[PATCH 3/3] char: tpm: cr50: Move i2c locking to request/relinquish locality ops

[Jan Dabros <jsd@semihalf.com>]

Move i2c locking primitives to request_locality and relinquish_locality
callbacks, what effectively blocks TPM bus for the whole duration of
logical TPM operation.

With this in place, cr50-equipped TPM may be shared with external CPUs -
assuming that underneath i2c controller driver is aware of this setup
(see i2c-designware-amdpsp as an example).

Signed-off-by: Jan Dabros <jsd@semihalf.com>
---
 drivers/char/tpm/tpm_tis_i2c_cr50.c | 22 +++++++++++++---------
 1 file changed, 13 insertions(+), 9 deletions(-)

diff --git a/drivers/char/tpm/tpm_tis_i2c_cr50.c b/drivers/char/tpm/tpm_tis_i2c_cr50.c
index d3438a4ed1ef8..c6628351ec383 100644
--- a/drivers/char/tpm/tpm_tis_i2c_cr50.c
+++ b/drivers/char/tpm/tpm_tis_i2c_cr50.c
@@ -202,8 +202,6 @@ static int tpm_cr50_i2c_read(struct tpm_chip *chip, u8 addr, u8 *buffer, size_t
 	};
 	int rc;
 
-	i2c_lock_bus(client->adapter, I2C_LOCK_SEGMENT);
-
 	/* Prepare for completion interrupt */
 	tpm_cr50_i2c_enable_tpm_irq(chip);
 
@@ -222,7 +220,6 @@ static int tpm_cr50_i2c_read(struct tpm_chip *chip, u8 addr, u8 *buffer, size_t
 
 out:
 	tpm_cr50_i2c_disable_tpm_irq(chip);
-	i2c_unlock_bus(client->adapter, I2C_LOCK_SEGMENT);
 
 	if (rc < 0)
 		return rc;
@@ -264,8 +261,6 @@ static int tpm_cr50_i2c_write(struct tpm_chip *chip, u8 addr, u8 *buffer,
 	priv->buf[0] = addr;
 	memcpy(priv->buf + 1, buffer, len);
 
-	i2c_lock_bus(client->adapter, I2C_LOCK_SEGMENT);
-
 	/* Prepare for completion interrupt */
 	tpm_cr50_i2c_enable_tpm_irq(chip);
 
@@ -279,7 +274,6 @@ static int tpm_cr50_i2c_write(struct tpm_chip *chip, u8 addr, u8 *buffer,
 
 out:
 	tpm_cr50_i2c_disable_tpm_irq(chip);
-	i2c_unlock_bus(client->adapter, I2C_LOCK_SEGMENT);
 
 	if (rc < 0)
 		return rc;
@@ -323,6 +317,7 @@ static int tpm_cr50_check_locality(struct tpm_chip *chip, int loc)
  */
 static int tpm_cr50_release_locality(struct tpm_chip *chip, int loc)
 {
+	struct i2c_client *client = to_i2c_client(chip->dev.parent);
 	u8 mask = TPM_ACCESS_VALID | TPM_ACCESS_REQUEST_PENDING;
 	u8 addr = TPM_I2C_ACCESS(loc);
 	u8 buf;
@@ -330,13 +325,15 @@ static int tpm_cr50_release_locality(struct tpm_chip *chip, int loc)
 
 	rc = tpm_cr50_i2c_read(chip, addr, &buf, sizeof(buf));
 	if (rc < 0)
-		return rc;
+		goto unlock_out;
 
 	if ((buf & mask) == mask) {
 		buf = TPM_ACCESS_ACTIVE_LOCALITY;
 		rc = tpm_cr50_i2c_write(chip, addr, &buf, sizeof(buf));
 	}
 
+unlock_out:
+	i2c_unlock_bus(client->adapter, I2C_LOCK_SEGMENT);
 	return rc;
 }
 
@@ -351,16 +348,19 @@ static int tpm_cr50_release_locality(struct tpm_chip *chip, int loc)
  */
 static int tpm_cr50_request_locality(struct tpm_chip *chip, int loc)
 {
+	struct i2c_client *client = to_i2c_client(chip->dev.parent);
 	u8 buf = TPM_ACCESS_REQUEST_USE;
 	unsigned long stop;
 	int rc;
 
+	i2c_lock_bus(client->adapter, I2C_LOCK_SEGMENT);
+
 	if (tpm_cr50_check_locality(chip, loc) == loc)
 		return loc;
 
 	rc = tpm_cr50_i2c_write(chip, TPM_I2C_ACCESS(loc), &buf, sizeof(buf));
 	if (rc < 0)
-		return rc;
+		goto unlock_out;
 
 	stop = jiffies + chip->timeout_a;
 	do {
@@ -370,7 +370,11 @@ static int tpm_cr50_request_locality(struct tpm_chip *chip, int loc)
 		msleep(TPM_CR50_TIMEOUT_SHORT_MS);
 	} while (time_before(jiffies, stop));
 
-	return -ETIMEDOUT;
+	rc = -ETIMEDOUT;
+
+unlock_out:
+	i2c_unlock_bus(client->adapter, I2C_LOCK_SEGMENT);
+	return rc;
 }
 
 /**
-- 
2.38.1.273.g43a17bfeac-goog