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Message-ID: <4E42C196.7030708@freescale.com>
Date: Wed, 10 Aug 2011 12:36:22 -0500
From: Scott Wood <scottwood@...escale.com>
To: Robin Holt <holt@....com>
CC: Kumar Gala <galak@...nel.crashing.org>,
Wolfgang Grandegger <wg@...ndegger.com>,
U Bhaskar-B22300 <B22300@...escale.com>,
Grant Likely <grant.likely@...retlab.ca>,
Marc Kleine-Budde <mkl@...gutronix.de>,
<socketcan-core@...ts.berlios.de>, <netdev@...r.kernel.org>,
PPC list <linuxppc-dev@...ts.ozlabs.org>,
<devicetree-discuss@...ts.ozlabs.org>
Subject: Re: [PATCH v11 5/5] powerpc: Fix up fsl-flexcan device tree binding.
On 08/10/2011 12:19 PM, Robin Holt wrote:
> On Wed, Aug 10, 2011 at 11:56:28AM -0500, Scott Wood wrote:
>> On 08/10/2011 11:27 AM, Robin Holt wrote:
>>> -CPI Clock- Can Protocol Interface Clock
>>> - This CLK_SRC bit of CTRL(control register) selects the clock source to
>>> - the CAN Protocol Interface(CPI) to be either the peripheral clock
>>> - (driven by the PLL) or the crystal oscillator clock. The selected clock
>>> - is the one fed to the prescaler to generate the Serial Clock (Sclock).
>>> - The PRESDIV field of CTRL(control register) controls a prescaler that
>>> - generates the Serial Clock (Sclock), whose period defines the
>>> - time quantum used to compose the CAN waveform.
>>> +- compatible : Should be "fsl,flexcan" and optionally
>>> + "fsl,flexcan-<processor>"
>>
>> fsl,<processor>-flexcan, and it should not be optional, and should come
>> before "fsl,flexcan".
>>
>> Also may want to list fsl,p1010-rdb as a "canonical compatible" for
>> anything which is backwards compatible with p1010's implementation.
>
> How do I specify 'canonical compatible'?
Something like:
compatible: Should be "fsl,<processor>-flexcan" and "fsl,flexcan".
An implementation should also claim any of the following compatibles
that it is fully backwards compatible with:
- fsl,p1010-rdb
> What would be the use of it in that implementation?
It limits the number of compatibles a driver has to care about, so you
don't need a huge ID table just to be able to figure out whether this is
a p1010-style flexcan or ARM-style.
-Scott
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