drivers/mrf24j40: allow for basic self-test on init

During production it is often desirable for devices to perform
some kind of basic self-test to isolate defects.

For this it is necessary for the initialization not to hang if a
component is faulty / not connected.

This moves an already exising self-test that was previously enabled
as a debug option to an independent compile-time configurable.

It is necessary to call this in _init() before mrf24j40_hardware_reset()
as the reset function uses xtimer_usleep() which will cause another
thread to get scheduled.
If this thread (e.g. rpl or ipv6) then tries to access the netdev, RIOT
will crash.

drivers/include/mrf24j40.h

@@ -115,6 +115,13 @@ extern "C" {
 
 #define MRF24J40_MAX_FRAME_RETRIES      (3U)        /**< Number of frame retries (fixed) */
 
+/**
+ * @defgroup drivers_mrf24j40_config     mrf24j40 driver compile configuration
+ * @ingroup drivers_mrf24j40
+ * @ingroup config
+ * @{
+ */
+
 /**
  * @brief Enable external PA/LNA control
  *
@@ -125,6 +132,19 @@ extern "C" {
 #define MRF24J40_USE_EXT_PA_LNA         (0U)
 #endif
 
+/**
+ * @brief Enable basic self-test on init
+ *
+ * Perform a write / read to a known register on startup to detect
+ * if the device is connected.
+ * Enable this if you want the boot not to hang if the device is
+ * not connected / there are SPI errors.
+ */
+#ifndef MRF24J40_TEST_SPI_CONNECTION
+#define MRF24J40_TEST_SPI_CONNECTION    (0U)
+#endif
+/** @} */
+
 /**
  * @brief   struct holding all params needed for device initialization
  */
@@ -165,8 +185,10 @@ void mrf24j40_setup(mrf24j40_t *dev, const mrf24j40_params_t *params);
  * @brief   Trigger a hardware reset and configure radio with default values
  *
  * @param[in] dev           device to reset
+ *
+ * @return                  0 on success, error otherwise
  */
-void mrf24j40_reset(mrf24j40_t *dev);
+int mrf24j40_reset(mrf24j40_t *dev);
 
 /**
  * @brief   Trigger a clear channel assessment & retrieve RSSI

drivers/mrf24j40/include/mrf24j40_internal.h

@@ -32,8 +32,12 @@ extern "C" {
 
 /**
  * @brief initialization as decribed in datasheet
+ *
+ * @param[in] dev device to initialize
+ *
+ * @return 0 on success, error otherwise
  */
-void mrf24j40_init(mrf24j40_t *dev);
+int mrf24j40_init(mrf24j40_t *dev);
 
 /**
  * @brief Read from a register with a  at address `addr` from device `dev`. Register with 8bit address

drivers/mrf24j40/mrf24j40.c

@@ -40,11 +40,15 @@ void mrf24j40_setup(mrf24j40_t *dev, const mrf24j40_params_t *params)
     dev->params = *params;
 }
 
-void mrf24j40_reset(mrf24j40_t *dev)
+int mrf24j40_reset(mrf24j40_t *dev)
 {
     eui64_t addr_long;
 
-    mrf24j40_init(dev);
+    int res = mrf24j40_init(dev);
+
+    if (res < 0) {
+        return res;
+    }
 
     netdev_ieee802154_reset(&dev->netdev);
 
@@ -72,6 +76,8 @@ void mrf24j40_reset(mrf24j40_t *dev)
     dev->state = 0;
     mrf24j40_set_state(dev, MRF24J40_PSEUDO_STATE_IDLE);
     DEBUG("mrf24j40_reset(): reset complete.\n");
+
+    return 0;
 }
 
 bool mrf24j40_cca(mrf24j40_t *dev, int8_t *rssi)

drivers/mrf24j40/mrf24j40_internal.c

@@ -98,12 +98,9 @@ void mrf24j40_enable_lna(mrf24j40_t *dev)
 }
 #endif /* MRF24J40_USE_EXT_PA_LNA */
 
-void mrf24j40_init(mrf24j40_t *dev)
+int mrf24j40_init(mrf24j40_t *dev)
 {
-
-    mrf24j40_hardware_reset(dev);
-
-#if ENABLE_DEBUG
+#if MRF24J40_TEST_SPI_CONNECTION
     /* Check if MRF24J40 is available */
     uint8_t txmcr = mrf24j40_reg_read_short(dev, MRF24J40_REG_TXMCR);
     if ((txmcr == 0xFF) || (txmcr == 0x00)) {
@@ -117,11 +114,13 @@ void mrf24j40_init(mrf24j40_t *dev)
                       MRF24J40_TXMCR_CSMABF2)) {
             DEBUG("[mrf24j40] Initialization failure, SPI interface communication failed\n");
             /* Return to prevents hangup later in the initialization */
-            return;
+            return -ENODEV;
         }
     }
 #endif
 
+    mrf24j40_hardware_reset(dev);
+
     /* do a soft reset */
     mrf24j40_reg_write_short(dev, MRF24J40_REG_SOFTRST, MRF24J40_SOFTRST_RSTPWR |
                                                         MRF24J40_SOFTRST_RSTBB  |
@@ -165,6 +164,8 @@ void mrf24j40_init(mrf24j40_t *dev)
 
     /* mrf24j40_set_interrupts */
     mrf24j40_reg_write_short(dev, MRF24J40_REG_INTCON, ~(MRF24J40_INTCON_RXIE | MRF24J40_INTCON_TXNIE));
+
+    return 0;
 }
 
 uint8_t mrf24j40_reg_read_short(mrf24j40_t *dev, const uint8_t addr)

drivers/mrf24j40/mrf24j40_netdev.c

@@ -58,7 +58,10 @@ static int _init(netdev_t *netdev)
     gpio_init_int(dev->params.int_pin, GPIO_IN, GPIO_RISING, _irq_handler, dev);
 
     /* reset device to default values and put it into RX state */
-    mrf24j40_reset(dev);
+    if (mrf24j40_reset(dev)) {
+        return -ENODEV;
+    }
+
     return 0;
 }