iio: st_sensors: verify interrupt event to status

This makes all ST sensor drivers check that they actually have
new data available for the requested channel(s) before claiming
an IRQ, by reading the status register (which is conveniently
the same for all ST sensors) and check that the channel has new
data before proceeding to read it and fill the buffer.

This way sensors can share an interrupt line: it can be flaged
as shared and then the sensor that did not fire will return
NO_IRQ, and the sensor that fired will handle the IRQ and
return IRQ_HANDLED.

Cc: Giuseppe Barba <giuseppe.barba@st.com>
Cc: Denis Ciocca <denis.ciocca@st.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/iio/accel/st_accel_core.c

@@ -332,6 +332,7 @@ static const struct st_sensor_settings st_accel_sensors_settings[] = {
 			.mask_int2 = ST_ACCEL_1_DRDY_IRQ_INT2_MASK,
 			.addr_ihl = ST_ACCEL_1_IHL_IRQ_ADDR,
 			.mask_ihl = ST_ACCEL_1_IHL_IRQ_MASK,
+			.addr_stat_drdy = ST_SENSORS_DEFAULT_STAT_ADDR,
 		},
 		.multi_read_bit = ST_ACCEL_1_MULTIREAD_BIT,
 		.bootime = 2,
@@ -397,6 +398,7 @@ static const struct st_sensor_settings st_accel_sensors_settings[] = {
 			.mask_int2 = ST_ACCEL_2_DRDY_IRQ_INT2_MASK,
 			.addr_ihl = ST_ACCEL_2_IHL_IRQ_ADDR,
 			.mask_ihl = ST_ACCEL_2_IHL_IRQ_MASK,
+			.addr_stat_drdy = ST_SENSORS_DEFAULT_STAT_ADDR,
 		},
 		.multi_read_bit = ST_ACCEL_2_MULTIREAD_BIT,
 		.bootime = 2,
@@ -474,6 +476,7 @@ static const struct st_sensor_settings st_accel_sensors_settings[] = {
 			.mask_int2 = ST_ACCEL_3_DRDY_IRQ_INT2_MASK,
 			.addr_ihl = ST_ACCEL_3_IHL_IRQ_ADDR,
 			.mask_ihl = ST_ACCEL_3_IHL_IRQ_MASK,
+			.addr_stat_drdy = ST_SENSORS_DEFAULT_STAT_ADDR,
 			.ig1 = {
 				.en_addr = ST_ACCEL_3_IG1_EN_ADDR,
 				.en_mask = ST_ACCEL_3_IG1_EN_MASK,
@@ -532,6 +535,7 @@ static const struct st_sensor_settings st_accel_sensors_settings[] = {
 		.drdy_irq = {
 			.addr = ST_ACCEL_4_DRDY_IRQ_ADDR,
 			.mask_int1 = ST_ACCEL_4_DRDY_IRQ_INT1_MASK,
+			.addr_stat_drdy = ST_SENSORS_DEFAULT_STAT_ADDR,
 		},
 		.multi_read_bit = ST_ACCEL_4_MULTIREAD_BIT,
 		.bootime = 2, /* guess */
@@ -583,6 +587,7 @@ static const struct st_sensor_settings st_accel_sensors_settings[] = {
 			.mask_int2 = ST_ACCEL_5_DRDY_IRQ_INT2_MASK,
 			.addr_ihl = ST_ACCEL_5_IHL_IRQ_ADDR,
 			.mask_ihl = ST_ACCEL_5_IHL_IRQ_MASK,
+			.addr_stat_drdy = ST_SENSORS_DEFAULT_STAT_ADDR,
 		},
 		.multi_read_bit = ST_ACCEL_5_MULTIREAD_BIT,
 		.bootime = 2, /* guess */

drivers/iio/common/st_sensors/st_sensors_buffer.c

@@ -58,6 +58,24 @@ irqreturn_t st_sensors_trigger_handler(int irq, void *p)
 	struct iio_dev *indio_dev = pf->indio_dev;
 	struct st_sensor_data *sdata = iio_priv(indio_dev);
 
+	/* If we have a status register, check if this IRQ came from us */
+	if (sdata->sensor_settings->drdy_irq.addr_stat_drdy) {
+		u8 status;
+
+		len = sdata->tf->read_byte(&sdata->tb, sdata->dev,
+			   sdata->sensor_settings->drdy_irq.addr_stat_drdy,
+			   &status);
+		if (len < 0)
+			dev_err(sdata->dev, "could not read channel status\n");
+
+		/*
+		 * If this was not caused by any channels on this sensor,
+		 * return IRQ_NONE
+		 */
+		if (!(status & (u8)indio_dev->active_scan_mask[0]))
+			return IRQ_NONE;
+	}
+
 	len = st_sensors_get_buffer_element(indio_dev, sdata->buffer_data);
 	if (len < 0)
 		goto st_sensors_get_buffer_element_error;

