[PATCH v1] media: staging: tegra-vde: Reset memory client

[Dmitry Osipenko]

DMA requests must be blocked before resetting VDE HW, otherwise it is
possible to get a memory corruption or a machine hang. Use the reset
control provided by the Memory Controller to block DMA before resetting
the VDE HW.

Signed-off-by: Dmitry Osipenko <digetx@xxxxxxxxx>
---
 drivers/staging/media/tegra-vde/tegra-vde.c | 42 +++++++++++++++++++--
 1 file changed, 38 insertions(+), 4 deletions(-)

diff --git a/drivers/staging/media/tegra-vde/tegra-vde.c b/drivers/staging/media/tegra-vde/tegra-vde.c
index 90177a59b97c..6dd3bf4481be 100644
--- a/drivers/staging/media/tegra-vde/tegra-vde.c
+++ b/drivers/staging/media/tegra-vde/tegra-vde.c
@@ -73,6 +73,7 @@ struct tegra_vde {
 	struct mutex lock;
 	struct miscdevice miscdev;
 	struct reset_control *rst;
+	struct reset_control *rst_mc;
 	struct gen_pool *iram_pool;
 	struct completion decode_completion;
 	struct clk *clk;
@@ -850,9 +851,23 @@ static int tegra_vde_ioctl_decode_h264(struct tegra_vde *vde,
 	 * We rely on the VDE registers reset value, otherwise VDE
 	 * causes bus lockup.
 	 */
+	ret = reset_control_assert(vde->rst_mc);
+	if (ret) {
+		dev_err(dev, "DEC start: Failed to assert MC reset: %d\n",
+			ret);
+		goto put_runtime_pm;
+	}
+
 	ret = reset_control_reset(vde->rst);
 	if (ret) {
-		dev_err(dev, "Failed to reset HW: %d\n", ret);
+		dev_err(dev, "DEC start: Failed to reset HW: %d\n", ret);
+		goto put_runtime_pm;
+	}
+
+	ret = reset_control_deassert(vde->rst_mc);
+	if (ret) {
+		dev_err(dev, "DEC start: Failed to deassert MC reset: %d\n",
+			ret);
 		goto put_runtime_pm;
 	}
 
@@ -880,9 +895,21 @@ static int tegra_vde_ioctl_decode_h264(struct tegra_vde *vde,
 		ret = timeout;
 	}
 
-	err = reset_control_assert(vde->rst);
-	if (err)
-		dev_err(dev, "Failed to assert HW reset: %d\n", err);
+	/*
+	 * At first reset memory client to avoid resetting VDE HW in the
+	 * middle of DMA which could result into memory corruption or hang
+	 * the whole system.
+	 */
+	err = reset_control_assert(vde->rst_mc);
+	if (!err) {
+		err = reset_control_assert(vde->rst);
+		if (err)
+			dev_err(dev,
+				"DEC end: Failed to assert HW reset: %d\n",
+				err);
+	} else {
+		dev_err(dev, "DEC end: Failed to assert MC reset: %d\n", err);
+	}
 
 put_runtime_pm:
 	pm_runtime_mark_last_busy(dev);
@@ -1074,6 +1101,13 @@ static int tegra_vde_probe(struct platform_device *pdev)
 		return err;
 	}
 
+	vde->rst_mc = devm_reset_control_get_optional(dev, "mc");
+	if (IS_ERR(vde->rst_mc)) {
+		err = PTR_ERR(vde->rst_mc);
+		dev_err(dev, "Could not get MC reset %d\n", err);
+		return err;
+	}
+
 	irq = platform_get_irq_byname(pdev, "sync-token");
 	if (irq < 0)
 		return irq;
-- 
2.17.0