iio: adis: add '__adis_enable_irq()' implementation

Add '__adis_enable_irq()' implementation which is the unlocked
version of 'adis_enable_irq()'.
Call '__adis_enable_irq()' instead of 'adis_enable_irq()' from
'__adis_intial_startup()' to keep the expected unlocked functionality.

This fix is needed to remove a deadlock for all devices which are
using 'adis_initial_startup()'. The deadlock occurs because the
same mutex is acquired twice, without releasing it.
The mutex is acquired once inside 'adis_initial_startup()', before
calling '__adis_initial_startup()', and once inside
'adis_enable_irq()', which is called by '__adis_initial_startup()'.
The deadlock is removed by calling '__adis_enable_irq()', instead of
'adis_enable_irq()' from within '__adis_initial_startup()'.

Fixes: b600bd7e ("iio: adis: do not disabe IRQs in 'adis_init()'")
Signed-off-by: Ramona Bolboaca <ramona.bolboaca@analog.com>
Reviewed-by: Nuno Sá <nuno.sa@analog.com>
Link: https://lore.kernel.org/r/20221122082757.449452-2-ramona.bolboaca@analog.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/imu/adis.c

@@ -270,23 +270,19 @@ EXPORT_SYMBOL_NS(adis_debugfs_reg_access, IIO_ADISLIB);
 #endif
 
 /**
- * adis_enable_irq() - Enable or disable data ready IRQ
+ * __adis_enable_irq() - Enable or disable data ready IRQ (unlocked)
  * @adis: The adis device
  * @enable: Whether to enable the IRQ
  *
  * Returns 0 on success, negative error code otherwise
  */
-int adis_enable_irq(struct adis *adis, bool enable)
+int __adis_enable_irq(struct adis *adis, bool enable)
 {
-	int ret = 0;
+	int ret;
 	u16 msc;
 
-	mutex_lock(&adis->state_lock);
-
-	if (adis->data->enable_irq) {
-		ret = adis->data->enable_irq(adis, enable);
-		goto out_unlock;
-	}
+	if (adis->data->enable_irq)
+		return adis->data->enable_irq(adis, enable);
 
 	if (adis->data->unmasked_drdy) {
 		if (enable)
@@ -294,12 +290,12 @@ int adis_enable_irq(struct adis *adis, bool enable)
 		else
 			disable_irq(adis->spi->irq);
 
-		goto out_unlock;
+		return 0;
 	}
 
 	ret = __adis_read_reg_16(adis, adis->data->msc_ctrl_reg, &msc);
 	if (ret)
-		goto out_unlock;
+		return ret;
 
 	msc |= ADIS_MSC_CTRL_DATA_RDY_POL_HIGH;
 	msc &= ~ADIS_MSC_CTRL_DATA_RDY_DIO2;
@@ -308,13 +304,9 @@ int adis_enable_irq(struct adis *adis, bool enable)
 	else
 		msc &= ~ADIS_MSC_CTRL_DATA_RDY_EN;
 
-	ret = __adis_write_reg_16(adis, adis->data->msc_ctrl_reg, msc);
-
-out_unlock:
-	mutex_unlock(&adis->state_lock);
-	return ret;
+	return __adis_write_reg_16(adis, adis->data->msc_ctrl_reg, msc);
 }
-EXPORT_SYMBOL_NS(adis_enable_irq, IIO_ADISLIB);
+EXPORT_SYMBOL_NS(__adis_enable_irq, IIO_ADISLIB);
 
 /**
  * __adis_check_status() - Check the device for error conditions (unlocked)
@@ -445,7 +437,7 @@ int __adis_initial_startup(struct adis *adis)
 	 * with 'IRQF_NO_AUTOEN' anyways.
 	 */
 	if (!adis->data->unmasked_drdy)
-		adis_enable_irq(adis, false);
+		__adis_enable_irq(adis, false);
 
 	if (!adis->data->prod_id_reg)
 		return 0;

include/linux/iio/imu/adis.h

@@ -402,9 +402,20 @@ static inline int adis_update_bits_base(struct adis *adis, unsigned int reg,
 	__adis_update_bits_base(adis, reg, mask, val, sizeof(val));	\
 })
 
-int adis_enable_irq(struct adis *adis, bool enable);
 int __adis_check_status(struct adis *adis);
 int __adis_initial_startup(struct adis *adis);
+int __adis_enable_irq(struct adis *adis, bool enable);
+
+static inline int adis_enable_irq(struct adis *adis, bool enable)
+{
+	int ret;
+
+	mutex_lock(&adis->state_lock);
+	ret = __adis_enable_irq(adis, enable);
+	mutex_unlock(&adis->state_lock);
+
+	return ret;
+}
 
 static inline int adis_check_status(struct adis *adis)
 {