linux-kernel - Re: [PATCH v6 6/7] dt-bindings: tpm: Add YAML schema for TPM TIS I2C options

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Date:   Wed, 22 Apr 2020 08:15:52 +0000
From:   Amir Mizinski <amirmizi6@...il.com>
To:     Rob Herring <robh@...nel.org>
Cc:     Eyal.Cohen@...oton.com, jarkko.sakkinen@...ux.intel.com,
        oshrialkoby85@...il.com, alexander.steffen@...ineon.com,
        mark.rutland@....com, peterhuewe@....de, jgg@...pe.ca,
        arnd@...db.de, gregkh@...uxfoundation.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-integrity@...r.kernel.org, oshri.alkoby@...oton.com,
        tmaimon77@...il.com, gcwilson@...ibm.com, kgoldman@...ibm.com,
        Dan.Morav@...oton.com, oren.tanami@...oton.com,
        shmulik.hager@...oton.com, amir.mizinski@...oton.com
Subject: Re: [PATCH v6 6/7] dt-bindings: tpm: Add YAML schema for TPM TIS I2C
 options


On 2020-04-15 15:20, Rob Herring wrote:
> On Tue, Apr 07, 2020 at 07:20:43PM +0300, amirmizi6@...il.com wrote:
>> From: Amir Mizinski <amirmizi6@...il.com>
>>
>> Added a YAML schema to support tpm tis i2c realted dt-bindings for the I2c
>> PTP based physical layer.
>>
>> This patch adds the documentation for corresponding device tree bindings of
>> I2C based Physical TPM.
>> Refer to the 'I2C Interface Definition' section in
>> 'TCG PC Client PlatformTPMProfile(PTP) Specification' publication
>> for specification.
>>
>> Signed-off-by: Amir Mizinski <amirmizi6@...il.com>
>> ---
>>  .../bindings/security/tpm/tpm-tis-i2c.yaml         | 47 ++++++++++++++++++++++
>>  1 file changed, 47 insertions(+)
>>  create mode 100644 Documentation/devicetree/bindings/security/tpm/tpm-tis-i2c.yaml
>>
>> diff --git a/Documentation/devicetree/bindings/security/tpm/tpm-tis-i2c.yaml b/Documentation/devicetree/bindings/security/tpm/tpm-tis-i2c.yaml
>> new file mode 100644
>> index 0000000..13d7c2c
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/security/tpm/tpm-tis-i2c.yaml
>> @@ -0,0 +1,47 @@
>> +# SPDX-License-Identifier: GPL-2.0
>> +%YAML 1.2
>> +---
>> +$id: http://devicetree.org/schemas/security/tpm/tpm-tis-i2c.yaml#
>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>> +
>> +title: I2C PTP based TPM Device Tree Bindings
>> +
>> +maintainers:
>> +  - Amir Mizinski <amirmizi6@...il.com>
>> +
>> +description:
>> +  Device Tree Bindings for I2C based Trusted Platform Module(TPM).
>> +
>> +properties:
>> +  compatible:
>> +    contains:
>> +      const: tcg,tpm-tis-i2c
>
> This is not sufficient. I assume you are testing on some specific TPM
> chip.
>

I am, but this implementation follows the "TCG PC client Device Driver Design Principles for TPM 2.0"
It's not meant solely for out chip.

>> +
>> +  reg:
>> +    maxItems: 1
>> +
>> +  interrupt:
>> +    maxItems: 1
>> +
>> +  crc-checksum:
>> +    $ref: /schemas/types.yaml#/definitions/flag
>> +    description:
>> +      CRC checksum enable.
>
> Why would you not want CRC? Some chips support and some don't? If so,
> the compatible for the chip should imply that.
>

There's an Enable/Disable CRC option in the TPM chip, not all vendors
use this by default.

>> +
>> +required:
>> +  - compatible
>> +  - reg
>> +
>> +examples:
>> +  - |
>> +    i2c {
>> +      #address-cells = <1>;
>> +      #size-cells = <0>;
>> +
>> +      tpm-tis-i2c@2e {
>
> tpm@2e
>

I understand why i should remove "i2c", but i think it should be "tpm_tis@2e".
Respectively with "tpm_tis_spi.txt" and "tpm_tis_mmio.txt".

>> +        compatible = "tcg,tpm-tis-i2c";
>> +        reg = <0x2e>;
>> +        crc-checksum;
>> +      };
>> +    };
>> +...
>> --
>> 2.7.4
>>

Thank you for your feedback.
Best regards,
Amir Mizinski