[OpenWrt-Devel] [PATCH 2/2 v3] linux: add support of Synopsys ARC770-based boards

[Jonas Gorski]

Hi Alexey,

On Thu, Nov 5, 2015 at 7:14 PM, Alexey Brodkin
<Alexey.Brodkin at synopsys.com> wrote:
> Hi Jonas,
>
> On Wed, 2015-11-04 at 20:22 +0300, Alexey Brodkin wrote:
>> Hi Jonas,
>>
>> On Wed, 2015-11-04 at 13:06 +0100, Jonas Gorski wrote:
>> > Hi,
>> >
>> > On Tue, Nov 3, 2015 at 12:27 AM, Alexey Brodkin
>> > <Alexey.Brodkin at synopsys.com> wrote:
>> > > +       ;;
>> > > +esac
>> > > +
>> > > +uci commit network
>> > > +
>> > > +exit 0
>> > > diff --git a/target/linux/arc770/base-files/lib/arc.sh b/target/linux/arc770/base-files/lib/arc.sh
>> > > new file mode 100644
>> > > index 0000000..b15e94b
>> > > --- /dev/null
>> > > +++ b/target/linux/arc770/base-files/lib/arc.sh
>> > > @@ -0,0 +1,76 @@
>> > > +#!/bin/sh
>> > > +#
>> > > +# Copyright (C) 2015 OpenWrt.org
>> > > +#
>> > > +
>> > > +# defaults
>> > > +ARC_BOARD_NAME="generic"
>> > > +ARC_BOARD_MODEL="Generic arc board"
>> > > +
>> > > +arc_board_detect() {
>> > > +       local board
>> > > +       local model
>> > > +
>> > > +       [ -e "/tmp/sysinfo/" ] || mkdir -p "/tmp/sysinfo/"
>> > > +
>> > > +       model="$( cat /proc/device-tree/compatible )"
>> > > +
>> > > +       # We cannot just use "model" as it is because in case of SDP board
>> >
>> > ePAPR says your dts root nodes must have a "model" property that
>> > uniquely identifies the board. I see that is currently missing even in
>> > upstream, so please fix your dts files. Then you won't need to grep in
>> > the compatible. On a side node, ePAPR also says that the recommended
>> > format is the same as compatible but .. *looks at arm* .. apparently
>> > nobody does that.
>>
>> Indeed "model" is a required property.
>> So thanks for that suggestion.
>>
>> Then we'll have:
>> ---------------->8------------------
>> compatible = "snps,arc-sdp";
>> model = "snps,axs101";

Grepping through the different arch's dts directories, some arches use
compatible like model values (e.g. powerpc), some use free text values
(e.g. arm). Might be something discuss worthy for devicetree ML how
this spec "violation" should be handled. Especially since the example
in Documentation/devicetree/usage-model.txt doesn't have one.

>> ---------------->8------------------
>> which looks for sure much better!
>>
>> Will do this for starters here in OpenWRT and will submit a patch upstream
>> in Linux kernel.
>
> I started to think about it and now I understand why we use complicated
> "compatible" value.
>
> This allows us to use multiple platform-specific parts at once.
> We use "snps,arc-sdp" here:
> http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/arch/arc/kernel/devtree.c#n35
> and "snps,axs101" here:
> http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/arch/arc/plat-axs10x/axs10x.c#n464
>
> In the first case it's not really necessary to use "compatible" node but
> it's usage is quite convenient, see we only need to execute this oneliner:
> -------------------->8----------------------
> of_flat_dt_is_compatible(dt_root, "snps,arc-sdp")
> -------------------->8----------------------
>
> But if we use "model" node instead we'll need to do:
> 1) of_get_property
> 2) strcmp
>
> This is a bit longer, still possible solution.
>
> So even though your proposal is very useful and I'm going to discuss it
> with Vineet Gupta (ARC Linux maintainer) but if you don't mind I'd go
> without that change for this submission. Then if your proposal is implemented
> I'll need to rework OpenWRT scripts anyways because newer upstream kernel
> will require that.
>
> Are you OK with that?

My suggestion was only for the model detection script part, not to
modify anything in the kernel (apart from adding a model property to
the dts files). The kernel should just keep using the compatible
property as it properly handles multiple compatible names etc, and it
doesn't need to be unique.


Jonas
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