linux-kernel - Re: [PATCH v4 2/2] spi: add driver for J-Core SPI controller

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Date:	Thu, 28 Jul 2016 20:51:25 +0100
From:	Mark Brown <broonie@...nel.org>
To:	Rich Felker <dalias@...c.org>
Cc:	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-spi@...r.kernel.org, linux-sh@...r.kernel.org,
	Rob Herring <robh+dt@...nel.org>,
	Mark Rutland <mark.rutland@....com>
Subject: Re: [PATCH v4 2/2] spi: add driver for J-Core SPI controller

On Thu, Jul 28, 2016 at 03:40:45PM -0400, Rich Felker wrote:
> On Thu, Jul 28, 2016 at 08:11:53PM +0100, Mark Brown wrote:

> > An architecture or SoC dependency with || COMPILE_TEST would be useful
> > for avoiding cluttering Kconfig for other users.  Though as this is in a
> > FPGA it's perhaps likely people will pick this up for other FPGAs so
> > perhaps a comment to that effect if it seems likely.

> Unlike some of the other SoC hardware (interrupt controller) that's
> more closely tied to the SH cpu trap behavior, the SPI master seems
> like something that would be nice and easy to reuse elsewhere. I don't
> feel strongly about it either way though; I can add the arch dep if
> you want.

I guess it depends if anyone is actually doing that or not, if nobody is
the dependency would be better.

> > Why are you not using the clock API for this?  Just require a clock and
> > use clk_get_rate() to find out what rate it is.

> I thought about that but I'm not familiar with it. I can try to figure
> it out quickly and test that approach; don't see any reason it
> shouldn't work. Would you insist on having full support for
> enabling/disabling the clk when it's in use, or would you be happy
> with treating it as a fixed clock that's always-on for now and
> possibly extending it with more functionality later if there's ever
> hardware where that's relevant/helpful?

It's fine to just enable it at startup and leave it on, though the
runtime PM ops are trivial and you can set auto_runtime_pm to have the
core do the gets and puts.

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