iio: adis: handle devices that cannot unmask the drdy pin

Some devices can't mask/unmask the data ready pin and in those cases
each driver was just calling '{dis}enable_irq()' to control the trigger
state. This change, moves that handling into the library by introducing
a new boolean in the data structure that tells the library that the
device cannot unmask the pin.

On top of controlling the trigger state, we can also use this flag to
automatically request the IRQ with 'IRQF_NO_AUTOEN' in case it is set.
So far, all users of the library want to start operation with IRQs/DRDY
pin disabled so it should be fairly safe to do this inside the library.

Signed-off-by: Nuno Sá <nuno.sa@analog.com>
Link: https://lore.kernel.org/r/20210903141423.517028-3-nuno.sa@analog.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/imu/adis.c

@@ -286,6 +286,13 @@ int adis_enable_irq(struct adis *adis, bool enable)
 	if (adis->data->enable_irq) {
 		ret = adis->data->enable_irq(adis, enable);
 		goto out_unlock;
+	} else if (adis->data->unmasked_drdy) {
+		if (enable)
+			enable_irq(adis->spi->irq);
+		else
+			disable_irq(adis->spi->irq);
+
+		goto out_unlock;
 	}
 
 	ret = __adis_read_reg_16(adis, adis->data->msc_ctrl_reg, &msc);
@@ -430,7 +437,13 @@ int __adis_initial_startup(struct adis *adis)
 	if (ret)
 		return ret;
 
-	adis_enable_irq(adis, false);
+	/*
+	 * don't bother calling this if we can't unmask the IRQ as in this case
+	 * the IRQ is most likely not yet requested and we will request it
+	 * with 'IRQF_NO_AUTOEN' anyways.
+	 */
+	if (!adis->data->unmasked_drdy)
+		adis_enable_irq(adis, false);
 
 	if (!adis->data->prod_id_reg)
 		return 0;

drivers/iio/imu/adis_trigger.c

@@ -30,6 +30,10 @@ static const struct iio_trigger_ops adis_trigger_ops = {
 static int adis_validate_irq_flag(struct adis *adis)
 {
 	unsigned long direction = adis->irq_flag & IRQF_TRIGGER_MASK;
+
+	/* We cannot mask the interrupt so ensure it's not enabled at request */
+	if (adis->data->unmasked_drdy)
+		adis->irq_flag |= IRQF_NO_AUTOEN;
 	/*
 	 * Typically this devices have data ready either on the rising edge or
 	 * on the falling edge of the data ready pin. This checks enforces that

include/linux/iio/imu/adis.h

@@ -49,6 +49,7 @@ struct adis_timeout {
  * @status_error_mask: Bitmask of errors supported by the device
  * @timeouts: Chip specific delays
  * @enable_irq: Hook for ADIS devices that have a special IRQ enable/disable
+ * @unmasked_drdy: True for devices that cannot mask/unmask the data ready pin
  * @has_paging: True if ADIS device has paged registers
  * @burst_reg_cmd:	Register command that triggers burst
  * @burst_len:		Burst size in the SPI RX buffer. If @burst_max_len is defined,
@@ -78,6 +79,7 @@ struct adis_data {
 	unsigned int status_error_mask;
 
 	int (*enable_irq)(struct adis *adis, bool enable);
+	bool unmasked_drdy;
 
 	bool has_paging;