[PATCH 4/6] drm/exynos: g2d: wait for engine to finish

[Tobias Jakobi]

While the engine works on a runqueue node it does memory access to
the buffers associated with that node.
Make sure that the engine is idle when g2d_close() and/or
g2d_remove() are called, i.e. buffer associated with the process (for
g2d_close()), or all buffers (for g2d_remove()) can be safely be
unmapped.

We have to take into account that the engine might be in an undefined
state, i.e. it hangs and doesn't become idle. In this case, we issue
a hardware reset to return the hardware and the driver context into a
proper state.

Signed-off-by: Tobias Jakobi <tjakobi at math.uni-bielefeld.de>
---
 drivers/gpu/drm/exynos/exynos_drm_g2d.c | 84 ++++++++++++++++++++++++++++++---
 1 file changed, 77 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/exynos/exynos_drm_g2d.c b/drivers/gpu/drm/exynos/exynos_drm_g2d.c
index 3599489..5de5ea4 100644
--- a/drivers/gpu/drm/exynos/exynos_drm_g2d.c
+++ b/drivers/gpu/drm/exynos/exynos_drm_g2d.c
@@ -258,6 +258,12 @@ struct g2d_data {
 	unsigned long			max_pool;
 };
 
+static inline void g2d_hw_reset(struct g2d_data *g2d)
+{
+	writel(G2D_R | G2D_SFRCLEAR, g2d->regs + G2D_SOFT_RESET);
+	clear_bit(G2D_BIT_ENGINE_BUSY, &g2d->flags);
+}
+
 static int g2d_init_cmdlist(struct g2d_data *g2d)
 {
 	struct device *dev = g2d->dev;
@@ -969,6 +975,63 @@ static irqreturn_t g2d_irq_handler(int irq, void *dev_id)
 	return IRQ_HANDLED;
 }
 
+/**
+ * g2d_wait_finish - wait for the G2D engine to finish the current runqueue node
+ * @g2d: G2D state object
+ * @file: if not zero, only wait if the current runqueue node belongs
+ *        to the DRM file
+ *
+ * Should the engine not become idle after a 100ms timeout, a hardware
+ * reset is issued.
+ */
+static void g2d_wait_finish(struct g2d_data *g2d, struct drm_file *file)
+{
+	struct device *dev = g2d->dev;
+
+	struct g2d_runqueue_node *runqueue_node = NULL;
+	unsigned int tries = 10;
+
+	mutex_lock(&g2d->runqueue_mutex);
+
+	/* If no node is currently processed, we have nothing to do. */
+	if (!g2d->runqueue_node)
+		goto out;
+
+	runqueue_node = g2d->runqueue_node;
+
+	/* Check if the currently processed item belongs to us. */
+	if (file && runqueue_node->filp != file)
+		goto out;
+
+	mutex_unlock(&g2d->runqueue_mutex);
+
+	/* Wait for the G2D engine to finish. */
+	while (tries-- && (g2d->runqueue_node == runqueue_node))
+		mdelay(10);
+
+	mutex_lock(&g2d->runqueue_mutex);
+
+	if (g2d->runqueue_node != runqueue_node)
+		goto out;
+
+	dev_err(dev, "wait timed out, resetting engine...\n");
+	g2d_hw_reset(g2d);
+
+	/*
+	 * After the hardware reset of the engine we are going to loose
+	 * the IRQ which triggers the PM runtime put().
+	 * So do this manually here.
+	 */
+	pm_runtime_put(dev);
+
+	complete(&runqueue_node->complete);
+	if (runqueue_node->async)
+		g2d_free_runqueue_node(g2d, runqueue_node);
+
+out:
+	mutex_unlock(&g2d->runqueue_mutex);
+}
+
 static int g2d_check_reg_offset(struct device *dev,
 				struct g2d_cmdlist_node *node,
 				int nr, bool for_addr)
@@ -1391,6 +1454,13 @@ static void g2d_close(struct drm_device *drm_dev, struct device *dev,
 	mutex_unlock(&g2d->runqueue_mutex);
 
 	/*
+	 * Wait for the runqueue worker to finish its current node.
+	 * After this the engine should no longer be accessing any
+	 * memory belonging to us.
+	 */
+	g2d_wait_finish(g2d, file);
+
+	/*
 	 * Even after the engine is idle, there might still be stale cmdlists
 	 * (i.e. cmdlisst which we submitted but never executed) around, with
 	 * their corresponding GEM/userptr buffers.
@@ -1510,8 +1580,9 @@ static int g2d_remove(struct platform_device *pdev)
 {
 	struct g2d_data *g2d = platform_get_drvdata(pdev);
 
-	/* Suspend runqueue operation. */
+	/* Suspend operation and wait for engine idle. */
 	set_bit(G2D_BIT_SUSPEND_RUNQUEUE, &g2d->flags);
+	g2d_wait_finish(g2d, NULL);
 
 	cancel_work_sync(&g2d->runqueue_work);
 	exynos_drm_subdrv_unregister(&g2d->subdrv);
@@ -1533,13 +1604,12 @@ static int g2d_suspend(struct device *dev)
 {
 	struct g2d_data *g2d = dev_get_drvdata(dev);
 
-	/* Suspend runqueue operation. */
+	/*
+	 * Suspend the runqueue worker operation and wait until the G2D
+	 * engine is idle.
+	 */
 	set_bit(G2D_BIT_SUSPEND_RUNQUEUE, &g2d->flags);
-
-	while (g2d->runqueue_node)
-		/* FIXME: good range? */
-		usleep_range(500, 1000);
-
+	g2d_wait_finish(g2d, NULL);
 	flush_work(&g2d->runqueue_work);
 
 	return 0;
-- 
2.7.3