[v6,2/7] tpm: tpm_tis: Add check_data handle to tpm_tis_phy_ops
diff mbox series

Message ID 20200407162044.168890-3-amirmizi6@gmail.com
State New
Headers show
Series
  • Add tpm i2c ptp driver
Related show

Commit Message

Amir Mizinski April 7, 2020, 4:20 p.m. UTC
From: Amir Mizinski <amirmizi6@gmail.com>

In order to validate data integrity we need to compute the crc over the data
sent in lower layer (I2C for instance).
To do that tpm_tis_check_data() calls a "check_data" operation (if available).
If data integrity check fails, a retry to save the sent/received
data is implemented in tpm_tis_send_main()/tpm_tis_recv() functions.

Considering this commit, the following steps are done when sending a command:
   1. Host writes to TPM_STS.commandReady.
   2. Host writes command.
   3. Host checks that TPM received data is valid.
   4. If data is currupted go to step 1.

When receiving data:
   1. Host checks that TPM_STS.dataAvail is set.
   2. Host saves received data.
   3. Host checks that received data is correct.
   4. If data is currupted Host writes to TPM_STS.responseRetry and go to
      step 1.

Co-developed-by: Christophe Ricard <christophe-h.ricard@st.com>
Signed-off-by: Christophe Ricard <christophe-h.ricard@st.com>
Signed-off-by: Amir Mizinski <amirmizi6@gmail.com>
---
 drivers/char/tpm/tpm_tis_core.c | 102 +++++++++++++++++++++++++---------------
 drivers/char/tpm/tpm_tis_core.h |   3 ++
 2 files changed, 67 insertions(+), 38 deletions(-)

Comments

Jarkko Sakkinen April 8, 2020, 6:33 p.m. UTC | #1
On Tue, Apr 07, 2020 at 07:20:39PM +0300, amirmizi6@gmail.com wrote:
> From: Amir Mizinski <amirmizi6@gmail.com>
> 
> In order to validate data integrity we need to compute the crc over the data
> sent in lower layer (I2C for instance).

s/crc/CRC/

> To do that tpm_tis_check_data() calls a "check_data" operation (if available).

"check_data" does not exist.

> If data integrity check fails, a retry to save the sent/received
> data is implemented in tpm_tis_send_main()/tpm_tis_recv() functions.
> 
> Considering this commit, the following steps are done when sending a command:
>    1. Host writes to TPM_STS.commandReady.
>    2. Host writes command.
>    3. Host checks that TPM received data is valid.
>    4. If data is currupted go to step 1.
> 
> When receiving data:
>    1. Host checks that TPM_STS.dataAvail is set.
>    2. Host saves received data.
>    3. Host checks that received data is correct.
>    4. If data is currupted Host writes to TPM_STS.responseRetry and go to
>       step 1.

These sequences in the commit message look somewhat uselss. Maybe
just remove them.

> 
> Co-developed-by: Christophe Ricard <christophe-h.ricard@st.com>
> Signed-off-by: Christophe Ricard <christophe-h.ricard@st.com>
> Signed-off-by: Amir Mizinski <amirmizi6@gmail.com>
> ---
>  drivers/char/tpm/tpm_tis_core.c | 102 +++++++++++++++++++++++++---------------
>  drivers/char/tpm/tpm_tis_core.h |   3 ++
>  2 files changed, 67 insertions(+), 38 deletions(-)
> 
> diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
> index 27c6ca0..6c4f232 100644
> --- a/drivers/char/tpm/tpm_tis_core.c
> +++ b/drivers/char/tpm/tpm_tis_core.c
> @@ -242,6 +242,15 @@ static u8 tpm_tis_status(struct tpm_chip *chip)
>  	return status;
>  }
>  
> +static bool tpm_tis_check_data(struct tpm_chip *chip, const u8 *buf, size_t len)

Not sure if this is the best possible function name, "check" can
mean almost anything.

> +{
> +	struct tpm_tis_data *priv = dev_get_drvdata(&chip->dev);
> +
> +	if (priv->phy_ops->check_data)
> +		return priv->phy_ops->check_data(priv, buf, len);

New line here before the return statement.

