andy git 06/15 suspend/resume observations

[Graeme Gregory]

On Mon, Jun 16, 2008 at 09:20:15AM +0100, Andy Green wrote:
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> Somebody in the thread at some point said:
> | On Sun, Jun 15, 2008 at 08:08:52PM -0700, Sean McNeil wrote:
> |> Cons:
> |> audio pop is still there for me. I don't know if you committed changes
> |> that should affect it. When I do fully resume and write to the device
> it
> |> hangs. Perhaps they are both related to something with DMA? I get
> around
> |>
> | I suspect this is
> |
> | http://docs.openmoko.org/trac/ticket/1353
> |
> | Rearing its ugly head.
>
> Thanks for the hint!
>
> | Someone please tell me why I cant read that register successfully during
> | resume???????
> |
> | Its as though the kernel caches it.
>
> The only way it could "cache" it is if the iis memory mapped register
> region of cpu space was literally marked as cacheable, because readl()
> is just reading memory.  So I think you can read from it OK.
>
> It doesn't necessarily follow that LRCK is actually toggling at that
> time because nulling the test out get you working; something might be
> done later that gets LRCK going subsequently.
>
> For example I notice we disable IIS clock in suspend, this is re-enabled
> by the time we start looking?  What if s3c24xx_i2s_trigger() ->
> s3c24xx_snd_lrsync() happens before resume of IIS that re-enables the
> unit clock?
>
Resume has finished by this point, we are in Unfreezing apps and
user space code is running.

I set the timeout to be insanely long of 5 minutes and still never got
a l/r clock. But if you start a new stream within this same period
l/r clock works fine.

Graeme