linux-kernel - Re: [PATCH v4 1/3] dt-bindings: trivial-devices: Add two I2C TPM devices

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Date:   Thu, 2 Jun 2022 17:34:07 +0200
From:   Alexander Steffen <Alexander.Steffen@...ineon.com>
To:     Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
CC:     <jarkko@...nel.org>, <linux-kernel@...r.kernel.org>,
        <linux-integrity@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <peterhuewe@....de>, <jgg@...pe.ca>,
        <krzysztof.kozlowski+dt@...aro.org>,
        Johannes Holland <johannes.holland@...ineon.com>,
        Amir Mizinski <amirmizi6@...il.com>
Subject: Re: [PATCH v4 1/3] dt-bindings: trivial-devices: Add two I2C TPM
 devices

On 02.06.22 15:48, Rob Herring wrote:
> On Thu, May 26, 2022 at 02:29:56PM +0200, Krzysztof Kozlowski wrote:
>> On 25/05/2022 18:58, Alexander Steffen wrote:
>>> Both are supported by the upcoming tpm_tis_i2c driver.
>>>
>>> Signed-off-by: Alexander Steffen <Alexander.Steffen@...ineon.com>
>>> ---
>>>   Documentation/devicetree/bindings/trivial-devices.yaml | 4 ++++
>>>   1 file changed, 4 insertions(+)
>>>
>>> diff --git a/Documentation/devicetree/bindings/trivial-devices.yaml b/Documentation/devicetree/bindings/trivial-devices.yaml
>>> index 550a2e5c9e05..dc52822331dd 100644
>>> --- a/Documentation/devicetree/bindings/trivial-devices.yaml
>>> +++ b/Documentation/devicetree/bindings/trivial-devices.yaml
>>> @@ -135,6 +135,8 @@ properties:
>>>             - infineon,slb9635tt
>>>               # Infineon SLB9645 I2C TPM (new protocol, max 400khz)
>>>             - infineon,slb9645tt
>>> +            # Infineon SLB9673 I2C TPM 2.0
>>> +          - infineon,slb9673
>>>               # Infineon TLV493D-A1B6 I2C 3D Magnetic Sensor
>>>             - infineon,tlv493d-a1b6
>>>               # Infineon Multi-phase Digital VR Controller xdpe11280
>>> @@ -323,6 +325,8 @@ properties:
>>>             - st,24c256
>>>               # Ambient Light Sensor with SMBUS/Two Wire Serial Interface
>>>             - taos,tsl2550
>>> +            # TCG TIS-compliant TPM with I2C interface
>>> +          - tcg,tpm_tis-i2c
>>
>> One flavor uses tpm-tis, another tpm_tis... I guess it is too late to
>> make it consistent, but let's stick to the one more reasonable, so:
>> "tpm-tis-i2c".
> 
> Neither should be used except perhaps as a fallback.

That is the intention, yes.

> Does 'TCG TIS-compliant TPM' encompass every property of a device? Power
> supplies, resets, interrupts, quirks, etc.?

In an ideal world, yes. In practice, of course implementations do have 
bugs that might require different workarounds. By selecting 
tcg,tpm-tis-i2c instead of anything more specific, you promise that the 
device is fully compliant to the TCG specification and does not require 
any such workarounds.

Alexander