Re: [PATCH 08/11] MTD: m25p80: Add option to limit SPI transfer size.

Marek Vasut
2015-07-15T17:46:20Z

On Wednesday, July 15, 2015 at 05:59:46 PM, Brian Norris wrote:
> Hi Michal,

Hi all,

> On Wed, Jul 15, 2015 at 01:52:27PM +0200, Marek Vasut wrote:
> > The problem is, if you add a new DT binding, you'd have to support it
> > forever, no matter how bad idea that binding turned out to be.
>
> Agreed, and a solid NAK to this patch. I could have sworn I gave such a
> response when this was originally being discussed a month ago.
>
> AFAICT, you have one of two general approaches available to you:
>
> 1. Fix up the SPI driver so that it knows how to break large SPI
> transfers up into smaller segments that its constituent hardware (DMA
> controllers, fast clocks, etc.) can handle.

I think this might actually be easier -- just do a transfer where you
don't toggle CS and just stops the clock at the last bit, then do another
(multiple) transfers which don't toggle CS at all, then finally do a
transfer which toggles a CS at the end. This should be pretty trivial
to do and I think for example spi-mxs.c does this.

Best regards,
Marek Vasut