[PATCH 2/2] tpm: tis_i2c: Limit write bursts to I2C_SMBUS_BLOCK_MAX (32) bytes

["A. Sverdlin" <alexander.sverdlin@siemens.com>]

From: Alexander Sverdlin <alexander.sverdlin@siemens.com>

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.

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>
---
 drivers/char/tpm/tpm_tis_i2c.c | 22 +++++++++++++++-------
 1 file changed, 15 insertions(+), 7 deletions(-)

diff --git a/drivers/char/tpm/tpm_tis_i2c.c b/drivers/char/tpm/tpm_tis_i2c.c
index 106fd20d94e4..82fda488e98b 100644
--- 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;
 }
-- 
2.40.1