> +	return true;
> +}
> +
>  static void tpm_tis_ready(struct tpm_chip *chip)
>  {
>  	struct tpm_tis_data *priv = dev_get_drvdata(&chip->dev);
> @@ -308,47 +317,59 @@ static int tpm_tis_recv(struct tpm_chip *chip, u8 *buf, size_t count)
>  {
>  	struct tpm_tis_data *priv = dev_get_drvdata(&chip->dev);
>  	int size = 0;
> -	int status;
> +	int status, i;
>  	u32 expected;
> +	bool check_data = false;
>  
> -	if (count < TPM_HEADER_SIZE) {
> -		size = -EIO;
> -		goto out;
> -	}
> +	for (i = 0; i < TPM_RETRY; i++) {
> +		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) {
> -		dev_err(&chip->dev, "Unable to read header\n");
> -		goto out;
> -	}
> +		size = recv_data(chip, buf, TPM_HEADER_SIZE);
> +		/* read first 10 bytes, including tag, paramsize, and result */
> +		if (size < TPM_HEADER_SIZE) {
> +			dev_err(&chip->dev, "Unable to read header\n");
> +			goto out;
> +		}
>  
> -	expected = be32_to_cpu(*(__be32 *) (buf + 2));
> -	if (expected > count || expected < TPM_HEADER_SIZE) {
> -		size = -EIO;
> -		goto out;
> -	}
> +		expected = be32_to_cpu(*(__be32 *) (buf + 2));
> +		if (expected > count || expected < TPM_HEADER_SIZE) {
> +			size = -EIO;
> +			goto out;
> +		}
>  
> -	size += recv_data(chip, &buf[TPM_HEADER_SIZE],
> -			  expected - TPM_HEADER_SIZE);
> -	if (size < expected) {
> -		dev_err(&chip->dev, "Unable to read remainder of result\n");
> -		size = -ETIME;
> -		goto out;
> -	}
> +		size += recv_data(chip, &buf[TPM_HEADER_SIZE],
> +				  expected - TPM_HEADER_SIZE);
> +		if (size < expected) {
> +			dev_err(&chip->dev, "Unable to read remainder of result\n");
> +			size = -ETIME;
> +			goto out;
> +		}
>  
> -	if (wait_for_tpm_stat(chip, TPM_STS_VALID, chip->timeout_c,
> -				&priv->int_queue, false) < 0) {
> -		size = -ETIME;
> -		goto out;
> +		if (wait_for_tpm_stat(chip, TPM_STS_VALID, chip->timeout_c,
> +				      &priv->int_queue, false) < 0) {
> +			size = -ETIME;
> +			goto out;
> +		}
> +
> +		status = tpm_tis_status(chip);
> +		if (status & TPM_STS_DATA_AVAIL) {	/* retry? */
> +			dev_err(&chip->dev, "Error left over data\n");
> +			size = -EIO;
> +			goto out;
> +		}
> +
> +		check_data = tpm_tis_check_data(chip, buf, size);
> +		if (!check_data)
> +			tpm_tis_write8(priv, TPM_STS(priv->locality),
> +				       TPM_STS_RESPONSE_RETRY);
> +		else
> +			break;
>  	}
> -	status = tpm_tis_status(chip);
> -	if (status & TPM_STS_DATA_AVAIL) {	/* retry? */
> -		dev_err(&chip->dev, "Error left over data\n");
> +	if (!check_data)
>  		size = -EIO;
> -		goto out;
> -	}
> -
>  out:
>  	tpm_tis_ready(chip);
>  	return size;
> @@ -453,14 +474,19 @@ static void disable_interrupts(struct tpm_chip *chip)
>  static int tpm_tis_send_main(struct tpm_chip *chip, const u8 *buf, size_t len)
>  {
>  	struct tpm_tis_data *priv = dev_get_drvdata(&chip->dev);
> -	int rc;
> +	int rc, i;
>  	u32 ordinal;
>  	unsigned long dur;
> +	bool data_valid = false;
>  
> -	rc = tpm_tis_send_data(chip, buf, len);
> -	if (rc < 0)
> -		return rc;
> -
> +	for (i = 0; i < TPM_RETRY && !data_valid; i++) {
> +		rc = tpm_tis_send_data(chip, buf, len);
> +		if (rc < 0)
> +			return rc;
> +		data_valid = tpm_tis_check_data(chip, buf, len);
> +	}
> +	if (!data_valid)
> +		return -EIO;
>  	/* 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 d06c65b..486c2e9 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,
>  };
>  
>  enum tis_int_flags {
> @@ -106,6 +107,8 @@ struct tpm_tis_phy_ops {
>  	int (*read16)(struct tpm_tis_data *data, u32 addr, u16 *result);
>  	int (*read32)(struct tpm_tis_data *data, u32 addr, u32 *result);
>  	int (*write32)(struct tpm_tis_data *data, u32 addr, u32 src);
> +	bool (*check_data)(struct tpm_tis_data *data, const u8 *buf,
> +			   size_t len);

