Re: propper support of 5 wire SPI (SPI_READY signal)

[Mark Brown <broonie-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>]

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On Fri, Feb 19, 2016 at 10:08:46AM +0100, Oleksij Rempel wrote:

> i'm working on a project which depends on 5 Wire SPI communication. It
> is probably identical to spi-davinci.c with SPI_READY signal. Only
> difference is that SPI_READY is not supported by hardware, in this case
> GPIO input is used.

> Currently this project implements SPI_READY and CS on top of spidev
> driver. What makes it really ugly, slow and complicated.

> My question is, are there any better, upstreamable way to implement it?
> For example directly insight of spi framework? Any suggestions and
> comments are welcome.

Unless the hardware support SPI_READY a GPIO is going to be as good as
it gets I think, someone else might have better ideas but nothing
springs to mind for me.  I'd be OK with a GPIO based implementation in
the core for systems that don't have hardware support for it but I don't
see anything that'd be fundamentally better in terms of system
performance right now.

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