tpm: tis_i2c: Limit read bursts to I2C_SMBUS_BLOCK_MAX (32) bytes

Underlying I2C bus drivers not always support longer transfers and
imx-lpi2c for instance doesn't. SLB 9673 offers 427-bytes packets.

Visible symptoms are:

tpm tpm0: Error left over data
tpm tpm0: tpm_transmit: tpm_recv: error -5
tpm_tis_i2c: probe of 1-002e failed with error -5

Cc: stable@vger.kernel.org # v5.20+
Fixes: bbc23a07b072 ("tpm: Add tpm_tis_i2c backend for tpm_tis_core")
Tested-by: Michael Haener <michael.haener@siemens.com>
Signed-off-by: Alexander Sverdlin <alexander.sverdlin@siemens.com>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Reviewed-by: Jerry Snitselaar <jsnitsel@redhat.com>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>

diff --git a/drivers/char/tpm/tpm_tis_i2c.c b/drivers/char/tpm/tpm_tis_i2c.c
index c8c34ad..106fd20 100644 (file)
--- a/drivers/char/tpm/tpm_tis_i2c.c
+++ b/drivers/char/tpm/tpm_tis_i2c.c
@@ -189,21 +189,28 @@ static int tpm_tis_i2c_read_bytes(struct tpm_tis_data *data, u32 addr, u16 len,
        int ret;
 
        for (i = 0; i < TPM_RETRY; i++) {
-               /* write register */
-               msg.len = sizeof(reg);
-               msg.buf = &reg;
-               msg.flags = 0;
-               ret = tpm_tis_i2c_retry_transfer_until_ack(data, &msg);
-               if (ret < 0)
-                       return ret;
-
-               /* read data */
-               msg.buf = result;
-               msg.len = len;
-               msg.flags = I2C_M_RD;
-               ret = tpm_tis_i2c_retry_transfer_until_ack(data, &msg);
-               if (ret < 0)
-                       return ret;
+               u16 read = 0;
+
+               while (read < len) {
+                       /* write register */
+                       msg.len = sizeof(reg);
+                       msg.buf = &reg;
+                       msg.flags = 0;
+                       ret = tpm_tis_i2c_retry_transfer_until_ack(data, &msg);
+                       if (ret < 0)
+                               return ret;
+
+                       /* read data */
+                       msg.buf = result + read;
+                       msg.len = len - read;
+                       msg.flags = I2C_M_RD;
+                       if (msg.len > I2C_SMBUS_BLOCK_MAX)
+                               msg.len = I2C_SMBUS_BLOCK_MAX;
+                       ret = tpm_tis_i2c_retry_transfer_until_ack(data, &msg);
+                       if (ret < 0)
+                               return ret;
+                       read += msg.len;
+               }
 
                ret = tpm_tis_i2c_sanity_check_read(reg, len, result);
                if (ret == 0)