From: nm@ti•com (Nishanth Menon)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH v5] ARM: omap: edma: add suspend suspend/resume hooks
Date: Fri, 8 Nov 2013 12:03:16 -0600 [thread overview]
Message-ID: <527D2764.5060308@ti.com> (raw)
In-Reply-To: <527D0DE6.6090506@ti.com>
On 11/08/2013 10:14 AM, Joel Fernandes wrote:
> On 11/08/2013 12:28 AM, Kevin Hilman wrote:
> [..]
>>>> Also, I believe it was already suggested by Nishanth, but the late/early
>>>> callbacks are probably more appropriate here than the noirq callbacks.
>>>> Unless there's a *really* good reason to use the noirq callbacks, they
>>>> should be avoided.
>>>>
>>>> That being said, I wonder if the whole approach here is the right one.
>>>> I know you're basing your stuff on some TI tree, but that doesn't make
>>>> it the right way (usually, it's the opposite, but I digress...) ;)
>>>>
>>>> IMO, EDMA should be done like we currently do I2C and not implement
>>>> suspend/resume at all. Instead, the driver should do runtime PM done on
>>>
>>> But a potential problem with this is powering edma on or off between xfers may
>>> slow things down quite a bit because xfers happen so much often and there is
>>> some overhead in the pm_runtime calls which adds up overtime when dealing with
>>> something as frequent as EDMA. Also we would lose the global EDMA context right
>>> so we'd have to restore the context every time during runtime PM (?).
>>
>> Have a look at the autosuspend feature of runtime PM. (c.f.
>> Documentation/power/pm_runtime.txt)
>
> Sure, will do that. Thanks :)
>
> Just one more silly question, in very frequent operations is there no over-head
> even when using autosuspend? Because when I traced last time (without
> autosuspend), the depth of pm runtime calls were quite a lot but this could also
> be because of the OMAP implementation.
that is the entire purpose of autosuspend - the back2back calls have
almost no overhead (other than to see that device suspend was not
invoked) - this is pretty fast. you can tweak autosuspend timeout for
the right configuration to meet up with what you need.
--
Regards,
Nishanth Menon
next prev parent reply other threads:[~2013-11-08 18:03 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-11-07 22:32 [PATCH v5] ARM: omap: edma: add suspend suspend/resume hooks Daniel Mack
2013-11-08 0:02 ` Kevin Hilman
2013-11-08 4:58 ` Joel Fernandes
2013-11-08 6:28 ` Kevin Hilman
2013-11-08 16:14 ` Joel Fernandes
2013-11-08 18:03 ` Nishanth Menon [this message]
2013-11-08 18:51 ` Kevin Hilman
2013-11-08 7:59 ` Daniel Mack
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