[PATCH 2/2] DMA: PL08x: fix channel pausing to timeout rather than lockup

[Dan Williams]

On Thu, Jan 27, 2011 at 4:37 AM, Russell King - ARM Linux
<linux at arm.linux.org.uk> wrote:
> If a transfer is initiated from memory to a peripheral, then data is
> fetched and the channel is marked busy.  This busy status persists until
> the HALT bit is set and the queued data has been transfered to the
> peripheral.  Waiting indefinitely after setting the HALT bit results in
> system lockups.  Timeout this operation, and print an error when this
> happens.
>
> Signed-off-by: Russell King <rmk+kernel at arm.linux.org.uk>
> ---
> This happens when a M->P transfer is started, but the peripheral doesn't
> take the data.  The DMA controller will mark itself active and fetch data
> from memory, in anticipation of the peripheral wanting the data.  This
> advances the source address.
>
> An alternative approach here is to just set the HALT bit and return
> immediately, without waiting for the primecell to show that it is no
> longer active.  In any case, resuming the channel will allow the
> transfer to continue without data loss.
>

Ok, and the other infinite busy wait in pl08x_start_txd() is
guaranteed to be after a resume operation, or does it also need a
timeout?

--
Dan