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Re: [PATCH] external references for device tree overlays

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  Re: [PATCH] external references for device tree overlays Rob Herring <robh+dt@kernel.org> - 2017-06-08 00:20 +0200
    Re: [PATCH] external references for device tree overlays Stefani Seibold <stefani@seibold.net> - 2017-06-08 09:00 +0200

#1660284 — Re: [PATCH] external references for device tree overlays

On Wed, Jun 7, 2017 at 3:11 AM, Pantelis Antoniou
<pantelis.antoniou@konsulko.com> wrote:
> Hi Stefani,
>
> On Tue, 2017-06-06 at 21:17 +0200, Stefani Seibold wrote:
>> Hi Pantelis,
>>
>> thanks for the suggestion. This feature is not very well documented. I
>> tried this on my rasp1 running 4.12.0-rc3 and it doesn't work. My
>> source is:
>>
>> // rapsi example
>> /dts-v1/;
>> /plugin/;
>>
>> / {
>>     compatible = "brcm,bcm2835", "brcm,bcm2708", "brcm,bcm2709";
>>
>>     fragment@0 {
>>         target-path = "/soc/i2s@7e203000";
>>         __overlay__ {
>>             #address-cells = <0x00000001>;
>>             #size-cells = <0x00000001>;
>>             test = "test";
>>             timer = <&{/soc/timer@7e0030000}>;
>>         };
>>     };
>> };
>>
>>
>> The resulting overlay is (decompiled with fdtdump):
>>
>> /dts-v1/;
>> // magic:             0xd00dfeed
>> // totalsize:         0x19a (410)
>> // off_dt_struct:     0x38
>> // off_dt_strings:    0x148
>> // off_mem_rsvmap:    0x28
>> // version:           17
>> // last_comp_version: 16
>> // boot_cpuid_phys:   0x0
>> // size_dt_strings:   0x52
>> // size_dt_struct:    0x110
>>
>> / {
>>     compatible = "brcm,bcm2835", "brcm,bcm2708", "brcm,bcm2709";
>>     fragment@0 {
>>         target-path = "/soc/i2s@7e203000";
>>         __overlay__ {
>>             #address-cells = <0x00000001>;
>>             #size-cells = <0x00000001>;
>>             test = "test";
>>             timer = <0xdeadbeef>;
>>         };
>>     };
>>     __fixups__ {
>>         /soc/timer@7e0030000 = "/fragment@0/__overlay__:timer:0";
>>     };
>> };
>>
>> But this will not apply:
>>
>> OF: resolver: overlay phandle fixup failed: -22
>> create_overlay: Failed to resolve tree
>>
>>
>
> Yes, it will not work as it is; my point is that you don't need the
> magic __*__ node.
>
> You will need to modify the overlay application code to live insert a
> phandle (if it doesn't exist) when it encounters a /path fixup.

phandles only exist if something in the base tree refers to that node.
Adding them when they don't exist should definitely be something we
support for overlays. But don't call that a broken DT. That would be a
separate issue.

Rob

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#1660796

On Wed, 2017-06-07 at 17:19 -0500, Rob Herring wrote:
> On Wed, Jun 7, 2017 at 3:11 AM, Pantelis Antoniou
> <pantelis.antoniou@konsulko.com> wrote:
> > Hi Stefani,
> > 
> > On Tue, 2017-06-06 at 21:17 +0200, Stefani Seibold wrote:
> > > Hi Pantelis,
> > > 
> > > thanks for the suggestion. This feature is not very well
> > > documented. I
> > > tried this on my rasp1 running 4.12.0-rc3 and it doesn't work. My
> > > source is:
> > > 
> > > // rapsi example
> > > /dts-v1/;
> > > /plugin/;
> > > 
> > > / {
> > >     compatible = "brcm,bcm2835", "brcm,bcm2708", "brcm,bcm2709";
> > > 
> > >     fragment@0 {
> > >         target-path = "/soc/i2s@7e203000";
> > >         __overlay__ {
> > >             #address-cells = <0x00000001>;
> > >             #size-cells = <0x00000001>;
> > >             test = "test";
> > >             timer = <&{/soc/timer@7e0030000}>;
> > >         };
> > >     };
> > > };
> > > 
> > > 
> > > The resulting overlay is (decompiled with fdtdump):
> > > 
> > > /dts-v1/;
> > > // magic:             0xd00dfeed
> > > // totalsize:         0x19a (410)
> > > // off_dt_struct:     0x38
> > > // off_dt_strings:    0x148
> > > // off_mem_rsvmap:    0x28
> > > // version:           17
> > > // last_comp_version: 16
> > > // boot_cpuid_phys:   0x0
> > > // size_dt_strings:   0x52
> > > // size_dt_struct:    0x110
> > > 
> > > / {
> > >     compatible = "brcm,bcm2835", "brcm,bcm2708", "brcm,bcm2709";
> > >     fragment@0 {
> > >         target-path = "/soc/i2s@7e203000";
> > >         __overlay__ {
> > >             #address-cells = <0x00000001>;
> > >             #size-cells = <0x00000001>;
> > >             test = "test";
> > >             timer = <0xdeadbeef>;
> > >         };
> > >     };
> > >     __fixups__ {
> > >         /soc/timer@7e0030000 = "/fragment@0/__overlay__:timer:0";
> > >     };
> > > };
> > > 
> > > But this will not apply:
> > > 
> > > OF: resolver: overlay phandle fixup failed: -22
> > > create_overlay: Failed to resolve tree
> > > 
> > > 
> > 
> > Yes, it will not work as it is; my point is that you don't need the
> > magic __*__ node.
> > 
> > You will need to modify the overlay application code to live insert
> > a
> > phandle (if it doesn't exist) when it encounters a /path fixup.
> 
> phandles only exist if something in the base tree refers to that
> node.
> Adding them when they don't exist should definitely be something we
> support for overlays. But don't call that a broken DT. That would be
> a
> separate issue.
> 

Believe me it is broken. Due a NDA i am not able to give you more
details about the vendor. But there forgot do provide an device node
which must refer to the attached network and interrupt controller.

- Stefani

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