Aren't you validating the contents of the buf?

/Jarkko
Jarkko Sakkinen April 12, 2020, 1:53 p.m. UTC | #2
There is something seriously wrong in your email client.
Please reconfigure your email client according to:

https://www.kernel.org/doc/html/v5.5/process/email-clients.html

Then re-response.

This is.. I've lost to the count how many times I've requsted this.

Thanks.

/Jarkko
Amir Mizinski April 21, 2020, 1:34 p.m. UTC | #3
Hello jarkko,
I reconfigure my email client by the instructions you've sent, and
re-responsing as you requested.
please tell me if there are still any issues. thank you.

On 2020-04-08 18:33, Jarkko Sakkinen wrote:
> On Tue, Apr 07, 2020 at 07:20:39PM +0300, amirmizi6@gmail.com wrote:
>> From: Amir Mizinski <amirmizi6@gmail.com>
>>
>> In order to validate data integrity we need to compute the crc over the data
>> sent in lower layer (I2C for instance).
>
> s/crc/CRC/
>
>> To do that tpm_tis_check_data() calls a "check_data" operation (if available).
>
> "check_data" does not exist.
>

it is added in this commit to "tpm_tis_phy_ops" struct in
"tpm_tis_core.h", which is inherited in "tpm_tis_i2c.c" on later patch
(7/7).

>> If data integrity check fails, a retry to save the sent/received
>> data is implemented in tpm_tis_send_main()/tpm_tis_recv() functions.
>>
>> Considering this commit, the following steps are done when sending a command:
>>    1. Host writes to TPM_STS.commandReady.
>>    2. Host writes command.
>>    3. Host checks that TPM received data is valid.
>>    4. If data is currupted go to step 1.
>>
>> When receiving data:
>>    1. Host checks that TPM_STS.dataAvail is set.
>>    2. Host saves received data.
>>    3. Host checks that received data is correct.
>>    4. If data is currupted Host writes to TPM_STS.responseRetry and go to
>>       step 1.
>
> These sequences in the commit message look somewhat uselss. Maybe
> just remove them.
>

Their main porpose is to describe how the retry attempt is implemented
in case of currupted data.
should i just describe that with a few words or that's unnecessary?

>>
>> Co-developed-by: Christophe Ricard <christophe-h.ricard@st.com>
>> Signed-off-by: Christophe Ricard <christophe-h.ricard@st.com>
>> Signed-off-by: Amir Mizinski <amirmizi6@gmail.com>
>> ---
>>  drivers/char/tpm/tpm_tis_core.c | 102 +++++++++++++++++++++++++---------------
>>  drivers/char/tpm/tpm_tis_core.h |   3 ++
>>  2 files changed, 67 insertions(+), 38 deletions(-)
>>
>> diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
>> index 27c6ca0..6c4f232 100644
>> --- a/drivers/char/tpm/tpm_tis_core.c
>> +++ b/drivers/char/tpm/tpm_tis_core.c
>> @@ -242,6 +242,15 @@ static u8 tpm_tis_status(struct tpm_chip *chip)
>>      return status;
>>  }
>>  
>> +static bool tpm_tis_check_data(struct tpm_chip *chip, const u8 *buf, size_t len)
>
> Not sure if this is the best possible function name, "check" can
> mean almost anything.
>

Ok, i'm changing it to "verify_data_integrity". is that ok?

