linux-kernel - Re: [PATCH v2] tpm: Add flag to use default cancellation policy

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Date:   Mon, 14 Nov 2022 03:17:59 +0000
From:   Joel Stanley <joel@....id.au>
To:     Eddie James <eajames@...ux.ibm.com>
Cc:     linux-integrity@...r.kernel.org, linux-kernel@...r.kernel.org,
        peterhuewe@....de, jarkko@...nel.org, jgg@...pe.ca
Subject: Re: [PATCH v2] tpm: Add flag to use default cancellation policy

On Mon, 7 Nov 2022 at 17:14, Eddie James <eajames@...ux.ibm.com> wrote:
>
> The check for cancelled request depends on the VID of the chip, but
> some chips share VID which shouldn't share their cancellation
> behavior. This is the case for the Nuvoton NPCT75X, which should use
> the default cancellation check, not the Winbond one.
> To avoid changing the existing behavior, add a new flag to indicate
> that the chip should use the default cancellation check and set it
> for the I2C TPM2 TIS driver.
>
> Signed-off-by: Eddie James <eajames@...ux.ibm.com>

Tested-by: Joel Stanley <joel@....id.au>
Fixes: bbc23a07b072 ("tpm: Add tpm_tis_i2c backend for tpm_tis_core")

With this patch, and "tpm: tis_i2c: Fix sanity check interrupt enable
mask", and the extra compatible strings the driver correctly probes on
boot with the Nuvoton part.


> ---
> Changes since v1:
>  - Update switch statement with default: break;
>
>  drivers/char/tpm/tpm_tis_core.c | 20 ++++++++++++--------
>  drivers/char/tpm/tpm_tis_core.h |  1 +
>  drivers/char/tpm/tpm_tis_i2c.c  |  1 +
>  3 files changed, 14 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
> index 757623bacfd5..3f98e587b3e8 100644
> --- a/drivers/char/tpm/tpm_tis_core.c
> +++ b/drivers/char/tpm/tpm_tis_core.c
> @@ -682,15 +682,19 @@ static bool tpm_tis_req_canceled(struct tpm_chip *chip, u8 status)
>  {
>         struct tpm_tis_data *priv = dev_get_drvdata(&chip->dev);
>
> -       switch (priv->manufacturer_id) {
> -       case TPM_VID_WINBOND:
> -               return ((status == TPM_STS_VALID) ||
> -                       (status == (TPM_STS_VALID | TPM_STS_COMMAND_READY)));
> -       case TPM_VID_STM:
> -               return (status == (TPM_STS_VALID | TPM_STS_COMMAND_READY));
> -       default:
> -               return (status == TPM_STS_COMMAND_READY);
> +       if (!test_bit(TPM_TIS_DEFAULT_CANCELLATION, &priv->flags)) {
> +               switch (priv->manufacturer_id) {
> +               case TPM_VID_WINBOND:
> +                       return ((status == TPM_STS_VALID) ||
> +                               (status == (TPM_STS_VALID | TPM_STS_COMMAND_READY)));
> +               case TPM_VID_STM:
> +                       return (status == (TPM_STS_VALID | TPM_STS_COMMAND_READY));
> +               default:
> +                       break;
> +               }
>         }
> +
> +       return status == TPM_STS_COMMAND_READY;
>  }
>
>  static irqreturn_t tis_int_handler(int dummy, void *dev_id)
> diff --git a/drivers/char/tpm/tpm_tis_core.h b/drivers/char/tpm/tpm_tis_core.h
> index 66a5a13cd1df..b68479e0de10 100644
> --- a/drivers/char/tpm/tpm_tis_core.h
> +++ b/drivers/char/tpm/tpm_tis_core.h
> @@ -86,6 +86,7 @@ enum tis_defaults {
>  enum tpm_tis_flags {
>         TPM_TIS_ITPM_WORKAROUND         = BIT(0),
>         TPM_TIS_INVALID_STATUS          = BIT(1),
> +       TPM_TIS_DEFAULT_CANCELLATION    = BIT(2),
>  };
>
>  struct tpm_tis_data {
> diff --git a/drivers/char/tpm/tpm_tis_i2c.c b/drivers/char/tpm/tpm_tis_i2c.c
> index 45f388127f4b..91451ee1ef8d 100644
> --- a/drivers/char/tpm/tpm_tis_i2c.c
> +++ b/drivers/char/tpm/tpm_tis_i2c.c
> @@ -329,6 +329,7 @@ static int tpm_tis_i2c_probe(struct i2c_client *dev,
>         if (!phy->io_buf)
>                 return -ENOMEM;
>
> +       set_bit(TPM_TIS_DEFAULT_CANCELLATION, &phy->priv.flags);
>         phy->i2c_client = dev;
>
>         /* must precede all communication with the tpm */
> --
> 2.31.1
>