[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 <dig...@gmail.com>
---
 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