Re: [PATCH] tpm, tpm_tis: Workaround failed command reception on Infineon devices

[Jarkko Sakkinen <jarkko@kernel.org>]

On Thu, Mar 06, 2025 at 09:00:56AM +0000, Jonathan McDowell wrote:
> From: Jonathan McDowell <noodles@meta.com>
> 
> Some Infineon devices have a issue where the status register will get
> stuck with a quick REQUEST_USE / COMMAND_READY sequence. This is not
> simply a matter of requiring a longer timeout; the work around is to
> retry the command submission. Add appropriate logic to do this in the
> send path.
> 
> This is fixed in later firmware revisions, but those are not always
> available, and cannot generally be easily updated from outside a
> firmware environment.
> 
> Testing has been performed with a simple repeated loop of doing a
> TPM2_CC_GET_CAPABILITY for TPM_CAP_PROP_MANUFACTURER using the Go code
> at:
> 
>  https://the.earth.li/~noodles/tpm-stuff/timeout-reproducer-simple.go
> 
> It can take several hours to reproduce, and millions of operations.
> 
> Signed-off-by: Jonathan McDowell <noodles@meta.com>
> ---
>  drivers/char/tpm/tpm_tis_core.c | 17 ++++++++++++++---
>  drivers/char/tpm/tpm_tis_core.h |  1 +
>  include/linux/tpm.h             |  1 +
>  3 files changed, 16 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
> index 167d71747666..e4eae206a353 100644
> --- a/drivers/char/tpm/tpm_tis_core.c
> +++ b/drivers/char/tpm/tpm_tis_core.c
> @@ -464,7 +464,10 @@ static int tpm_tis_send_data(struct tpm_chip *chip, const u8 *buf, size_t len)
>  
>  		if (wait_for_tpm_stat(chip, TPM_STS_VALID, chip->timeout_c,
>  					&priv->int_queue, false) < 0) {
> -			rc = -ETIME;
> +			if (test_bit(TPM_TIS_STATUS_WORKAROUND, &priv->flags))
> +				rc = -EAGAIN;
> +			else
> +				rc = -ETIME;
>  			goto out_err;
>  		}
>  		status = tpm_tis_status(chip);
> @@ -481,7 +484,10 @@ static int tpm_tis_send_data(struct tpm_chip *chip, const u8 *buf, size_t len)
>  
>  	if (wait_for_tpm_stat(chip, TPM_STS_VALID, chip->timeout_c,
>  				&priv->int_queue, false) < 0) {
> -		rc = -ETIME;
> +		if (test_bit(TPM_TIS_STATUS_WORKAROUND, &priv->flags))
> +			rc = -EAGAIN;
> +		else
> +			rc = -ETIME;

I'd encapsulate this inside wait_for_tpm_stat().


>  		goto out_err;
>  	}
>  	status = tpm_tis_status(chip);
> @@ -546,9 +552,11 @@ static int tpm_tis_send_main(struct tpm_chip *chip, const u8 *buf, size_t len)
>  		if (rc >= 0)
>  			/* Data transfer done successfully */
>  			break;
> -		else if (rc != -EIO)
> +		else if (rc != EAGAIN && rc != -EIO)
>  			/* Data transfer failed, not recoverable */
>  			return rc;
> +
> +		usleep_range(priv->timeout_min, priv->timeout_max);
>  	}
>  
>  	/* go and do it */
> @@ -1144,6 +1152,9 @@ int tpm_tis_core_init(struct device *dev, struct tpm_tis_data *priv, int irq,
>  		priv->timeout_max = TIS_TIMEOUT_MAX_ATML;
>  	}
>  
> +	if (priv->manufacturer_id == TPM_VID_IFX)
> +		set_bit(TPM_TIS_STATUS_WORKAROUND, &priv->flags);
> +
>  	if (is_bsw()) {
>  		priv->ilb_base_addr = ioremap(INTEL_LEGACY_BLK_BASE_ADDR,
>  					ILB_REMAP_SIZE);
> diff --git a/drivers/char/tpm/tpm_tis_core.h b/drivers/char/tpm/tpm_tis_core.h
> index 690ad8e9b731..ce97b58dc005 100644
> --- a/drivers/char/tpm/tpm_tis_core.h
> +++ b/drivers/char/tpm/tpm_tis_core.h
> @@ -89,6 +89,7 @@ enum tpm_tis_flags {
>  	TPM_TIS_INVALID_STATUS		= 1,
>  	TPM_TIS_DEFAULT_CANCELLATION	= 2,
>  	TPM_TIS_IRQ_TESTED		= 3,
> +	TPM_TIS_STATUS_WORKAROUND	= 4,

TPM_TIS_TIMEOUT_AGAIN or maybe *_REPEAT? The current name does
not tell anything.

>  };
>  
>  struct tpm_tis_data {
> diff --git a/include/linux/tpm.h b/include/linux/tpm.h
> index 20a40ade8030..6c3125300c00 100644
> --- a/include/linux/tpm.h
> +++ b/include/linux/tpm.h
> @@ -335,6 +335,7 @@ enum tpm2_cc_attrs {
>  #define TPM_VID_WINBOND  0x1050
>  #define TPM_VID_STM      0x104A
>  #define TPM_VID_ATML     0x1114
> +#define TPM_VID_IFX      0x15D1
>  
>  enum tpm_chip_flags {
>  	TPM_CHIP_FLAG_BOOTSTRAPPED		= BIT(0),
> -- 
> 2.48.1
> 

BR, Jarkko