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

Underlying I2C bus drivers not always support longer transfers and
imx-lpi2c for instance doesn't. The fix is symmetric to previous patch
which fixed the read direction.

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 106fd20..82fda48 100644 (file)
--- a/drivers/char/tpm/tpm_tis_i2c.c
+++ b/drivers/char/tpm/tpm_tis_i2c.c
@@ -230,19 +230,27 @@ static int tpm_tis_i2c_write_bytes(struct tpm_tis_data *data, u32 addr, u16 len,
        struct i2c_msg msg = { .addr = phy->i2c_client->addr };
        u8 reg = tpm_tis_i2c_address_to_register(addr);
        int ret;
+       u16 wrote = 0;
 
        if (len > TPM_BUFSIZE - 1)
                return -EIO;
 
-       /* write register and data in one go */
        phy->io_buf[0] = reg;
-       memcpy(phy->io_buf + sizeof(reg), value, len);
-
-       msg.len = sizeof(reg) + len;
        msg.buf = phy->io_buf;
-       ret = tpm_tis_i2c_retry_transfer_until_ack(data, &msg);
-       if (ret < 0)
-               return ret;
+       while (wrote < len) {
+               /* write register and data in one go */
+               msg.len = sizeof(reg) + len - wrote;
+               if (msg.len > I2C_SMBUS_BLOCK_MAX)
+                       msg.len = I2C_SMBUS_BLOCK_MAX;
+
+               memcpy(phy->io_buf + sizeof(reg), value + wrote,
+                      msg.len - sizeof(reg));
+
+               ret = tpm_tis_i2c_retry_transfer_until_ack(data, &msg);
+               if (ret < 0)
+                       return ret;
+               wrote += msg.len - sizeof(reg);
+       }
 
        return 0;
 }