Re: [PATCH RFC 1/1] ASoC: fsl_ssi: Make fifo watermark and maxburst settings device tree options

From: Nicolin Chen
Date: Fri Jan 15 2016 - 13:38:38 EST

On Fri, Jan 15, 2016 at 09:03:28AM -0800, Caleb Crome wrote:

> If nobody objects, we can just set the value to 4 and be done with it.

I agree. And we may apply it only to i.MX platforms with DMA if
other platform owners feel comfortable with the previous settings.

> Another question: is the watermark ever going to be different than
> maxburst? Is there any reason to have them different?

The watermark is merely a threshold to trigger a DMA request. The
only relationship with the burst size is that each burst transfer
should not carry more data than the number of empty slots; FIFO
under/overflow occurs otherwise. So it's just more efficient and
safer to set an identical value to both of them. I don't think
it will cause functional problems to set TFWM to 4 and burst size
to 1 -- It just lets DMA operate in a single data transfer mode.