linux-kernel - Re: [PATCH v4 2/4] ARM: dts: NSP: Add DT files for Meraki MX64 series

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Date:   Fri, 25 Jun 2021 10:30:33 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Matthew Hagan <mnhagan88@...il.com>, Arnd Bergmann <arnd@...db.de>
Cc:     Florian Fainelli <f.fainelli@...il.com>,
        Vladimir Oltean <olteanv@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Olof Johansson <olof@...om.net>, SoC Team <soc@...nel.org>,
        Ray Jui <rjui@...adcom.com>,
        Scott Branden <sbranden@...adcom.com>,
        bcm-kernel-feedback-list <bcm-kernel-feedback-list@...adcom.com>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Sam Ravnborg <sam@...nborg.org>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        DTML <devicetree@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v4 2/4] ARM: dts: NSP: Add DT files for Meraki MX64 series

On 6/25/21 10:26 AM, Matthew Hagan wrote:
> On 25/06/2021 10:59, Arnd Bergmann wrote:
> 
>> On Fri, Jun 25, 2021 at 11:52 AM Matthew Hagan <mnhagan88@...il.com> wrote:
>>> MX64 & MX64W Hardware info:
>>>   - CPU: Broadcom BCM58625 Cortex A9 @ 1200Mhz
>>>   - RAM: 2 GB (4 x 4Gb SK Hynix H5TC4G83CFR)
>>>   - Storage: 1 GB (Micron MT29F8G08ABACA)
>>>   - Networking: BCM58625 internal switch (5x 1GbE ports)
>>>   - USB: 1x USB2.0
>>>   - Serial: Internal header
>>>   - WLAN(MX64W only): 2x Broadcom BCM43520KMLG on the PCI bus
>>>
>>> This patch adds the Meraki MX64 series-specific bindings. Since some
>>> devices make use of the older A0 SoC, changes need to be made to
>>> accommodate this case, including removal of coherency options and
>>> modification to the secondary-boot-reg.
>>>
>>> Signed-off-by: Matthew Hagan <mnhagan88@...il.com>
>> Removing the dma-coherent flags in the dts file seemed really odd until
>> I read the text above. It would seem more logical to me to have a .dtsi file
>> that has all the a0 revision specific changes, and include that from the
>> dts file.
> 
> How about having separate bcm-nsp-ax and bcm-nsp-bx dtsi files with the
> appropriate secondary-boot-reg and dma-coherent (or lack of)
> properties, which then include bcm-nsp.dtsi. Thus we can also avoid use
> of /delete-property/. Would this be preferable?

Is there any way that the Ax platforms could use a small shim between
the boot loader and the kernel which could all of the necessary DT
adaptation so the kernel only contains a single Device Tree source?

Using something like this:

https://github.com/zonque/pxa-impedance-matcher/

could be useful.

> 
>>
>> On the other hand, the /chosen, /aliases and  /memory nodes that you have
>> in the .dtsi file should probably get moved into the .dts files, as these tend
>> to be board specific settings, even if the examples you have are all
>> the same.
> 
> I did not come across any convention regarding this, though there are
> plenty of cases where the /chosen, /aliases and /memory nodes are
> defined in a .dtsi file and used by multiple similar boards. Also note
> in this case /aliases is defined in bcm-nsp.dtsi, not by me. Would we
> not prefer to avoid having 6x duplication?
> 
>>        Arnd
>>
> Matthew
> 


-- 
Florian