[PATCH linux dev-5.8 2/3] pmbus: (ucd9000) Throttle SMBus transfers to avoid poor behaviour

[Andrew Jeffery]

Short turn-around times between transfers to UCD9000 devices can lead to
problematic behaviour, including unnecessary clock stretching, bus
lockups and potential corruption of the device's volatile state.

Introduce transfer throttling for the device with a minimum access
delay of 1ms.

Signed-off-by: Andrew Jeffery <andrew at aj.id.au>
---
 drivers/hwmon/pmbus/ucd9000.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/hwmon/pmbus/ucd9000.c b/drivers/hwmon/pmbus/ucd9000.c
index 81f4c4f166cd..7ba400d62475 100644
--- a/drivers/hwmon/pmbus/ucd9000.c
+++ b/drivers/hwmon/pmbus/ucd9000.c
@@ -487,6 +487,8 @@ static int ucd9000_init_debugfs(struct i2c_client *client,
 }
 #endif /* CONFIG_DEBUG_FS */
 
+#define UCD9000_SMBUS_THROTTLE_US	1000
+
 static int ucd9000_probe(struct i2c_client *client,
 			 const struct i2c_device_id *id)
 {
@@ -502,6 +504,8 @@ static int ucd9000_probe(struct i2c_client *client,
 				     I2C_FUNC_SMBUS_BLOCK_DATA))
 		return -ENODEV;
 
+	i2c_smbus_throttle_client(client, UCD9000_SMBUS_THROTTLE_US);
+
 	ret = i2c_smbus_read_block_data(client, UCD9000_DEVICE_ID,
 					block_buffer);
 	if (ret < 0) {
-- 
2.25.1