drivers/iio/gyro/st_gyro_core.c

@@ -190,6 +190,7 @@ static const struct st_sensor_settings st_gyro_sensors_settings[] = {
 			 * drain settings, but only for INT1 and not
 			 * for the DRDY line on INT2.
 			 */
+			.addr_stat_drdy = ST_SENSORS_DEFAULT_STAT_ADDR,
 		},
 		.multi_read_bit = ST_GYRO_1_MULTIREAD_BIT,
 		.bootime = 2,
@@ -258,6 +259,7 @@ static const struct st_sensor_settings st_gyro_sensors_settings[] = {
 			 * drain settings, but only for INT1 and not
 			 * for the DRDY line on INT2.
 			 */
+			.addr_stat_drdy = ST_SENSORS_DEFAULT_STAT_ADDR,
 		},
 		.multi_read_bit = ST_GYRO_2_MULTIREAD_BIT,
 		.bootime = 2,
@@ -322,6 +324,7 @@ static const struct st_sensor_settings st_gyro_sensors_settings[] = {
 			 * drain settings, but only for INT1 and not
 			 * for the DRDY line on INT2.
 			 */
+			.addr_stat_drdy = ST_SENSORS_DEFAULT_STAT_ADDR,
 		},
 		.multi_read_bit = ST_GYRO_3_MULTIREAD_BIT,
 		.bootime = 2,

drivers/iio/magnetometer/st_magn_core.c

@@ -484,6 +484,7 @@ static const struct st_sensor_settings st_magn_sensors_settings[] = {
 			.mask_int1 = ST_MAGN_3_DRDY_INT_MASK,
 			.addr_ihl = ST_MAGN_3_IHL_IRQ_ADDR,
 			.mask_ihl = ST_MAGN_3_IHL_IRQ_MASK,
+			.addr_stat_drdy = ST_SENSORS_DEFAULT_STAT_ADDR,
 		},
 		.multi_read_bit = ST_MAGN_3_MULTIREAD_BIT,
 		.bootime = 2,

drivers/iio/pressure/st_pressure_core.c

@@ -226,6 +226,7 @@ static const struct st_sensor_settings st_press_sensors_settings[] = {
 			.mask_int2 = ST_PRESS_LPS331AP_DRDY_IRQ_INT2_MASK,
 			.addr_ihl = ST_PRESS_LPS331AP_IHL_IRQ_ADDR,
 			.mask_ihl = ST_PRESS_LPS331AP_IHL_IRQ_MASK,
+			.addr_stat_drdy = ST_SENSORS_DEFAULT_STAT_ADDR,
 		},
 		.multi_read_bit = ST_PRESS_LPS331AP_MULTIREAD_BIT,
 		.bootime = 2,
@@ -312,6 +313,7 @@ static const struct st_sensor_settings st_press_sensors_settings[] = {
 			.mask_int2 = ST_PRESS_LPS25H_DRDY_IRQ_INT2_MASK,
 			.addr_ihl = ST_PRESS_LPS25H_IHL_IRQ_ADDR,
 			.mask_ihl = ST_PRESS_LPS25H_IHL_IRQ_MASK,
+			.addr_stat_drdy = ST_SENSORS_DEFAULT_STAT_ADDR,
 		},
 		.multi_read_bit = ST_PRESS_LPS25H_MULTIREAD_BIT,
 		.bootime = 2,

include/linux/iio/common/st_sensors.h

@@ -37,6 +37,7 @@
 #define ST_SENSORS_DEFAULT_AXIS_ADDR		0x20
 #define ST_SENSORS_DEFAULT_AXIS_MASK		0x07
 #define ST_SENSORS_DEFAULT_AXIS_N_BIT		3
+#define ST_SENSORS_DEFAULT_STAT_ADDR		0x27
 
 #define ST_SENSORS_MAX_NAME			17
 #define ST_SENSORS_MAX_4WAI			7
@@ -121,6 +122,7 @@ struct st_sensor_bdu {
  * @mask_int2: mask to enable/disable IRQ on INT2 pin.
  * @addr_ihl: address to enable/disable active low on the INT lines.
  * @mask_ihl: mask to enable/disable active low on the INT lines.
+ * @addr_stat_drdy: address to read status of DRDY (data ready) interrupt
  * struct ig1 - represents the Interrupt Generator 1 of sensors.
  * @en_addr: address of the enable ig1 register.
  * @en_mask: mask to write the on/off value for enable.
@@ -131,6 +133,7 @@ struct st_sensor_data_ready_irq {
 	u8 mask_int2;
 	u8 addr_ihl;
 	u8 mask_ihl;
+	u8 addr_stat_drdy;
 	struct {
 		u8 en_addr;
 		u8 en_mask;