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Subject: Re: [PATCH] i2c-qoriq: modified compatibility for correct prescaler
From: Scott Wood <scottwood@freescale.com>
To: Wolfram Sang <wsa@the-dreams.de>
Date: Fri, 26 Dec 2014 20:43:40 -0600
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Cc: Valentin Longchamp <valentin.longchamp@keymile.com>,
 Linux device trees <devicetree@vger.kernel.org>, danielle.costantino@gmail.com,
 "Boschung, Rainer" <Rainer.Boschung@keymile.com>, "Brunck,
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On Tue, 2014-12-23 at 14:49 +0100, Wolfram Sang wrote:
> On Tue, Dec 23, 2014 at 02:23:01PM +0100, Valentin Longchamp wrote:
> > Wolfgang, Scott,
> 
> Wolfram, please.
> 
> > > What is then the agreement here ? Add a clock-div to the device trees ? Or do
> > > something similar to  mpc_i2c_get_sec_cfg_8xxx() ?
> > > 
> > > I think the clock-div property is better according to Freescale's AN 2919
> > > section 3.1 Source clock. All the source clocks are fixed (with a clock-div of 2
> > > in case of mpc8536/43/45/47/48/67/68/72, plus p2020) except for the mpc8533/44
> > > where it can be 2 or 3, and that's what mpc_i2c_get_sec_cfg_8xxx() determines.
> > > 
> > > So mpc_i2c_get_sec_cfg_8xxx() should remain the exception and the other
> > > prescaler values should be derived from an additional clock-div that must be
> > > added in the respective device trees (at least for the qoriq devices, because
> > > for instance mpc8543 already has the correct prescaler thanks to
> > > mpc_i2c_data_8543 from i2c-mpc.c).
> > > 
> > 
> > Do you have an opinion on the above ?
> 
> I don't mind. I'll leave it to PowerPC experts to judge if a new binding
> is apropriate or reading SVR is the way to go. If it is going to be a
> new binding, then please look around before if there is already
> something similar around...

I'd rather use SVR so things work with existing device trees.

-Scott