2 files changed, 25 insertions, 0 deletions

diff --git a/Documentation/devicetree/bindings/hwmon/jc42.txt b/Documentation/devicetree/bindings/hwmon/jc42.txt
index 07a250498fbb..f569db58f64a 100644
--- a/Documentation/devicetree/bindings/hwmon/jc42.txt
+++ b/Documentation/devicetree/bindings/hwmon/jc42.txt
@@ -34,6 +34,10 @@ Required properties:
 
 - reg: I2C address
 
+Optional properties:
+- smbus-timeout-disable: When set, the smbus timeout function will be disabled.
+                         This is not supported on all chips.
+
 Example:
 
 temp-sensor@1a {
diff --git a/drivers/hwmon/jc42.c b/drivers/hwmon/jc42.c
index 5f11dc014ed6..e5234f953a6d 100644
--- a/drivers/hwmon/jc42.c
+++ b/drivers/hwmon/jc42.c
@@ -22,6 +22,7 @@
  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  */
 
+#include <linux/bitops.h>
 #include <linux/module.h>
 #include <linux/init.h>
 #include <linux/slab.h>
@@ -45,6 +46,7 @@ static const unsigned short normal_i2c[] = {
 #define JC42_REG_TEMP           0x05
 #define JC42_REG_MANID          0x06
 #define JC42_REG_DEVICEID       0x07
+#define JC42_REG_SMBUS          0x22 /* NXP and Atmel, possibly others? */
 
 /* Status bits in temperature register */
 #define JC42_ALARM_CRIT_BIT     15
@@ -75,6 +77,9 @@ static const unsigned short normal_i2c[] = {
 #define GT_MANID                0x1c68  /* Giantec */
 #define GT_MANID2               0x132d  /* Giantec, 2nd mfg ID */
 
+/* SMBUS register */
+#define SMBUS_STMOUT            BIT(7)  /* SMBus time-out, active low */
+
 /* Supported chips */
 
 /* Analog Devices */
@@ -495,6 +500,22 @@ static int jc42_probe(struct i2c_client *client, const struct i2c_device_id *id)
 
         data->extended = !!(cap & JC42_CAP_RANGE);
 
+        if (device_property_read_bool(dev, "smbus-timeout-disable")) {
+                int smbus;
+
+                /*
+                 * Not all chips support this register, but from a
+                 * quick read of various datasheets no chip appears
+                 * incompatible with the below attempt to disable
+                 * the timeout. And the whole thing is opt-in...
+                 */
+                smbus = i2c_smbus_read_word_swapped(client, JC42_REG_SMBUS);
+                if (smbus < 0)
+                        return smbus;
+                i2c_smbus_write_word_swapped(client, JC42_REG_SMBUS,
+                                             smbus | SMBUS_STMOUT);
+        }
+
         config = i2c_smbus_read_word_swapped(client, JC42_REG_CONFIG);
         if (config < 0)
                 return config;