Messages in this thread | | | Subject | Re: [RFC PATCH 1/7] DMA: tegra-apb: Correct runtime-pm usage | From | Jon Hunter <> | Date | Fri, 28 Aug 2015 11:30:50 +0100 |
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On 25/08/15 23:46, Rafael J. Wysocki wrote: > On 8/25/2015 11:37 AM, Jon Hunter wrote:
[snip]
>> Vinod, thinking about this some more, I am wondering if it is just >> better to get rid of the suspend/resume callbacks and simply handling >> the state in the runtime suspend/resume callbacks. I think that would be >> safe too, because once the clock has been disabled, then who knows what >> the context state will be. > > One caveat here: system suspend may be invoked at any time, so you need > to ensure that the device is properly suspended when that happens. > > I believe you at least need a ->suspend callback for that.
Thanks, makes sense.
On a related note, I see a few drivers, including this DMA driver doing the following in the driver ->remove callback.
pm_runtime_disable(&pdev->dev); !pm_runtime_status_suspended(&pdev->dev)) tegra_dma_runtime_suspend(&pdev->dev);
I understand that the code is trying to ensure that the device is suspended regardless of whether rpm is enabled or not in the kernel config. However, looking at the pm_runtime_status_suspended() function, AFAICT, it will always return false above as the disable_depth will be greater than 0. So I am concerned that the tegra_dma_runtime_suspend() is called even when not needed? However, I could also be missing something here.
Cheers Jon
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