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>

1 files changed, 33 insertions, 0 deletions

diff --git a/drivers/gpu/drm/vc4/vc4_v3d.c b/drivers/gpu/drm/vc4/vc4_v3d.c
index e1e728e95562..b2b974f20e23 100644
--- a/drivers/gpu/drm/vc4/vc4_v3d.c
+++ b/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);