Re: [PATCH] Fix suspend/resume of pxa_camera driver

Guennadi Liakhovetski
2008-07-27T19:11:43Z

On Sun, 27 Jul 2008, Robert Jarzmik wrote:

> Yes, I have tested, with a complete suspend/resume cycle on a Mitac Mio A701
> smartphone. And yes, the PXA suspend is based on SDRAM being in self refresh
> state. I'm speaking of suspend, not standby, there's no confusion here.
>
> Notice I always go into suspend while _not_ in active capturing. That could
> change things.

Yes, this is the difference. The sensor is attached to the camera host
only on open. In fact, I am not sure, how video applications should behave
during a suspend / resume cycle. If you suspend, while, say, recording
from your camera, should you directly continue recording after a wake up?
How do currect drivers implement this? Or, in general, for example with
audio - if you suspend while listening to a stream over the net, or to a
CD, or to a mp3-file on your local disk, should the sound resume after a
wake up? I added linux-pm for some authoritative answers:-)

If you know how a v4l2 device should handle suspend/resume, or when we get
some answers, let's try to do it completely-

> Have you previously tested the pxa_camera driver in suspend ?

No, I have not. I didn't have power-management enabled on my board, and I
don't know how easy such tests would be on my hardware. That's why I just
removed all suspend/resume code from the pxa270 driver completely.

> For history, my setup is :
> - a pxa272 on a Mio A701 board
> - a Micron MT9M111 chip (driver under construction)
>
> For the camera part, by now, I'm using standard suspend/resume functions of the
> platform driver (mt9m111.c). It does work, but it's not clean ATM. The chaining
> between the driver resume function and the availability of the I2C bus are not
> properly chained. I'm still working on it.

Yes, we have to clarify this too.

Thanks
Guennadi
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Guennadi Liakhovetski, Ph.D.
Freelance Open-Source Software Developer