linux-kernel - Re: [PATCH v1 4/5] dt-bindings: tpm: Add the TPM TIS I2C device tree binding documentaion

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Date:   Thu, 14 Nov 2019 13:10:54 -0600
From:   Rob Herring <robh@...nel.org>
To:     amirmizi6@...il.com
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,
        ayna@...ux.vnet.ibm.com, Dan.Morav@...oton.com,
        oren.tanami@...oton.com, shmulik.hagar@...oton.com,
        amir.mizinski@...oton.com
Subject: Re: [PATCH v1 4/5] dt-bindings: tpm: Add the TPM TIS I2C device tree
 binding documentaion

On Sun, Nov 10, 2019 at 06:21:36PM +0200, amirmizi6@...il.com wrote:
> From: Amir Mizinski <amirmizi6@...il.com>
> 
> this file aim at documenting TPM TIS I2C related dt-bindings for the I2C PTP based Physical TPM.
> 
> Signed-off-by: Amir Mizinski <amirmizi6@...il.com>
> ---
>  .../bindings/security/tpm/tpm_tis_i2c.txt          | 24 ++++++++++++++++++++++
>  1 file changed, 24 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/security/tpm/tpm_tis_i2c.txt

Please make this a schema. See 
Documentation/devicetree/writing-schema.rst.

> 
> diff --git a/Documentation/devicetree/bindings/security/tpm/tpm_tis_i2c.txt b/Documentation/devicetree/bindings/security/tpm/tpm_tis_i2c.txt
> new file mode 100644
> index 0000000..7d5a69e
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/security/tpm/tpm_tis_i2c.txt
> @@ -0,0 +1,24 @@
> +* Device Tree Bindings for I2C PTP based Trusted Platform Module(TPM)
> +
> +The TCG defines hardware protocol, registers and interface (based
> +on the TPM Interface Specification) for accessing TPM devices
> +implemented with an I2C interface.
> +
> +Refer to the 'I2C Interface Definition' section in 'TCG PC Client
> +PlatformTPMProfile(PTP) Specification' publication for specification.
> +
> +Required properties:
> +
> +- compatible     : Should be "tcg,tpm_tis-i2c"

s/_/-/

As this has to be under an I2C controller node, the '-i2c' part is 
redundant.

There's a bigger issue that the h/w here is more than just an I2C 
protocol. The chip may have multiple power supplies, clocks, reset 
lines, etc. HID over I2C seems like a similar case. Does the spec define 
*all* of that? If not, you need chip specific compatibles. You can keep 
this as a fallback though.

> +- reg            : Address on the bus
> +- tpm-pirq       : Input gpio pin, used for host interrupts

GPIO connections are properties ending in '-gpios'. However, if the only 
use is an interrupt, then you should use 'interrupts'.

> +
> +Example (for Raspberry Pie 3 Board with Nuvoton's NPCT75X (2.0)
> +-------------------------------------------------------------------
> +
> +tpm_tis-i2c: tpm_tis-i2c@2e {
> +
> +       compatible = "tcg,tpm_tis-i2c";
> +       reg = <0x2e>;
> +       tpm-pirq = <&gpio 24 GPIO_ACTIVE_HIGH>;
> +};
> -- 
> 2.7.4
>