On Tue, 2023-06-13 at 20:02 +0200, Alexander Steffen wrote:
> TPM responses may become damaged during transmission, for example due to
> bit flips on the wire. Instead of aborting when detecting such issues, the
> responseRetry functionality can be used to make the TPM retransmit its
> response and receive it again without errors.
>
> Signed-off-by: Alexander Steffen <Alexander.Steffen@xxxxxxxxxxxx>
> ---
> drivers/char/tpm/tpm_tis_core.c | 37 ++++++++++++++++++++++++++-------
> drivers/char/tpm/tpm_tis_core.h | 1 +
> 2 files changed, 30 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
> index 5ddaf24518be..a6d1396413a7 100644
> --- a/drivers/char/tpm/tpm_tis_core.c
> +++ b/drivers/char/tpm/tpm_tis_core.c
> @@ -337,7 +337,7 @@ static int recv_data(struct tpm_chip *chip, u8 *buf, size_t count)
> return size;
> }
>
> -static int tpm_tis_recv(struct tpm_chip *chip, u8 *buf, size_t count)
> +static int tpm_tis_try_recv(struct tpm_chip *chip, u8 *buf, size_t count)
> {
> struct tpm_tis_data *priv = dev_get_drvdata(&chip->dev);
> int size = 0;
> @@ -345,11 +345,6 @@ static int tpm_tis_recv(struct tpm_chip *chip, u8 *buf, size_t count)
> u32 expected;
> int rc;
>
> - if (count < TPM_HEADER_SIZE) {
> - size = -EIO;
> - goto out;
> - }
> -
> size = recv_data(chip, buf, TPM_HEADER_SIZE);
> /* read first 10 bytes, including tag, paramsize, and result */
> if (size < TPM_HEADER_SIZE) {
> @@ -382,7 +377,7 @@ static int tpm_tis_recv(struct tpm_chip *chip, u8 *buf, size_t count)
> goto out;
> }
> status = tpm_tis_status(chip);
> - if (status & TPM_STS_DATA_AVAIL) { /* retry? */
> + if (status & TPM_STS_DATA_AVAIL) {
> dev_err(&chip->dev, "Error left over data\n");
> size = -EIO;
> goto out;
> @@ -396,10 +391,36 @@ static int tpm_tis_recv(struct tpm_chip *chip, u8 *buf, size_t count)
> }
>
> out:
> - tpm_tis_ready(chip);
> return size;
> }
>
> +static int tpm_tis_recv(struct tpm_chip *chip, u8 *buf, size_t count)
> +{
> + struct tpm_tis_data *priv = dev_get_drvdata(&chip->dev);
> + unsigned int try;
> + int rc = 0;
> +
> + if (count < TPM_HEADER_SIZE)
> + return -EIO;
> +
> + for (try = 0; try < TPM_RETRY; try++) {
> + rc = tpm_tis_try_recv(chip, buf, count);
> +
> + if (rc == -EIO)
> + /* Data transfer errors, indicated by EIO, can be
> + * recovered by rereading the response.
> + */
> + tpm_tis_write8(priv, TPM_STS(priv->locality),
> + TPM_STS_RESPONSE_RETRY);
> + else
> + break;
> + }
> +
> + tpm_tis_ready(chip);
> +
> + return rc;
> +}
> +
> /*
> * If interrupts are used (signaled by an irq set in the vendor structure)
> * tpm.c can skip polling for the data to be available as the interrupt is
> diff --git a/drivers/char/tpm/tpm_tis_core.h b/drivers/char/tpm/tpm_tis_core.h
> index 610bfadb6acf..3a6b600d22ba 100644
> --- a/drivers/char/tpm/tpm_tis_core.h
> +++ b/drivers/char/tpm/tpm_tis_core.h
> @@ -34,6 +34,7 @@ enum tis_status {
> TPM_STS_GO = 0x20,
> TPM_STS_DATA_AVAIL = 0x10,
> TPM_STS_DATA_EXPECT = 0x08,
> + TPM_STS_RESPONSE_RETRY = 0x02,
> TPM_STS_READ_ZERO = 0x23, /* bits that must be zero on read */
> };
>
Reviewed-by: Jarkko Sakkinen <jarkko@xxxxxxxxxx>
BR, Jarkko
