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

[Dong Aisheng <aisheng.dong@freescale.com>]

On Thu, Mar 15, 2012 at 07:22:04PM +0800, Lothar Waßmann wrote:
> Hi,
> 
> Dong Aisheng writes:
> > On Thu, Mar 15, 2012 at 02:53:29PM +0800, Lothar Waßmann wrote:
> > > Hi,
> > > 
> > > Dong Aisheng writes:
> > > > On Wed, Mar 14, 2012 at 10:16:43PM +0800, s.hauer@pengutronix.de wrote:
> > > > > On Wed, Mar 14, 2012 at 08:45:23PM +0800, Dong Aisheng wrote:
> > > > > > On Wed, Mar 14, 2012 at 01:23:51AM +0800, Grant Likely wrote:
> > > [...]
> > > > > > 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.
> > > > > 
> > > > > Yes, that's the idea of using this value...
> > > > > 
> > > > But comparing to use an invalid value, why not just do not define that
> > > > local-mac-address property?
> > > > 
> > > Because a MAC address is by definition a GLOBALLY UNIQUE IDENTIFIER
> > > which is contrary to coding a "valid" default value for it somewhere!
> > > The owner of a certain MAC address range (OUI) is responsible for
> > > ensuring the uniqueness. Thus only they may assign a specific MAC
> > > address to a specific device.
> > > 
> > Yes, you're correct.
> > So i propose to read the MAC address from MX28 OTP in fec driver instead of
> > define it in device tree in my last mail.
> > http://www.spinics.net/lists/arm-kernel/msg165040.html
> > Do you have any comment on that way?
> > 
> That patch sets the OUI to the Freescale owned MAC range. Thus only
> Freescale products may be able to use the driver.
> 
No.
My proposal is only set the fixed part(first two octets) in board dts file,
each board knows it's value, and read the left 4 octets from OCOTP dynamically.
Obviously the freeescale board dts file is only for FSL platforms.
Other platforms can define their fix part of MAC address in their dts file.

> Anyway there is no definite spec how the MAC address(es) are stored
> in the fuse map. Thus reading the MAC from there is more or less
> platform specific.
> 
It's just provide one more option since there are customers storing the MAC
in the fuse map.

> Currently I'm setting up the MAC address for our TX28 from the fuses
> in the platform code passed via platform_data, but that will obviously
> not work with DT.
> 
Non-dt can also use my proposal, then you only need to pass the fixed part of
MAC via platfrom data, the left will be read by fec driver.

> The correct way would probably be to pass the MAC from the bootloader
> via a DT blob. But that would require all bootloaders to be updated
> first to support DTS. :(
> 
But uboot will face the same problem that can not define a valid MAC
in dts, did i undertand correctly?

> An intermediate solution could be using OF_DEV_AUXDATA to pass a
> platform_data struct that may contain a MAC address set up by the
> platform code.
> 
Yes, it's a way but i'm afraid will not get accepted by dt people.

Regards
Dong Aisheng