linux-kernel - [PATCH 4.9 02/24] drm/vc4: Use runtime autosuspend to avoid thrashing V3D power state.

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Message-Id: <20170324151225.483997022@linuxfoundation.org>
Date:   Fri, 24 Mar 2017 18:58:35 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Eric Anholt <eric@...olt.net>,
        Amit Pundir <amit.pundir@...aro.org>
Subject: [PATCH 4.9 02/24] drm/vc4: Use runtime autosuspend to avoid thrashing V3D power state.

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Eric Anholt <eric@...olt.net>

commit 3a62234680d86efa0239665ed8a0e908f1aef147 upstream.

The pm_runtime_put() we were using immediately released power on the
device, which meant that we were generally turning the device off and
on once per frame.  In many profiles I've looked at, that added up to
about 1% of CPU time, but this could get worse in the case of frequent
rendering and readback (as may happen in X rendering).  By keeping the
device on until we've been idle for a couple of frames, we drop the
overhead of runtime PM down to sub-.1%.

Signed-off-by: Eric Anholt <eric@...olt.net>
Cc: Amit Pundir <amit.pundir@...aro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/gpu/drm/vc4/vc4_drv.c |    9 ++++++---
 drivers/gpu/drm/vc4/vc4_gem.c |    6 ++++--
 drivers/gpu/drm/vc4/vc4_v3d.c |    2 ++
 3 files changed, 12 insertions(+), 5 deletions(-)

--- a/drivers/gpu/drm/vc4/vc4_drv.c
+++ b/drivers/gpu/drm/vc4/vc4_drv.c
@@ -61,21 +61,24 @@ static int vc4_get_param_ioctl(struct dr
 		if (ret < 0)
 			return ret;
 		args->value = V3D_READ(V3D_IDENT0);
-		pm_runtime_put(&vc4->v3d->pdev->dev);
+		pm_runtime_mark_last_busy(&vc4->v3d->pdev->dev);
+		pm_runtime_put_autosuspend(&vc4->v3d->pdev->dev);
 		break;
 	case DRM_VC4_PARAM_V3D_IDENT1:
 		ret = pm_runtime_get_sync(&vc4->v3d->pdev->dev);
 		if (ret < 0)
 			return ret;
 		args->value = V3D_READ(V3D_IDENT1);
-		pm_runtime_put(&vc4->v3d->pdev->dev);
+		pm_runtime_mark_last_busy(&vc4->v3d->pdev->dev);
+		pm_runtime_put_autosuspend(&vc4->v3d->pdev->dev);
 		break;
 	case DRM_VC4_PARAM_V3D_IDENT2:
 		ret = pm_runtime_get_sync(&vc4->v3d->pdev->dev);
 		if (ret < 0)
 			return ret;
 		args->value = V3D_READ(V3D_IDENT2);
-		pm_runtime_put(&vc4->v3d->pdev->dev);
+		pm_runtime_mark_last_busy(&vc4->v3d->pdev->dev);
+		pm_runtime_put_autosuspend(&vc4->v3d->pdev->dev);
 		break;
 	case DRM_VC4_PARAM_SUPPORTS_BRANCHES:
 		args->value = true;
--- a/drivers/gpu/drm/vc4/vc4_gem.c
+++ b/drivers/gpu/drm/vc4/vc4_gem.c
@@ -711,8 +711,10 @@ vc4_complete_exec(struct drm_device *dev
 	}
 
 	mutex_lock(&vc4->power_lock);
-	if (--vc4->power_refcount == 0)
-		pm_runtime_put(&vc4->v3d->pdev->dev);
+	if (--vc4->power_refcount == 0) {
+		pm_runtime_mark_last_busy(&vc4->v3d->pdev->dev);
+		pm_runtime_put_autosuspend(&vc4->v3d->pdev->dev);
+	}
 	mutex_unlock(&vc4->power_lock);
 
 	kfree(exec);
--- a/drivers/gpu/drm/vc4/vc4_v3d.c
+++ b/drivers/gpu/drm/vc4/vc4_v3d.c
@@ -222,6 +222,8 @@ static int vc4_v3d_bind(struct device *d
 		return ret;
 	}
 
+	pm_runtime_use_autosuspend(dev);
+	pm_runtime_set_autosuspend_delay(dev, 40); /* a little over 2 frames. */
 	pm_runtime_enable(dev);
 
 	return 0;