Input: drv260x - fix magnitude handling

First of all, previously the 16-bit magnitude was written as-is to the
device which actually discarded the upper 8 bits since the device has
8-bit registers only. This meant that a strong_magnitude of 0xFF00 would
result in 0. To correct this shift the strong_magnitude / weak_magnitude
input values so we discard the lower 8 bits and keep the upper bits
instead.

Secondly the RTP mode that is used by default interprets the values as
signed (2s complement), so 0x81 = 0%, 0x00 = 50%, 0x7F = 100%. This
doesn't match the FF_RUMBLE interface at all, so let's tell the device
to interpret the data as unsigned instead which gets us 0x00 = 0% and
0xFF = 100%.

As last change switch ERM to using "Closed-Loop Mode, Unidirectional"
instead of "Open-Loop Mode" since it's recommended by the datasheet
compared to open loop and better matches our use case of 0% - 100%
vibration.
Signed-off-by: Luca Weiss <luca@z3ntu.xyz>
Link: https://lore.kernel.org/r/20230430-drv260x-improvements-v1-4-1fb28b4cc698@z3ntu.xyzSigned-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

drivers/input/misc/drv260x.c

@@ -186,7 +186,7 @@ struct drv260x_data {
 	struct work_struct work;
 	struct gpio_desc *enable_gpio;
 	struct regulator *regulator;
-	u32 magnitude;
+	u8 magnitude;
 	u32 mode;
 	u32 library;
 	int rated_voltage;
@@ -237,10 +237,11 @@ static int drv260x_haptics_play(struct input_dev *input, void *data,
 
 	haptics->mode = DRV260X_LRA_NO_CAL_MODE;
 
+	/* Scale u16 magnitude into u8 register value */
 	if (effect->u.rumble.strong_magnitude > 0)
-		haptics->magnitude = effect->u.rumble.strong_magnitude;
+		haptics->magnitude = effect->u.rumble.strong_magnitude >> 8;
 	else if (effect->u.rumble.weak_magnitude > 0)
-		haptics->magnitude = effect->u.rumble.weak_magnitude;
+		haptics->magnitude = effect->u.rumble.weak_magnitude >> 8;
 	else
 		haptics->magnitude = 0;
 
@@ -266,7 +267,7 @@ static void drv260x_close(struct input_dev *input)
 
 static const struct reg_sequence drv260x_lra_cal_regs[] = {
 	{ DRV260X_MODE, DRV260X_AUTO_CAL },
-	{ DRV260X_CTRL3, DRV260X_NG_THRESH_2 },
+	{ DRV260X_CTRL3, DRV260X_NG_THRESH_2 | DRV260X_RTP_UNSIGNED_DATA },
 	{ DRV260X_FEEDBACK_CTRL, DRV260X_FB_REG_LRA_MODE |
 		DRV260X_BRAKE_FACTOR_4X | DRV260X_LOOP_GAIN_HIGH },
 };
@@ -284,7 +285,7 @@ static const struct reg_sequence drv260x_lra_init_regs[] = {
 		DRV260X_BEMF_GAIN_3 },
 	{ DRV260X_CTRL1, DRV260X_STARTUP_BOOST },
 	{ DRV260X_CTRL2, DRV260X_SAMP_TIME_250 },
-	{ DRV260X_CTRL3, DRV260X_NG_THRESH_2 | DRV260X_ANALOG_IN },
+	{ DRV260X_CTRL3, DRV260X_NG_THRESH_2 | DRV260X_RTP_UNSIGNED_DATA | DRV260X_ANALOG_IN },
 	{ DRV260X_CTRL4, DRV260X_AUTOCAL_TIME_500MS },
 };
 
@@ -299,7 +300,7 @@ static const struct reg_sequence drv260x_erm_cal_regs[] = {
 	{ DRV260X_CTRL1, DRV260X_STARTUP_BOOST },
 	{ DRV260X_CTRL2, DRV260X_SAMP_TIME_250 | DRV260X_BLANK_TIME_75 |
 		DRV260X_IDISS_TIME_75 },
-	{ DRV260X_CTRL3, DRV260X_NG_THRESH_2 | DRV260X_ERM_OPEN_LOOP },
+	{ DRV260X_CTRL3, DRV260X_NG_THRESH_2 | DRV260X_RTP_UNSIGNED_DATA },
 	{ DRV260X_CTRL4, DRV260X_AUTOCAL_TIME_500MS },
 };