[PATCH v2] ARM: pl330: Fix a race condition

[Boojin Kim]

Javi Merino wrote:

> > On Samsung's Exynos4 platform, while testing audio playback with i2s
> > interface, the above change causes the playback to freeze. The
> > _thrd_active(thrd) call always returns '1' and hence _start(thrd) is
> > not getting called.
>
> If _thrd_active(thrd) returns '1', that means there is an active
> transfer still running or, if it has finished, you haven't called
> pl330_update() to acknowledge that.  pl330_update() calls _start() as
> soon as it can.
>
> drivers/dma/pl330.c registers the irq handler in pl330_probe(), so
> when
> the transaction finishes, pl330_update() should clear it and call
> _start().  If there is any outstanding transaction, it should start
> straight away. If there isn't, it would mark the channel as free, so
> _thrd_active() should return '0'.  If _thrd_active() is still '1', then
> something has gone wrong in the way.
>
> Does this shed some light?
>

Your patch makes the memcpy operation on dmatest.c and net DMA be frozen too
as well as Samsung audio playback.
With our patch, common DMA memcpy sequence may be changed.
I think..
it's needed to find the other way not to bring these side effects.

> Cheers,
> Javi
>
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