linux-kernel - Re: [PATCH v1 1/5] ARM: imx28: add basic dt support

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Date:	Wed, 14 Mar 2012 20:45:23 +0800
From:	Dong Aisheng <aisheng.dong@...escale.com>
To:	Grant Likely <grant.likely@...retlab.ca>
CC:	Dong Aisheng-B29396 <B29396@...escale.com>,
	"devicetree-discuss@...ts.ozlabs.org" 
	<devicetree-discuss@...ts.ozlabs.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
	Guo Shawn-R65073 <r65073@...escale.com>,
	"kernel@...gutronix.de" <kernel@...gutronix.de>,
	"rob.herring@...xeda.com" <rob.herring@...xeda.com>,
	"cjb@...top.org" <cjb@...top.org>,
	"rdunlap@...otime.net" <rdunlap@...otime.net>,
	"vinod.koul@...ux.intel.com" <vinod.koul@...ux.intel.com>
Subject: Re: [PATCH v1 1/5] ARM: imx28: add basic dt support

On Wed, Mar 14, 2012 at 01:23:51AM +0800, Grant Likely wrote:
> On Tue, 13 Mar 2012 16:47:04 +0800, Dong Aisheng <b29396@...escale.com> wrote:
> > From: Dong Aisheng <dong.aisheng@...aro.org>
> > 
> > This patch includes basic dt support which can boot via nfs rootfs.
> > 
> > Signed-off-by: Dong Aisheng <dong.aisheng@...aro.org>
> > ---
> >  Documentation/devicetree/bindings/arm/fsl.txt |    4 +
> >  arch/arm/boot/dts/imx28-evk.dts               |   31 +++++++++
> >  arch/arm/boot/dts/imx28.dtsi                  |   88 +++++++++++++++++++++++++
> >  arch/arm/mach-mxs/Kconfig                     |    9 +++
> >  arch/arm/mach-mxs/Makefile                    |    1 +
> >  arch/arm/mach-mxs/imx28-dt.c                  |   67 +++++++++++++++++++
> >  6 files changed, 200 insertions(+), 0 deletions(-)
> > 
> > diff --git a/Documentation/devicetree/bindings/arm/fsl.txt b/Documentation/devicetree/bindings/arm/fsl.txt
> > index 54bddda..9f21faf 100644
> > --- a/Documentation/devicetree/bindings/arm/fsl.txt
> > +++ b/Documentation/devicetree/bindings/arm/fsl.txt
> > @@ -1,6 +1,10 @@
> >  Freescale i.MX Platforms Device Tree Bindings
> >  -----------------------------------------------
> >  
> > +i.MX28 Evaluation Kit
> > +Required root node properties:
> > +    - compatible = "fsl,imx28-evk", "fsl,imx28";
> > +
> >  i.MX51 Babbage Board
> >  Required root node properties:
> >      - compatible = "fsl,imx51-babbage", "fsl,imx51";
> > diff --git a/arch/arm/boot/dts/imx28-evk.dts b/arch/arm/boot/dts/imx28-evk.dts
> > new file mode 100644
> > index 0000000..9758dc4
> > --- /dev/null
> > +++ b/arch/arm/boot/dts/imx28-evk.dts
> > @@ -0,0 +1,31 @@
> > +/*
> > + * Copyright 2012 Freescale Semiconductor, Inc.
> > + *
> > + * The code contained herein is licensed under the GNU General Public
> > + * License. You may obtain a copy of the GNU General Public License
> > + * Version 2 or later at the following locations:
> > + *
> > + * http://www.opensource.org/licenses/gpl-license.html
> > + * http://www.gnu.org/copyleft/gpl.html
> > + */
> > +
> > +/dts-v1/;
> > +/include/ "imx28.dtsi"
> > +
> > +/ {
> > +	model = "Freescale i.MX28 Evaluation Kit";
> > +	compatible = "fsl,imx28-evk", "fsl,imx28";
> > +
> > +	memory {
> > +		device_type = "memory";
> > +		reg = <0x40000000 0x08000000>;
> > +	};
> > +
> > +	ahb@...80000 {
> > +		fec@...f0000 {
> > +			phy-mode = "rmii";
> > +			local-mac-address = [00 04 9F 01 7D 5B];
> 
> Generally a bad idea to put a specific mac address into the device tree.
> Better to fill it with zeros.  Otherwise all the dev boards will end up using
> the same value.
> 
Yes, this issue also exists on other platfroms like mx6q.
One way is to dynamically get mac address by reading otp register as non-dt does
like:
static int __init mx28evk_fec_get_mac(void)
{
        int i;
        u32 val;
        const u32 *ocotp = mxs_get_ocotp();

        if (!ocotp)
                return -ETIMEDOUT;

        /*
         * OCOTP only stores the last 4 octets for each mac address,
         * so hard-code Freescale OUI (00:04:9f) here.
         */
        for (i = 0; i < 2; i++) {
                val = ocotp[i];
                mx28_fec_pdata[i].mac[0] = 0x00;
                mx28_fec_pdata[i].mac[1] = 0x04;
                mx28_fec_pdata[i].mac[2] = 0x9f;
                mx28_fec_pdata[i].mac[3] = (val >> 16) & 0xff;
                mx28_fec_pdata[i].mac[4] = (val >> 8) & 0xff;
                mx28_fec_pdata[i].mac[5] = (val >> 0) & 0xff;
        }

        return 0;
}

But it seems this needs pass mac address to fec driver via platforom data which is
not friendly to dt.

Another way may be changing fec driver to get the fixed part of mac address(first
two bytes) from device tree and read the left dynamical part from otp which i'm not
sure is better enough.

BTW, filling with zeros seems not work since it's invalid mac address.

Regards
Dong Aisheng



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