linux-kernel - Re: [PATCH] tpm: cr50: Add new device/vendor ID 0x504a6666

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Message-ID: <6528eec1-0ab1-a5ff-3e30-2e06256dfd04@molgen.mpg.de>
Date:   Thu, 7 Apr 2022 12:21:44 +0200
From:   Paul Menzel <pmenzel@...gen.mpg.de>
To:     "Jes B. Klinke" <jbk@...omium.org>
Cc:     linux-integrity@...r.kernel.org,
        Jarkko Sakkinen <jarkko@...nel.org>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Peter Huewe <peterhuewe@....de>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] tpm: cr50: Add new device/vendor ID 0x504a6666

Dear Jes,


Thank you for your patch.

Am 05.04.22 um 19:37 schrieb Jes B. Klinke:
> Accept one additional numerical value of DID:VID for next generation
> Google TPM, to be used in future Chromebooks.

Maybe extend:

… Google TPM with new firmware …

The TPM with the new firmware has the code name TI50, and going to use 
the same interfaces.

> This patch touches more lines than may seem necessary, as a result of
> the need to move the error case to sit after the two recognized cases.
> 
> Signed-off-by: Jes B. Klinke <jbk@...omium.org>
> ---
> 
>   drivers/char/tpm/tpm_tis_i2c_cr50.c | 21 +++++++++++++--------
>   1 file changed, 13 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/char/tpm/tpm_tis_i2c_cr50.c b/drivers/char/tpm/tpm_tis_i2c_cr50.c
> index f6c0affbb4567..bf54ebd6724b0 100644
> --- a/drivers/char/tpm/tpm_tis_i2c_cr50.c
> +++ b/drivers/char/tpm/tpm_tis_i2c_cr50.c
> @@ -31,6 +31,7 @@
>   #define TPM_CR50_TIMEOUT_SHORT_MS	2		/* Short timeout during transactions */
>   #define TPM_CR50_TIMEOUT_NOIRQ_MS	20		/* Timeout for TPM ready without IRQ */
>   #define TPM_CR50_I2C_DID_VID		0x00281ae0L	/* Device and vendor ID reg value */
> +#define TPM_TI50_I2C_DID_VID		0x504a6666L	/* Device and vendor ID reg value */
>   #define TPM_CR50_I2C_MAX_RETRIES	3		/* Max retries due to I2C errors */
>   #define TPM_CR50_I2C_RETRY_DELAY_LO	55		/* Min usecs between retries on I2C */
>   #define TPM_CR50_I2C_RETRY_DELAY_HI	65		/* Max usecs between retries on I2C */
> @@ -742,16 +743,20 @@ static int tpm_cr50_i2c_probe(struct i2c_client *client)
>   	}
>   
>   	vendor = le32_to_cpup((__le32 *)buf);
> -	if (vendor != TPM_CR50_I2C_DID_VID) {
> -		dev_err(dev, "Vendor ID did not match! ID was %08x\n", vendor);
> -		tpm_cr50_release_locality(chip, true);
> -		return -ENODEV;
> +	if (vendor == TPM_CR50_I2C_DID_VID) {
> +		dev_info(dev, "cr50 TPM 2.0 (i2c 0x%02x irq %d id 0x%x)\n",
> +			 client->addr, client->irq, vendor >> 16);
> +		return tpm_chip_register(chip);
> +	}
> +	if (vendor == TPM_TI50_I2C_DID_VID) {
> +		dev_info(dev, "ti50 TPM 2.0 (i2c 0x%02x irq %d id 0x%x)\n",
> +			 client->addr, client->irq, vendor >> 16);
> +		return tpm_chip_register(chip);
>   	}

Both branches are quite similar. Can a ternary operator be used?

     dev_info(dev, "%s TPM 2.0 (i2c 0x%02x irq %d id 0x%x)\n",
     	 (vendor == TPM_CR50_I2C_DID_VID) ? "cr50" : "ti50", client->addr, 
client->irq, vendor >> 16);
     return tpm_chip_register(chip);

and the original flow be left? (A separate variable can also be added.)

>   
> -	dev_info(dev, "cr50 TPM 2.0 (i2c 0x%02x irq %d id 0x%x)\n",
> -		 client->addr, client->irq, vendor >> 16);
> -
> -	return tpm_chip_register(chip);
> +	dev_err(dev, "Vendor ID did not match! ID was %08x\n", vendor);
> +	tpm_cr50_release_locality(chip, true);
> +	return -ENODEV;
>   }
>   
>   /**


Kind regards,

Paul