On Tue, 1 Jun 2010 11:19:30 +0300 Peter Ujfalusi <peter.ujfalusi@xxxxxxxxx> wrote: > If threshold is configured to 100 (99 in register), than McBSP will asserts the > DMA request line, when 100 locations are free. Than DMA has to send 100 words > per DMA request. > > So we need to limit the period size (which is used to configure the DMA's elem > count - number of words per DMA request) that it shall never be bigger than the > threshold. > Now I get it with some get hands dirty testing :-) So this is a feature of SDMA that in threshold mode the transfer size must equal or smaller than threshold (as says the TRM). Still don't understand why the transfer size is dependent on peripheral FIFO threshold size but that's the fact and we must obey it as Eduardo's original patch and your's are doing. > If there is interest, I might look at this. > I guess this could be useful on McBSP1,3,4, and 5, which has small FIFO... > Yes, have a packet based DMA transfer saving power and then we have bunch of interrupts coming :-) -- Jarkko -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
