linux-kernel - Re: [PATCH] Documentation: dt: bindings: TI WiLink modules

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Date:	Thu, 27 Jun 2013 07:51:32 -0500
From:	Nishanth Menon <nm@...com>
To:	Luciano Coelho <coelho@...com>
CC:	Nishanth Menon <menon.nishanth@...il.com>,
	<grant.likely@...aro.org>, <rob.herring@...xeda.com>,
	<devicetree-discuss@...ts.ozlabs.org>, <linux-doc@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <linux-wireless@...r.kernel.org>,
	<tony@...mide.com>, <linux-omap@...r.kernel.org>,
	<linux-arm@...r.kernel.org>
Subject: Re: [PATCH] Documentation: dt: bindings: TI WiLink modules

On 11:47-20130627, Luciano Coelho wrote:
> (added mailing lists and everyone back to the thread)
> 
> On Wed, 2013-06-26 at 23:38 -0500, Nishanth Menon wrote:
> > On 06/25/2013 03:35 AM, Luciano Coelho wrote:
> > > +Optional properties:
> > > +--------------------
> > > +
> > > +- refclock: the internal WLAN reference clock frequency (required for
> > > +  WiLink6 and WiLink7; not used for WiLink8).  Must be one of the
> > > +  following:
> > > +	0 = 19.2 MHz
> > > +	1 = 26.0 MHz
> > > +	2 = 38.4 MHz
> > > +	3 = 52.0 MHz
> > > +	4 = 38.4 MHz, XTAL
> > > +	5 = 26.0 MHz, XTAL
> > > +
> > > +- tcxoclock: the internal WLAN TCXO clock frequency (required for
> > > +  WiLink7 not used for WiLink6 and WiLink8).  Must be one of the
> > > +  following:
> > > +	0 = 19.200 MHz
> > > +	1 = 26.000 MHz
> > > +	2 = 38.400 MHz
> > > +	3 = 52.000 MHz
> > > +	4 = 16.368 MHz
> > > +	5 = 32.736 MHz
> > > +	6 = 16.800 MHz
> > > +	7 = 33.600 MHz
> > >
> > just a gentle query - why not use frequency itself here in Hz for 
> > refclock and txoclk?
> 
> I thought about using the actual frequencies, but I decided not to do
> so, because I'd have to convert them to these values anyway.  These
> values are used to configure the firmware and it uses these
> "enumerations".
Could we not hide this under preprocessor macros instead? just wondering
of txoclock = <6>; kind of usage.. easy to make mistakes and easier to
confuse a new reader :).

just my 2 cents.
> 
> 
> > might not another option of using
> > node {
> > clocks=<&clk>;
> > }
> > 
> > Usually refclock is an external clock source, no?
> 
> No.  In the WiLink case, both refclock and tcxoclock are internal
> clocks.  They are in the module itself and what we need to do is tell
> the WiLink chip what the module's clocks look like.
> 
> 
> > the above allows you to do an devm_clk_get and clk_get_rate() to figure 
> > out the exact clock frequency.
> 
> No, we can't use these calls, because they are internal clocks.
> 
> Please see my more complete explanation as an answer to Tony's email.
K thanks.
> 
> Thanks for your review!

Glad to be of help.

-- 
Regards,
Nishanth Menon
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