regulator: regmap helpers - support overlapping linear ranges

Don't give up voltage mapping if first range with suitable min/max uV does not provide the wanted voltage.

---

We may have HW which handles regulator voltage setting like:
LDO5 voltage reg:
bit [3] voltage range selection
bit [2:0] voltage selection where:

If D[3]=0,

000 = 0.7V
001 = 0.8V
010 = 0.9V
011 = 1.0V
100 = 1.1V
101 = 1.2V
110 = 1.3V
111 = 1.4V

If D[3]=1,

000 = 0.675V
001 = 0.775V
010 = 0.875V
011 = 0.975V
100 = 1.075V
101 = 1.175V
110 = 1.275V
111 = 1.375V

which can be described as:

REGULATOR_LINEAR_VOLTAGE(700000, 0x0, 0x7, 100000) REGULATOR_LINEAR_VOLTAGE(675000, 0x8, 0xF, 100000)

If consumer wants to use exactly 775000 uV current implementation of regulator_map_voltage_linear_range will pick up first range (as 775000 is between min uV and max uV for this range) and fail because first range is not supporting this voltage. This change makes regulator_map_voltage_linear_range to continue checking rest of the ranges if they support requested voltage before failing out.

Unfortunately this approach only works if 'range selection bit' follows immediately after voltage selection bits - which is not case for ROHM BD71837/BD71847 PMICs. Hence I will soon submit patch with helpers supporting 'pickable range' register - which would solve also this issue. Yet, the 'pickable range' solution is not as elegant as current linear range solution is (in my opinion) - hence I suggest this addition for cases where we have contagious vsel mask but overlapping linear ranges.

 drivers/regulator/helpers.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

index 2ae7c3ac5940..ef09021dc46e 100644
@@ -321,17 +321,18 @@ int regulator_map_voltage_linear_range(struct regulator_dev *rdev,
 
 		ret += range->min_sel;
 
-		break;
+		/*
+		 * Map back into a voltage to verify we're still in bounds.
+		 * If we are not, then continue checking rest of the ranges.
+		 */
+		voltage = rdev->desc->ops->list_voltage(rdev, ret);
+		if (voltage >= min_uV && voltage <= max_uV)
+			break;
 	}
 
 	if (i == rdev->desc->n_linear_ranges)
 		return -EINVAL;
 
-	/* Map back into a voltage to verify we're still in bounds */
-	voltage = rdev->desc->ops->list_voltage(rdev, ret);
-	if (voltage < min_uV || voltage > max_uV)
-		return -EINVAL;
-
 	return ret;
 }
 EXPORT_SYMBOL_GPL(regulator_map_voltage_linear_range);

2.14.3