i2c: core: use I2C locking behaviour also for SMBUS

If I2C transfers are executed in atomic contexts, trylock is used
instead of lock. This behaviour was missing for SMBUS, although a lot of
transfers are of SMBUS type, either emulated or direct. So, factor out
the locking routine into a helper and use it for I2C and SMBUS.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
diff --git a/drivers/i2c/i2c-core.h b/drivers/i2c/i2c-core.h
index 9d85264..deea47c 100644
--- a/drivers/i2c/i2c-core.h
+++ b/drivers/i2c/i2c-core.h
@@ -39,6 +39,18 @@
 	return system_state > SYSTEM_RUNNING && irqs_disabled();
 }
 
+static inline int __i2c_lock_bus_helper(struct i2c_adapter *adap)
+{
+	int ret = 0;
+
+	if (i2c_in_atomic_xfer_mode())
+		ret = i2c_trylock_bus(adap, I2C_LOCK_SEGMENT) ? 0 : -EAGAIN;
+	else
+		i2c_lock_bus(adap, I2C_LOCK_SEGMENT);
+
+	return ret;
+}
+
 #ifdef CONFIG_ACPI
 const struct acpi_device_id *
 i2c_acpi_match_device(const struct acpi_device_id *matches,