linux-kernel - Re: [PATCH v2 1/2] dt-bindings: stm32: Add bindings for Extended TrustZone Protection

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Date:   Thu, 1 Mar 2018 15:09:00 +0100
From:   Benjamin Gaignard <benjamin.gaignard@...aro.org>
To:     Mark Rutland <mark.rutland@....com>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        Robin Murphy <robin.murphy@....com>,
        Arnd Bergmann <arnd@...db.de>,
        Loic PALLARDY <loic.pallardy@...com>,
        devicetree@...r.kernel.org,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Benjamin Gaignard <benjamin.gaignard@...com>
Subject: Re: [PATCH v2 1/2] dt-bindings: stm32: Add bindings for Extended
 TrustZone Protection

2018-03-01 15:03 GMT+01:00 Mark Rutland <mark.rutland@....com>:
> On Thu, Mar 01, 2018 at 02:58:05PM +0100, Benjamin Gaignard wrote:
>> Extended TrustZone Protection driver is very basic and only needs
>> to know where are the registers (no clock, no interrupt)
>>
>> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@...com>
>> ---
>>  .../bindings/arm/stm32/st,stm32mp1-etzpc.txt       | 25 ++++++++++++++++++++++
>>  1 file changed, 25 insertions(+)
>>  create mode 100644 Documentation/devicetree/bindings/arm/stm32/st,stm32mp1-etzpc.txt
>>
>> diff --git a/Documentation/devicetree/bindings/arm/stm32/st,stm32mp1-etzpc.txt b/Documentation/devicetree/bindings/arm/stm32/st,stm32mp1-etzpc.txt
>> new file mode 100644
>> index 000000000000..9407e37f7d15
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/arm/stm32/st,stm32mp1-etzpc.txt
>> @@ -0,0 +1,25 @@
>> +STMicroelectronics STM32 Extended TrustZone Protection driver
>> +
>> +Required properties:
>> + - compatible : value should be "st,stm32mp1-etzpc"
>> + - reg : physical base address of the IP registers and length of memory
>> +      mapped region.
>> + - protected-devices: list of phandle of devices protected by etzpc.
>> +                   Because etzpc driver rely on the phandle index in
>> +                   the list, holes must be filled with a disabled node.
>
> ... where the index corresponds to what, exactly?

to the offset of the status bits in the register

>
> Padding with a disabled node seems very hacky.

If a device node doesn't exist in the DT I need to fill the hole by something
to keep the index valid.

>
> Thanks,
> Mark.
>
>> +
>> +Example for stm32mp1:
>> +
>> +reserved: disabled_node {
>> +     status = "disabled";
>> +};
>> +
>> +etzpc: etzpc@...07000 {
>> +     compatible = "st,stm32mp1-etzpc";
>> +     reg = <0x5c007000 0x400>;
>> +             protected-devices = <&usart1>,
>> +                                 <&spi6>,
>> +                                 <&i2c4>,
>> +                                 <&reserved>,
>> +                                 <&rng1>;
>> +};
>> --
>> 2.15.0
>>