CHROMIUM: dmaengine: tegra-adma: Avoid tasklet from self-destructing

Fix commit 92cd07d which added code
to kill tasklet on tegra_adma_terminate_all(). But this function is
also invoked from tasklet itself resulting in forever loop. So avoid
call to tasklet_kill when called from irq context.

BUG=chrome-os-partner:46247
TEST=Launch Epic Citadel game and click on more options

Change-Id: Ic0179bdd7ace99d1a3989b43d5794a3bd550afa7
Signed-off-by: Maneet Singh <mmaneetsingh@nvidia.com>
Reviewed-on: https://chromium-review.googlesource.com/304957
Commit-Ready: Anatol Pomazau <anatol@google.com>
Tested-by: Anatol Pomazau <anatol@google.com>
Reviewed-by: Anatol Pomazau <anatol@google.com>
Reviewed-by: Andrew Bresticker <abrestic@chromium.org>

drivers/dma/tegra210-adma.c

@@ -725,13 +725,17 @@ static void tegra_adma_terminate_all(struct dma_chan *dc)
 
 	tegra_adma_resume(tdc);
 	/*
-	 * Check for any running tasklets and kill them
+	 * Check for any running tasklets and kill them.
+	 * But since this function can be invoked from tasklet itself,
+	 * avoid self-destruct which would cause forever loop.
 	 */
 	if (tdc->tasklet_active) {
 		tdc->busy = true;
 		spin_unlock_irqrestore(&tdc->lock, flags);
-		dev_warn(tdc2dev(tdc), "Killing tasklet\n");
-		tasklet_kill(&tdc->tasklet);
+		if (!in_interrupt()) {
+			dev_warn(tdc2dev(tdc), "Killing tasklet\n");
+			tasklet_kill(&tdc->tasklet);
+		}
 		spin_lock_irqsave(&tdc->lock, flags);
 		tdc->busy = false;
 	}