On Mon, Aug 24, 2015 at 02:22:49PM +0100, Jon Hunter wrote:

On 24/08/15 10:22, Vinod Koul wrote:

quoted

On Mon, Aug 24, 2015 at 09:47:13AM +0100, Jon Hunter wrote:

quoted

On 23/08/15 15:17, Vinod Koul wrote:

quoted

On Tue, Aug 18, 2015 at 02:49:09PM +0100, Jon Hunter wrote:

quoted

@@ -1543,7 +1531,7 @@ static int tegra_dma_pm_suspend(struct device *dev)
 	int ret;
 
 	/* Enable clock before accessing register */
-	ret = tegra_dma_runtime_resume(dev);
+	ret = pm_runtime_get_sync(dev);

why is this required ?

Because the clock could be disabled when this function is called. This
function saves the DMA context so that if the context is lost during
suspend, it can be restored.

Have you verified this? Coz my understanding is that when PM does suspend it
will esnure you are runtime resume if runtime suspended and then will do
suspend.
So you do not need to do above

I see what you are saying. I did some testing with ftrace today to trace
rpm and suspend/resume calls. If the dma controller is runtime suspended
and I do not call pm_runtime_get_sync() above then I do not see any
runtime resume of the dma controller prior to suspend. Now I was hoping
that this would cause a complete kernel crash but it did not and so the
DMA clock did not appear to be needed here (at least on the one board I
tested). However, I would not go as far as to remove this and prefer to
keep as above.

Okay am adding Rafael here for his recommendations.

I have tested in past and if my driver was runtime suspended we were resumed
prior to being suspended. So I am not sure why you did not see that
behaviour, and if that is right we don't need to force resume here

-- 
~Vinod