hwmon: lis3: Power on corrections

Sometimes lis3 chip seems to fail to setup factory tuning at boot up.
This probably happens if there is some odd power ramp down ramp up sequence
for example in device restart. Set boot bit in control2 register to
trig boot sequence manually and wait until it is finished.
Signed-off-by: Samu Onkalo <samu.p.onkalo@nokia.com>
Acked-by: Jonathan Cameron <jic23@cam.ac.uk>
Acked-by: Eric Piel <eric.piel@tremplin-utc.net>
Signed-off-by: Guenter Roeck <guenter.roeck@ericsson.com>

drivers/hwmon/lis3lv02d.c

@@ -307,19 +307,22 @@ void lis3lv02d_poweron(struct lis3lv02d *lis3)
 
 	lis3->init(lis3);
 
-	/* LIS3 power on delay is quite long */
-	msleep(lis3->pwron_delay / lis3lv02d_get_odr());
-
 	/*
 	 * Common configuration
 	 * BDU: (12 bits sensors only) LSB and MSB values are not updated until
 	 *      both have been read. So the value read will always be correct.
+	 * Set BOOT bit to refresh factory tuning values.
 	 */
-	if (lis3->whoami ==  WAI_12B) {
-		lis3->read(lis3, CTRL_REG2, &reg);
-		reg |= CTRL2_BDU;
-		lis3->write(lis3, CTRL_REG2, reg);
-	}
+	lis3->read(lis3, CTRL_REG2, &reg);
+	if (lis3->whoami ==  WAI_12B)
+		reg |= CTRL2_BDU | CTRL2_BOOT;
+	else
+		reg |= CTRL2_BOOT_8B;
+	lis3->write(lis3, CTRL_REG2, reg);
+
+	/* LIS3 power on delay is quite long */
+	msleep(lis3->pwron_delay / lis3lv02d_get_odr());
+
 	if (lis3->reg_ctrl)
 		lis3_context_restore(lis3);
 }

drivers/hwmon/lis3lv02d.h

@@ -150,6 +150,7 @@ enum lis3lv02d_ctrl4_3dc {
 enum lis302d_ctrl2 {
 	HP_FF_WU2	= 0x08,
 	HP_FF_WU1	= 0x04,
+	CTRL2_BOOT_8B   = 0x40,
 };
 
 enum lis3lv02d_ctrl3 {