Messages in this thread | | | Date | Thu, 25 Apr 2013 15:21:06 +0200 | Subject | Re: [PATCH 04/32] dmaengine: ste_dma40: Amalgamate DMA source and destination channel numbers | From | Linus Walleij <> |
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On Thu, Apr 25, 2013 at 3:09 PM, Russell King - ARM Linux <linux@arm.linux.org.uk> wrote:
> There's a problem with device to device transfers though - you have to > consider the rate at which the devices produce and consume data, and > whether they both can cope with differing data rates. > > Take for instance your audio in to audio out idea - even if they are > both operating at the same bits per sample and sample rate, if they are > independently clocked, chances are that the clocks are not exactly the > same, which means you will either underrun or overrun one of the FIFOs > in the system.
This magically works for us, but yes, I think they had to use the same clock (simplest solution, anyway).
It is/was a very real usecase, IIRC coming from roundtrip constraints in the GSM 3GPP spec, wanting to keep the latency as low as possible. With this scheme there is no more than a FIFO on each end of delay, which is nice.
Yours, Linus Walleij
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