_gpu *gpu)
 
        mutex_unlock(&df->devfreq->lock);
 }
+
+void msm_devfreq_idle(struct msm_gpu *gpu)
+{
+       struct msm_gpu_devfreq *df = &gpu->devfreq;
+
+       msm_hrtimer_queue_work(&df->idle_work, ms_to_ktime(1),
+                              HRTIMER_MODE_ABS);
+}