[PATCH v4] ARM: omap: edma: add suspend suspend/resume hooks

[Vaibhav Bedia]

Hi Daniel,

On Wed, Oct 30, 2013 at 4:21 PM, Daniel Mack <zonque at gmail.com> wrote:
[...]
> +
> +static SIMPLE_DEV_PM_OPS(edma_pm_ops, edma_pm_suspend, edma_pm_resume);
> +
>  static struct platform_driver edma_driver = {
>         .driver = {
>                 .name   = "edma",
> +               .pm     = &edma_pm_ops,
>                 .of_match_table = edma_of_ids,
>         },

A while back we discovered a nasty race condition here that had us move the EDMA
PM callbacks to the noirq phase. IIRC the MMC driver was resuming
before the EDMA
driver had a chance to run and that was leading to a deadlock. I am
not sure how to force
this scenario but i do remember spending time debugging this on a
random codebase.
Maybe some else has some better ideas on how to force this race condition...

I think logically it makes sense to have the DMA controllers in any
system resume before
any of the client drivers. Maybe a set of syscore_ops similar to the
timekeeping stuff needs
to be added (in the dmaengine framework?) to get this right.

Regards,
Vaibhav