Re: [PATCH v2 0/2] net: thunder: Add ACPI support.

[David Daney]

On 08/12/2015 08:23 AM, Catalin Marinas wrote:
> On Tue, Aug 11, 2015 at 01:04:55PM -0700, David Daney wrote:
> > On 08/11/2015 11:49 AM, David Miller wrote:
> > > From: David Daney <ddaney.cavm@xxxxxxxxx>
> > > Date: Mon, 10 Aug 2015 17:58:35 -0700
> > >
> > > > Change from v1:  Drop PHY binding part, use fwnode_property* APIs.
> > > >
> > > > The first patch (1/2) rearranges the existing code a little with no
> > > > functional change to get ready for the second.  The second (2/2) does
> > > > the actual work of adding support to extract the needed information
> > > >from the ACPI tables.
> > >
> > > Series applied.
> >
> > Thank you very much.
> >
> > > In the future it might be better structured to try and get the OF
> > > node, and if that fails then try and use the ACPI method to obtain
> > > these values.
> >
> > Our current approach, as you can see in the patch, is the opposite.  If ACPI
> > is being used, prefer that over the OF device tree.
> >
> > You seem to be recommending precedence for OF.  It should be consistent
> > across all drivers/sub-systems, so do you really think that OF before ACPI
> > is the way to go?
>
> On arm64 (unless you use a vendor kernel), DT takes precedence over ACPI
> if both arm provided to the kernel (and it's a fair assumption given
> that ACPI on ARM is still in the early days). You could also force ACPI
> with acpi=force on the kernel cmd line and the arch code will not
> unflatten the DT even if it is provided, therefore is_of_node(fwnode)
> returning false.
>
> I haven't looked at your driver in detail but something like AMD's
> xgbe_probe() uses a single function for both DT and ACPI with
> device_property_read_*() functions getting the information from the
> correct place in either case. The ACPI vs DT precedence is handled by
> the arch boot code, we never mix the two and confuse the drivers.

My long term plan is to create something like 
firmware_get_mac_address(), that would encapsulate  of_get_mac_address() 
and the ACPI equivalent.

Same for firmware_phy_find_device().

These would function as you suggest, but lacking this infrastructure, we 
implemented this patch set instead.

Thanks,
David Daney
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