>> +{
>> +    struct tpm_tis_data *priv = dev_get_drvdata(&chip->dev);
>> +
>> +    if (priv->phy_ops->check_data)
>> +        return priv->phy_ops->check_data(priv, buf, len);
>
> New line here before the return statement.
>
>> +    return true;
>> +}
>> +
>>  static void tpm_tis_ready(struct tpm_chip *chip)
>>  {
>>      struct tpm_tis_data *priv = dev_get_drvdata(&chip->dev);
>> @@ -308,47 +317,59 @@ static int tpm_tis_recv(struct tpm_chip *chip, u8 *buf, size_t count)
>>  {
>>      struct tpm_tis_data *priv = dev_get_drvdata(&chip->dev);
>>      int size = 0;
>> -    int status;
>> +    int status, i;
>>      u32 expected;
>> +    bool check_data = false;
>>  
>> -    if (count < TPM_HEADER_SIZE) {
>> -        size = -EIO;
>> -        goto out;
>> -    }
>> +    for (i = 0; i < TPM_RETRY; i++) {
>> +        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) {
>> -        dev_err(&chip->dev, "Unable to read header\n");
>> -        goto out;
>> -    }
>> +        size = recv_data(chip, buf, TPM_HEADER_SIZE);
>> +        /* read first 10 bytes, including tag, paramsize, and result */
>> +        if (size < TPM_HEADER_SIZE) {
>> +            dev_err(&chip->dev, "Unable to read header\n");
>> +            goto out;
>> +        }
>>  
>> -    expected = be32_to_cpu(*(__be32 *) (buf + 2));
>> -    if (expected > count || expected < TPM_HEADER_SIZE) {
>> -        size = -EIO;
>> -        goto out;
>> -    }
>> +        expected = be32_to_cpu(*(__be32 *) (buf + 2));
>> +        if (expected > count || expected < TPM_HEADER_SIZE) {
>> +            size = -EIO;
>> +            goto out;
>> +        }
>>  
>> -    size += recv_data(chip, &buf[TPM_HEADER_SIZE],
>> -              expected - TPM_HEADER_SIZE);
>> -    if (size < expected) {
>> -        dev_err(&chip->dev, "Unable to read remainder of result\n");
>> -        size = -ETIME;
>> -        goto out;
>> -    }
>> +        size += recv_data(chip, &buf[TPM_HEADER_SIZE],
>> +                  expected - TPM_HEADER_SIZE);
>> +        if (size < expected) {
>> +            dev_err(&chip->dev, "Unable to read remainder of result\n");
>> +            size = -ETIME;
>> +            goto out;
>> +        }
>>  
>> -    if (wait_for_tpm_stat(chip, TPM_STS_VALID, chip->timeout_c,
>> -                &priv->int_queue, false) < 0) {
>> -        size = -ETIME;
>> -        goto out;
>> +        if (wait_for_tpm_stat(chip, TPM_STS_VALID, chip->timeout_c,
>> +                      &priv->int_queue, false) < 0) {
>> +            size = -ETIME;
>> +            goto out;
>> +        }
>> +
>> +        status = tpm_tis_status(chip);
>> +        if (status & TPM_STS_DATA_AVAIL) {    /* retry? */
>> +            dev_err(&chip->dev, "Error left over data\n");
>> +            size = -EIO;
>> +            goto out;
>> +        }
>> +
>> +        check_data = tpm_tis_check_data(chip, buf, size);
>> +        if (!check_data)
>> +            tpm_tis_write8(priv, TPM_STS(priv->locality),
>> +                       TPM_STS_RESPONSE_RETRY);
>> +        else
>> +            break;
>>      }
>> -    status = tpm_tis_status(chip);
>> -    if (status & TPM_STS_DATA_AVAIL) {    /* retry? */
>> -        dev_err(&chip->dev, "Error left over data\n");
>> +    if (!check_data)
>>          size = -EIO;
>> -        goto out;
>> -    }
>> -
>>  out:
>>      tpm_tis_ready(chip);
>>      return size;
>> @@ -453,14 +474,19 @@ static void disable_interrupts(struct tpm_chip *chip)
>>  static int tpm_tis_send_main(struct tpm_chip *chip, const u8 *buf, size_t len)
>>  {
>>      struct tpm_tis_data *priv = dev_get_drvdata(&chip->dev);
>> -    int rc;
>> +    int rc, i;
>>      u32 ordinal;
>>      unsigned long dur;
>> +    bool data_valid = false;
>>  
>> -    rc = tpm_tis_send_data(chip, buf, len);
>> -    if (rc < 0)
>> -        return rc;
>> -
>> +    for (i = 0; i < TPM_RETRY && !data_valid; i++) {
>> +        rc = tpm_tis_send_data(chip, buf, len);
>> +        if (rc < 0)
>> +            return rc;
>> +        data_valid = tpm_tis_check_data(chip, buf, len);
>> +    }
>> +    if (!data_valid)
>> +        return -EIO;
>>      /* 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 d06c65b..486c2e9 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,
>>  };
>>  
>>  enum tis_int_flags {
>> @@ -106,6 +107,8 @@ struct tpm_tis_phy_ops {
>>      int (*read16)(struct tpm_tis_data *data, u32 addr, u16 *result);
>>      int (*read32)(struct tpm_tis_data *data, u32 addr, u32 *result);
>>      int (*write32)(struct tpm_tis_data *data, u32 addr, u32 src);
>> +    bool (*check_data)(struct tpm_tis_data *data, const u8 *buf,
>> +               size_t len);
>
> Aren't you validating the contents of the buf?
>
> /Jarkko

