Re: Tearing down DMA transfer setup after DMA client has finished

From: Mason
Date: Thu Dec 08 2016 - 07:17:59 EST

On 08/12/2016 13:03, Geert Uytterhoeven wrote:

> MÃns RullgÃrd wrote:
>> Geert Uytterhoeven writes:
>>> Can you fall back to PIO if requesting a channel fails?
>> Why are we debating this nonsense? There is an easy fix that doesn't
>> require changing the semantics of existing functions or falling back to
>> slow pio.
> You still want to fall back to PIO if the DMA engine is not available
> at all (e.g. DMA engine driver not compiled in, or module not loaded).

FWIW, the ECC engine is tied to the DMA engine. So PIO means
not only taking a hit from tying up the CPU for a slooow
transfer, but also a huge hit if ECC must be computed in SW.
(A 100x perf degradation is not unlikely.)