linux-kernel - Re: [PATCH RFC] clk: Introduce userspace clock driver

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Date:	Mon, 13 May 2013 09:21:35 +0400
From:	Mark Brown <broonie@...nel.org>
To:	Sören Brinkmann <soren.brinkmann@...inx.com>
Cc:	Mike Turquette <mturquette@...aro.org>,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH RFC] clk: Introduce userspace clock driver

On Sun, May 12, 2013 at 12:05:04PM -0700, Sören Brinkmann wrote:
> On Sun, May 12, 2013 at 06:33:44PM +0400, Mark Brown wrote:

> > No, there's no confusion here - the clocks that are being exposed to
> > userspace are the clocks which enter the FPGA.  The driver or whatever
> > that understands the FPGA can do what is needed to control them,
> > including routing them on to subdevices it instantiates or exposing them
> > to userspace.

> Such a driver does not exist in general.
> For some IP cores, Linux drivers do exist and then
> they are supposed to directly use the CCF, IMHO, no need to expose
> things to userspace in that case.
> I'm trying to cover cases, in which there is no driver available/needed for
> the FPGA design, other than some simple clock controls.

You're not understanding the point here.  If you've got a
reprogrammmable FPGA you at least need some way to get the FPGA image in
there.  This driver is presumably responsible for instantiating whatever
is needed to control what is on the FPGA, that could include punting the
clocks to userspace if that's sane.

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