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Subject[PATCH v6 2/3] tpm: Add tpm_tis_verify_crc to the tpm_tis_phy_ops protocol layer
Date
Some TPMs, e.g. those implementing the I2C variant of TIS, can verify
data transfers to/from the FIFO with a CRC. The CRC is calculated over
the entirety of the FIFO register. Since the phy_ops layer is not aware
when the core layer is done reading/writing the FIFO, CRC verification
must be triggered from the core layer. To this end, add an optional
phy_ops API call.

Co-developed-by: Johannes Holland <johannes.holland@infineon.com>
Signed-off-by: Johannes Holland <johannes.holland@infineon.com>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Alexander Steffen <Alexander.Steffen@infineon.com>
---
drivers/char/tpm/tpm_tis_core.c | 14 ++++++++++++++
drivers/char/tpm/tpm_tis_core.h | 10 ++++++++++
2 files changed, 24 insertions(+)

diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
index dc56b976d816..757623bacfd5 100644
--- a/drivers/char/tpm/tpm_tis_core.c
+++ b/drivers/char/tpm/tpm_tis_core.c
@@ -289,6 +289,7 @@ static int tpm_tis_recv(struct tpm_chip *chip, u8 *buf, size_t count)
int size = 0;
int status;
u32 expected;
+ int rc;

if (count < TPM_HEADER_SIZE) {
size = -EIO;
@@ -328,6 +329,13 @@ static int tpm_tis_recv(struct tpm_chip *chip, u8 *buf, size_t count)
goto out;
}

+ rc = tpm_tis_verify_crc(priv, (size_t)size, buf);
+ if (rc < 0) {
+ dev_err(&chip->dev, "CRC mismatch for response.\n");
+ size = rc;
+ goto out;
+ }
+
out:
tpm_tis_ready(chip);
return size;
@@ -443,6 +451,12 @@ static int tpm_tis_send_main(struct tpm_chip *chip, const u8 *buf, size_t len)
if (rc < 0)
return rc;

+ rc = tpm_tis_verify_crc(priv, len, buf);
+ if (rc < 0) {
+ dev_err(&chip->dev, "CRC mismatch for command.\n");
+ return rc;
+ }
+
/* go and do it */
rc = tpm_tis_write8(priv, TPM_STS(priv->locality), TPM_STS_GO);
if (rc < 0)
diff --git a/drivers/char/tpm/tpm_tis_core.h b/drivers/char/tpm/tpm_tis_core.h
index 6c203f36b8a1..66a5a13cd1df 100644
--- a/drivers/char/tpm/tpm_tis_core.h
+++ b/drivers/char/tpm/tpm_tis_core.h
@@ -121,6 +121,8 @@ struct tpm_tis_phy_ops {
u8 *result, enum tpm_tis_io_mode mode);
int (*write_bytes)(struct tpm_tis_data *data, u32 addr, u16 len,
const u8 *value, enum tpm_tis_io_mode mode);
+ int (*verify_crc)(struct tpm_tis_data *data, size_t len,
+ const u8 *value);
};

static inline int tpm_tis_read_bytes(struct tpm_tis_data *data, u32 addr,
@@ -188,6 +190,14 @@ static inline int tpm_tis_write32(struct tpm_tis_data *data, u32 addr,
return rc;
}

+static inline int tpm_tis_verify_crc(struct tpm_tis_data *data, size_t len,
+ const u8 *value)
+{
+ if (!data->phy_ops->verify_crc)
+ return 0;
+ return data->phy_ops->verify_crc(data, len, value);
+}
+
static inline bool is_bsw(void)
{
#ifdef CONFIG_X86
--
2.25.1
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