drm/vc4: Add helpers for pm get/put.

This makes sure the vc4_reset doesn't hit an obscure race with the
GET_PARAM ioctl, fixes a decrement outside of the lock, and prevents
future code from making mistakes with the weird return value of
pm_runtime_get_sync().

Signed-off-by: Eric Anholt <eric@anholt.net>
Link: https://patchwork.freedesktop.org/patch/msgid/20190220210343.28157-6-eric@anholt.net
Reviewed-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>

drivers/gpu/drm/vc4/vc4_drv.c

@@ -74,28 +74,25 @@ static int vc4_get_param_ioctl(struct drm_device *dev, void *data,
 
 	switch (args->param) {
 	case DRM_VC4_PARAM_V3D_IDENT0:
-		ret = pm_runtime_get_sync(&vc4->v3d->pdev->dev);
-		if (ret < 0)
+		ret = vc4_v3d_pm_get(vc4);
+		if (ret)
 			return ret;
 		args->value = V3D_READ(V3D_IDENT0);
-		pm_runtime_mark_last_busy(&vc4->v3d->pdev->dev);
-		pm_runtime_put_autosuspend(&vc4->v3d->pdev->dev);
+		vc4_v3d_pm_put(vc4);
 		break;
 	case DRM_VC4_PARAM_V3D_IDENT1:
-		ret = pm_runtime_get_sync(&vc4->v3d->pdev->dev);
-		if (ret < 0)
+		ret = vc4_v3d_pm_get(vc4);
+		if (ret)
 			return ret;
 		args->value = V3D_READ(V3D_IDENT1);
-		pm_runtime_mark_last_busy(&vc4->v3d->pdev->dev);
-		pm_runtime_put_autosuspend(&vc4->v3d->pdev->dev);
+		vc4_v3d_pm_put(vc4);
 		break;
 	case DRM_VC4_PARAM_V3D_IDENT2:
-		ret = pm_runtime_get_sync(&vc4->v3d->pdev->dev);
-		if (ret < 0)
+		ret = vc4_v3d_pm_get(vc4);
+		if (ret)
 			return ret;
 		args->value = V3D_READ(V3D_IDENT2);
-		pm_runtime_mark_last_busy(&vc4->v3d->pdev->dev);
-		pm_runtime_put_autosuspend(&vc4->v3d->pdev->dev);
+		vc4_v3d_pm_put(vc4);
 		break;
 	case DRM_VC4_PARAM_SUPPORTS_BRANCHES:
 	case DRM_VC4_PARAM_SUPPORTS_ETC1:

drivers/gpu/drm/vc4/vc4_drv.h

@@ -815,6 +815,8 @@ extern struct platform_driver vc4_v3d_driver;
 int vc4_v3d_debugfs_ident(struct seq_file *m, void *unused);
 int vc4_v3d_debugfs_regs(struct seq_file *m, void *unused);
 int vc4_v3d_get_bin_slot(struct vc4_dev *vc4);
+int vc4_v3d_pm_get(struct vc4_dev *vc4);
+void vc4_v3d_pm_put(struct vc4_dev *vc4);
 
 /* vc4_validate.c */
 int

drivers/gpu/drm/vc4/vc4_gem.c

@@ -964,12 +964,7 @@ vc4_complete_exec(struct drm_device *dev, struct vc4_exec_info *exec)
 	/* Release the reference we had on the perf monitor. */
 	vc4_perfmon_put(exec->perfmon);
 
-	mutex_lock(&vc4->power_lock);
-	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);
+	vc4_v3d_pm_put(vc4);
 
 	kfree(exec);
 }
@@ -1143,17 +1138,11 @@ vc4_submit_cl_ioctl(struct drm_device *dev, void *data,
 		return -ENOMEM;
 	}
 
-	mutex_lock(&vc4->power_lock);
-	if (vc4->power_refcount++ == 0) {
-		ret = pm_runtime_get_sync(&vc4->v3d->pdev->dev);
-		if (ret < 0) {
-			mutex_unlock(&vc4->power_lock);
-			vc4->power_refcount--;
-			kfree(exec);
-			return ret;
-		}
+	ret = vc4_v3d_pm_get(vc4);
+	if (ret) {
+		kfree(exec);
+		return ret;
 	}
-	mutex_unlock(&vc4->power_lock);
 
 	exec->args = args;
 	INIT_LIST_HEAD(&exec->unref_list);

drivers/gpu/drm/vc4/vc4_v3d.c

@@ -138,6 +138,39 @@ int vc4_v3d_debugfs_ident(struct seq_file *m, void *unused)
 }
 #endif /* CONFIG_DEBUG_FS */
 
+/**
+ * Wraps pm_runtime_get_sync() in a refcount, so that we can reliably
+ * get the pm_runtime refcount to 0 in vc4_reset().
+ */
+int
+vc4_v3d_pm_get(struct vc4_dev *vc4)
+{
+	mutex_lock(&vc4->power_lock);
+	if (vc4->power_refcount++ == 0) {
+		int ret = pm_runtime_get_sync(&vc4->v3d->pdev->dev);
+
+		if (ret < 0) {
+			vc4->power_refcount--;
+			mutex_unlock(&vc4->power_lock);
+			return ret;
+		}
+	}
+	mutex_unlock(&vc4->power_lock);
+
+	return 0;
+}
+
+void
+vc4_v3d_pm_put(struct vc4_dev *vc4)
+{
+	mutex_lock(&vc4->power_lock);
+	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);
+}
+
 static void vc4_v3d_init_hw(struct drm_device *dev)
 {
 	struct vc4_dev *vc4 = to_vc4_dev(dev);