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

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Date:   Thu, 14 Apr 2022 15:08:10 +0300
From:   Jarkko Sakkinen <jarkko@...nel.org>
To:     Paul Menzel <pmenzel@...gen.mpg.de>
Cc:     "Jes B. Klinke" <jbk@...omium.org>,
        linux-integrity@...r.kernel.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

On Thu, Apr 07, 2022 at 12:21:44PM +0200, Paul Menzel wrote:
> 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

OK, these are legit suggestions. Paul, can you do these changes and add my
reviewed-by for the +1 version?

BR, Jarkko