linux-kernel - Re: [PATCH 1/2] staging: iio: adc: ad7192: Add clock for external clock reference

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Date:   Thu, 13 Dec 2018 17:39:22 -0800
From:   Stephen Boyd <sboyd@...nel.org>
To:     Jonathan Cameron <jic23@...nel.org>,
        Mircea Caprioru <mircea.caprioru@...log.com>
Cc:     Michael.Hennerich@...log.com, knaack.h@....de, lars@...afoo.de,
        pmeerw@...erw.net, gregkh@...uxfoundation.org,
        linux-kernel@...r.kernel.org, linux-iio@...r.kernel.org,
        devel@...verdev.osuosl.org, Rob Herring <robh+dt@...nel.org>,
        linux-clk@...r.kernel.org
Subject: Re: [PATCH 1/2] staging: iio: adc: ad7192: Add clock for external clock reference

Quoting Jonathan Cameron (2018-12-08 07:29:54)
> On Thu, 6 Dec 2018 11:10:51 +0200
> Mircea Caprioru <mircea.caprioru@...log.com> wrote:
> 
> > This patch adds a clock to the state structure of ad7192 for getting the
> > external clock frequency. This modifications is in accordance with clock
> > framework dt bindings documentation.
> > 
> > Signed-off-by: Mircea Caprioru <mircea.caprioru@...log.com>
> 
> +cc Rob and the clk list for advise on how to do the binding for this one.
> 
> It is basically 2 pins, you can put a clock in on one of them or connect
> a crystal across them.  The driver has to set a register to say which is
> the case.  
> 
> Current proposal is two optional clocks (fall back to internal oscillator)
> but that doesn't seem to be commonly done, so I'm wondering if there
> is a 'standard' way to handle this sort of thing.
> 

I'm not sure I fully understand, but I think perhaps
assigned-clock-parents would work? Or does that not work because either
way some parent is assigned, either the crystal or the optional clk that
isn't a crystal?