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List:       linaro-boot-architecture
Subject:    DT conformance and "reg" tuples
From:       François_Ozog <francois.ozog () linaro ! org>
Date:       2020-12-24 10:08:48
Message-ID: CAHFG_=UntFRD3RyLP=4bGFRMAcsKH4=tA5udKgo12MF=E+j1YQ () mail ! gmail ! com
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Hi,

As I am thinking about conformance testing for SystemReady and Trusted
Substrate, I'd like to get your feedback on the following.

There are 7 values in the reg entry of interrupt-controller@210000 from the
below DT. This corresponds to 3 valid {address,size} plus a single
{address}.

The spec does not state anything on incomplete {address,size} pairs... I
understand that #size-cell can be zero, indicating that the reg will
contain only {address} "tuples" and not {address,size} tuples. But that
should be for all reg tuples, not just one.

In this case, I assume the driver will get what it wants, but from a
certification perspective:

   - I would reject this DT.
   - I would document proper tuple forming in the spec (no incomplete pairs)


Last, I would also add some "notes" in the spec about where to get the
"#*-cells" for the reg property of a device. If you think "hardware" it is
obvious that the information must be retrieved from the immediate parent
and "inheritance" does not make sense. But as I Googled the topic, I have
seen a number of discussions and wrong patches around that. So I would add
a non normative text (properly identified as such) to describe that in the
spec.

Thank you for your help

Cheers

FF
config-space@f0000000 {
    #address-cells = <0x01>;
    #size-cells = <0x01>;
    compatible = "simple-bus";
    ranges = <0x00 0x00 0xf0000000 0x1000000>;

    interrupt-controller@210000 {
       compatible = "arm,gic-400";
       #interrupt-cells = <0x03>;
       #address-cells = <0x01>;
       #size-cells = <0x01>;
       ranges;
       interrupt-controller;
       interrupts = <0x01 0x09 0xf04>;
       reg = <0x210000 0x10000 0x220000 0x20000 0x240000 0 0x20000>;
       phandle = <0x01>;

       v2m@280000 {
           compatible = "arm,gic-v2m-frame";
           msi-controller;
           reg = <0x280000 0x1000>;
           arm,msi-base-spi = <0xa0>;
           arm,msi-num-spis = <0x20>;
           phandle = <0x03>;
       };


-- 
François-Frédéric Ozog | *Director Linaro Edge & Fog Computing Group*
T: +33.67221.6485
francois.ozog@linaro.org | Skype: ffozog
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