tpm: Apply a sane minimum adapterlimit value for retransmission.

When the I2C Infineon part is attached to an I2C adapter that imposes
a size limitation, large requests will fail with -EOPNOTSUPP. Retry
them with a sane minimum size without re-issuing the 0x05 command
as this appears to occasionally put the TPM in a bad state.

Signed-off-by: Bryan Freed <bfreed@chromium.org>
[rework the patch to adapt to the feedback received]
Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Acked-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>

diff --git a/drivers/char/tpm/tpm_i2c_infineon.c b/drivers/char/tpm/tpm_i2c_infineon.c
index dc47fa2..79d6bbb 100644 (file)
--- a/drivers/char/tpm/tpm_i2c_infineon.c
+++ b/drivers/char/tpm/tpm_i2c_infineon.c
@@ -70,6 +70,7 @@ struct tpm_inf_dev {
        u8 buf[TPM_BUFSIZE + sizeof(u8)]; /* max. buffer size + addr */
        struct tpm_chip *chip;
        enum i2c_chip_type chip_type;
+       unsigned int adapterlimit;
 };
 
 static struct tpm_inf_dev tpm_dev;
@@ -111,6 +112,7 @@ static int iic_tpm_read(u8 addr, u8 *buffer, size_t len)
 
        int rc = 0;
        int count;
+       unsigned int msglen = len;
 
        /* Lock the adapter for the duration of the whole sequence. */
        if (!tpm_dev.client->adapter->algo->master_xfer)
@@ -131,27 +133,61 @@ static int iic_tpm_read(u8 addr, u8 *buffer, size_t len)
                        usleep_range(SLEEP_DURATION_LOW, SLEEP_DURATION_HI);
                }
        } else {
-               /* slb9635 protocol should work in all cases */
-               for (count = 0; count < MAX_COUNT; count++) {
-                       rc = __i2c_transfer(tpm_dev.client->adapter, &msg1, 1);
-                       if (rc > 0)
-                               break;  /* break here to skip sleep */
-
-                       usleep_range(SLEEP_DURATION_LOW, SLEEP_DURATION_HI);
-               }
-
-               if (rc <= 0)
-                       goto out;
-
-               /* After the TPM has successfully received the register address
-                * it needs some time, thus we're sleeping here again, before
-                * retrieving the data
+               /* Expect to send one command message and one data message, but
+                * support looping over each or both if necessary.
                 */
-               for (count = 0; count < MAX_COUNT; count++) {
-                       usleep_range(SLEEP_DURATION_LOW, SLEEP_DURATION_HI);
-                       rc = __i2c_transfer(tpm_dev.client->adapter, &msg2, 1);
-                       if (rc > 0)
-                               break;
+               while (len > 0) {
+                       /* slb9635 protocol should work in all cases */
+                       for (count = 0; count < MAX_COUNT; count++) {
+                               rc = __i2c_transfer(tpm_dev.client->adapter,
+                                                   &msg1, 1);
+                               if (rc > 0)
+                                       break;  /* break here to skip sleep */
+
+                               usleep_range(SLEEP_DURATION_LOW,
+                                            SLEEP_DURATION_HI);
+                       }
+
+                       if (rc <= 0)
+                               goto out;
+
+                       /* After the TPM has successfully received the register
+                        * address it needs some time, thus we're sleeping here
+                        * again, before retrieving the data
+                        */
+                       for (count = 0; count < MAX_COUNT; count++) {
+                               if (tpm_dev.adapterlimit) {
+                                       msglen = min_t(unsigned int,
+                                                      tpm_dev.adapterlimit,
+                                                      len);
+                                       msg2.len = msglen;
+                               }
+                               usleep_range(SLEEP_DURATION_LOW,
+                                            SLEEP_DURATION_HI);
+                               rc = __i2c_transfer(tpm_dev.client->adapter,
+                                                   &msg2, 1);
+                               if (rc > 0) {
+                                       /* Since len is unsigned, make doubly
+                                        * sure we do not underflow it.
+                                        */
+                                       if (msglen > len)
+                                               len = 0;
+                                       else
+                                               len -= msglen;
+                                       msg2.buf += msglen;
+                                       break;
+                               }
+                               /* If the I2C adapter rejected the request (e.g
+                                * when the quirk read_max_len < len) fall back
+                                * to a sane minimum value and try again.
+                                */
+                               if (rc == -EOPNOTSUPP)
+                                       tpm_dev.adapterlimit =
+                                                       I2C_SMBUS_BLOCK_MAX;
+                       }
+
+                       if (rc <= 0)
+                               goto out;
                }
        }