i do.
when sending, the data is written to the buff in "tpm_tis_send_data(chip,buf, len)".
and validated in "data_valid = tpm_tis_check_data(chip, buf, len)".
data is not sent until TPM_STS_GO is set.

when receiving, the data in the buffer is verified after recv_data, and
writing to TPM_STS_RESPONSE_RETRY in case it fails to recive it again.


Thank you
Amir Mizinski
Jarkko Sakkinen April 21, 2020, 8:19 p.m. UTC | #4
On Tue, Apr 21, 2020 at 01:34:44PM +0000, Amir Mizinski wrote:
> 
> Hello jarkko,
> I reconfigure my email client by the instructions you've sent, and
> re-responsing as you requested.
> please tell me if there are still any issues. thank you.

This is great, thanks a lot!

Easy enough to check too:

https://lore.kernel.org/linux-integrity/0cfa0486-8ccb-d7d1-acf2-ca103f723b3a@gmail.com/

It wouldn't end up to the ML if your config wasn't correct.

/Jarkko

Patch
diff mbox series

diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
index 27c6ca0..6c4f232 100644
--- a/drivers/char/tpm/tpm_tis_core.c
+++ b/drivers/char/tpm/tpm_tis_core.c
@@ -242,6 +242,15 @@  static u8 tpm_tis_status(struct tpm_chip *chip)
 	return status;
 }
 
+static bool tpm_tis_check_data(struct tpm_chip *chip, const u8 *buf, size_t len)
+{
+	struct tpm_tis_data *priv = dev_get_drvdata(&chip->dev);
+
+	if (priv->phy_ops->check_data)
+		return priv->phy_ops->check_data(priv, buf, len);
+	return true;
+}
+
 static void tpm_tis_ready(struct tpm_chip *chip)
 {
 	struct tpm_tis_data *priv = dev_get_drvdata(&chip->dev);
@@ -308,47 +317,59 @@  static int tpm_tis_recv(struct tpm_chip *chip, u8 *buf, size_t count)
 {
 	struct tpm_tis_data *priv = dev_get_drvdata(&chip->dev);
 	int size = 0;
-	int status;
+	int status, i;
 	u32 expected;
+	bool check_data = false;
 
