[PATCH v2] OMAP: PM: DMA: Enable runtime pm

[manjugk@ti.com (G, Manjunath Kondaiah)]

Hi Kevin,

On Mon, Feb 14, 2011 at 02:06:53PM -0800, Kevin Hilman wrote:
> "G, Manjunath Kondaiah" <manjugk@ti.com> writes:
> 
> > From: Manjunath G Kondaiah <manjugk@ti.com>
> >
> > Enable runtime pm and use pm_runtime_get_sync and pm_runtime_put_autosuspend
> > for OMAP DMA driver.
> >
> > The DMA driver uses auto suspend feature of runtime pm framework through
> > which the clock gets disabled automatically if there is no activity for
> > more than one second.
> >
> > Testing:
> > Compile: omap1_defconfig and omap2plus_defconfig
> > Boot: OMAP1710(H3), OMAP2420(H4), OMAP3630(Zoom3), OMAP4(Blaze)
> 
> The normal DMA tests should also be run on these platforms.  Based on
> the above, I can't tell any DMA tests were run.   Based on my tests,
> this isn't working for chained xfers.
> 
> Using the runtime PM sysfs interface, you can check the runtime status
> of the device:
> 
> # cat /sys/devices/platform/omap/omap_dma_system.0/power/runtime_status          
> 
> It should show 'active' during transfer, and after timeout expires it
> will show 'suspended'.
> 
> Doing some tests using my dmatest module:
> 
>   git://gitorious.org/omap-test/dmatest.git
> 
> I noticed that it gets stuck in 'active' and never gets suspended when I
> used DMA channel linking (load module using 'linking=1' as load-time option)
> 
> I'm not sure exactly why, but I will guess that the reason is that there
> is an imbalance in get/put calls when using chaining, since 'get' is
> only called once upon omap_start_dma() but 'put' is called for every
> channel in the callback.

Even I noticed this after running chaining test case and checking
runtime status. But, I am wondering even with 'active' runtime status, 
the core hits off and retention.

The complete log which has all the sequences of running chaining tests,
enabling off mode and checking runtime status is available at:
http://pastebin.com/YEHMEXUP

Though I agree on the point that, it is mismatch with get/put calls with
DMA chaining, I still need to analyze this in detail.

The other thing which is not considered here is, the get_sync is called
inside start_dma only(request_dma will call get_sync and put after the
getting requested channel). After request_dma and start_dma, there are
API's called by user(dma_set_params, priority etc) which also require
get_sync since those API's will access configuration registers. I am
wondering if have get_sync and put in all the API's, this might result
in over loading. 

> 
> > On zoom3 core retention is tested with following steps:
> > echo 1 > /debug/pm_debug/sleep_while_idle
> > echo 1 > /debug/pm_debug/enable_off_mode
> > echo 5 > /sys/devices/platform/omap/omap_uart.0/sleep_timeout
> > echo 5 > /sys/devices/platform/omap/omap_uart.1/sleep_timeout
> > echo 5 > /sys/devices/platform/omap/omap_uart.2/sleep_timeout
> > echo 5 > /sys/devices/platform/omap/omap_uart.3/sleep_timeout
> >
> > It is observed that(on pm branch), core retention count gets increasing if the
> > board is left idle for more than 5 seconds. However, it doesnot enter off mode
> > (even without DMA runtime changes).
> 
> What silicon rev is on your Zoom3?  
It's 3630 ES1.0. 
> Mainline kernels now disable core off-mode for 3630 revs < ES2.1 due to erratum 
>i583.
> 
> If this happens, you should see something like this on the console:
> 
>            Core OFF disabled due to errata i583
> 
We can observe above message in mainline after enabling cpu idle in
omap2plus_defconfig.

I switched to zoom2 and able to hit core retention and
off mode with mainline.

-Manjunath