linux-kernel - Re: [PATCH v3 4/4] tpm_tis: Resend command to recover from data transfer errors

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Message-ID: <d380ea85b375c861067d01a2561150039e8c3491.camel@kernel.org>
Date:   Mon, 10 Jul 2023 20:00:29 +0300
From:   Jarkko Sakkinen <jarkko@...nel.org>
To:     Alexander Steffen <Alexander.Steffen@...ineon.com>,
        linux-integrity@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 4/4] tpm_tis: Resend command to recover from data
 transfer errors

On Tue, 2023-06-13 at 20:02 +0200, Alexander Steffen wrote:
> Similar to the transmission of TPM responses, also the transmission of TPM
> commands may become corrupted. Instead of aborting when detecting such
> issues, try resending the command again.
> 
> Signed-off-by: Alexander Steffen <Alexander.Steffen@...ineon.com>
> ---
>  drivers/char/tpm/tpm_tis_core.c | 13 ++++++++++---
>  1 file changed, 10 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
> index a6d1396413a7..7b13ad4bd6dd 100644
> --- a/drivers/char/tpm/tpm_tis_core.c
> +++ b/drivers/char/tpm/tpm_tis_core.c
> @@ -532,10 +532,17 @@ static int tpm_tis_send_main(struct tpm_chip *chip, const u8 *buf, size_t len)
>  	int rc;
>  	u32 ordinal;
>  	unsigned long dur;
> +	unsigned int try;
>  
> -	rc = tpm_tis_send_data(chip, buf, len);
> -	if (rc < 0)
> -		return rc;
> +	for (try = 0; try < TPM_RETRY; try++) {
> +		rc = tpm_tis_send_data(chip, buf, len);
> +		if (rc >= 0)
> +			/* Data transfer done successfully */
> +			break;
> +		else if (rc != -EIO)
> +			/* Data transfer failed, not recoverable */
> +			return rc;
> +	}
>  
>  	/* go and do it */
>  	rc = tpm_tis_write8(priv, TPM_STS(priv->locality), TPM_STS_GO);

Reviewed-by: Jarkko Sakkinen <jarkko@...nel.org>

BR, Jarkko