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

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Date:	Thu, 13 Aug 2015 16:34:13 +0800
From:	Hanjun Guo <hanjun.guo@...aro.org>
To:	David Daney <ddaney@...iumnetworks.com>,
	Catalin Marinas <catalin.marinas@....com>
CC:	mark.rutland@....com, linux-mips@...ux-mips.org,
	david.daney@...ium.com, netdev@...r.kernel.org, rafael@...nel.org,
	linux-kernel@...r.kernel.org, tomasz.nowicki@...aro.org,
	rrichter@...ium.com, linux-acpi@...r.kernel.org,
	ddaney.cavm@...il.com, sgoutham@...ium.com,
	David Miller <davem@...emloft.net>,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2 0/2] net: thunder: Add ACPI support.

On 08/12/2015 11:36 PM, David Daney wrote:
> 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@...il.com>
>>>> 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.

Yes. on the other hand, if no DT is provided, will try ACPI even
if no acpi=force on the kernel cmd line.

>>
>> 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().

I'm very keen on seeing that happens :)

Thanks
Hanjun
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