-	if (count < TPM_HEADER_SIZE) {
-		size = -EIO;
-		goto out;
-	}
+	for (i = 0; i < TPM_RETRY; i++) {
+		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) {
-		dev_err(&chip->dev, "Unable to read header\n");
-		goto out;
-	}
+		size = recv_data(chip, buf, TPM_HEADER_SIZE);
+		/* read first 10 bytes, including tag, paramsize, and result */
+		if (size < TPM_HEADER_SIZE) {
+			dev_err(&chip->dev, "Unable to read header\n");
+			goto out;
+		}
 
-	expected = be32_to_cpu(*(__be32 *) (buf + 2));
-	if (expected > count || expected < TPM_HEADER_SIZE) {
-		size = -EIO;
-		goto out;
-	}
+		expected = be32_to_cpu(*(__be32 *) (buf + 2));
+		if (expected > count || expected < TPM_HEADER_SIZE) {
+			size = -EIO;
+			goto out;
+		}
 
-	size += recv_data(chip, &buf[TPM_HEADER_SIZE],
-			  expected - TPM_HEADER_SIZE);
-	if (size < expected) {
-		dev_err(&chip->dev, "Unable to read remainder of result\n");
-		size = -ETIME;
-		goto out;
-	}
+		size += recv_data(chip, &buf[TPM_HEADER_SIZE],
+				  expected - TPM_HEADER_SIZE);
+		if (size < expected) {
+			dev_err(&chip->dev, "Unable to read remainder of result\n");
+			size = -ETIME;
+			goto out;
+		}
 
-	if (wait_for_tpm_stat(chip, TPM_STS_VALID, chip->timeout_c,
-				&priv->int_queue, false) < 0) {
-		size = -ETIME;
-		goto out;
+		if (wait_for_tpm_stat(chip, TPM_STS_VALID, chip->timeout_c,
+				      &priv->int_queue, false) < 0) {
+			size = -ETIME;
+			goto out;
+		}
+
+		status = tpm_tis_status(chip);
+		if (status & TPM_STS_DATA_AVAIL) {	/* retry? */
+			dev_err(&chip->dev, "Error left over data\n");
+			size = -EIO;
+			goto out;
+		}
+
+		check_data = tpm_tis_check_data(chip, buf, size);
+		if (!check_data)
+			tpm_tis_write8(priv, TPM_STS(priv->locality),
+				       TPM_STS_RESPONSE_RETRY);
+		else
+			break;
 	}
-	status = tpm_tis_status(chip);
-	if (status & TPM_STS_DATA_AVAIL) {	/* retry? */
-		dev_err(&chip->dev, "Error left over data\n");
+	if (!check_data)
 		size = -EIO;
-		goto out;
-	}
-
 out:
 	tpm_tis_ready(chip);
 	return size;
@@ -453,14 +474,19 @@  static void disable_interrupts(struct tpm_chip *chip)
 static int tpm_tis_send_main(struct tpm_chip *chip, const u8 *buf, size_t len)
 {
 	struct tpm_tis_data *priv = dev_get_drvdata(&chip->dev);
-	int rc;
+	int rc, i;
 	u32 ordinal;
 	unsigned long dur;
+	bool data_valid = false;
 
-	rc = tpm_tis_send_data(chip, buf, len);
-	if (rc < 0)
-		return rc;
-
+	for (i = 0; i < TPM_RETRY && !data_valid; i++) {
+		rc = tpm_tis_send_data(chip, buf, len);
+		if (rc < 0)
+			return rc;
+		data_valid = tpm_tis_check_data(chip, buf, len);
+	}
+	if (!data_valid)
+		return -EIO;
 	/* 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 d06c65b..486c2e9 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,
 };
 
 enum tis_int_flags {
@@ -106,6 +107,8 @@  struct tpm_tis_phy_ops {
 	int (*read16)(struct tpm_tis_data *data, u32 addr, u16 *result);
 	int (*read32)(struct tpm_tis_data *data, u32 addr, u32 *result);
 	int (*write32)(struct tpm_tis_data *data, u32 addr, u32 src);
+	bool (*check_data)(struct tpm_tis_data *data, const u8 *buf,
+			   size_t len);
 };
 
 static inline int tpm_tis_read_bytes(struct tpm_tis_data *data, u32 addr,