Merge pull request #15804 from haukepetersen/opt_nrf5x_hfxo

cpu/nrf5x: enhance external HF clock source handling to allow for substantial energy savings

cpu/nrf52/radio/nrf802154/nrf802154.c

@@ -27,6 +27,7 @@
 
 #include "cpu.h"
 #include "mutex.h"
+#include "nrf_clock.h"
 
 #include "net/ieee802154.h"
 #include "periph/timer.h"
@@ -247,6 +248,11 @@ static int _init(netdev_t *dev)
     txbuf[0] = 0;
     _state = 0;
 
+    /* the radio need the external HF clock source to be enabled */
+    /* @todo    add proper handling to release the clock whenever the radio is
+     *          idle */
+    clock_hfxo_request();
+
     /* power on peripheral */
     NRF_RADIO->POWER = 1;
 

cpu/nrf52/radio/nrf802154/nrf802154_radio.c

@@ -23,6 +23,7 @@
 
 #include "cpu.h"
 #include "luid.h"
+#include "nrf_clock.h"
 
 #include "net/ieee802154.h"
 #include "periph/timer.h"
@@ -101,6 +102,22 @@ ieee802154_dev_t nrf802154_hal_dev = {
     .driver = &nrf802154_ops,
 };
 
+static void _power_on(void)
+{
+    if (NRF_RADIO->POWER == 0) {
+        clock_hfxo_request();
+        NRF_RADIO->POWER = 1;
+    }
+}
+
+static void _power_off(void)
+{
+    if (NRF_RADIO->POWER == 1) {
+        NRF_RADIO->POWER = 0;
+        clock_hfxo_release();
+    }
+}
+
 static bool _l2filter(uint8_t *mhr)
 {
     uint8_t dst_addr[IEEE802154_LONG_ADDRESS_LEN];
@@ -445,7 +462,8 @@ int nrf802154_init(void)
     (void)result;
     timer_stop(NRF802154_TIMER);
 
-    /* power off peripheral */
+    /* power off peripheral (but do not release the HFXO as we never requested
+     * it so far) */
     NRF_RADIO->POWER = 0;
 
     return 0;
@@ -574,7 +592,7 @@ static int _request_on(ieee802154_dev_t *dev)
     (void) dev;
     _state = STATE_IDLE;
     DEBUG("[nrf802154]: Request to turn on\n");
-    NRF_RADIO->POWER = 1;
+    _power_on();
     /* make sure the radio is disabled/stopped */
     _disable();
     /* we configure it to run in IEEE802.15.4 mode */
@@ -639,7 +657,7 @@ static int _off(ieee802154_dev_t *dev)
 {
     (void) dev;
     DEBUG("[nrf802154] Turning off the radio\n");
-    NRF_RADIO->POWER = 0;
+    _power_off();
     return 0;
 }
 

cpu/nrf5x_common/clock.c

@@ -18,6 +18,9 @@
  */
 
 #include "cpu.h"
+#include "irq.h"
+#include "assert.h"
+#include "nrf_clock.h"
 #include "periph_conf.h"
 
 /* make sure both clocks are configured */
@@ -28,6 +31,8 @@
 #error "Clock init: CLOCK_LFCLK is not defined by your board!"
 #endif
 
+static unsigned _hfxo_requests = 0;
+
 void clock_init_hf(void)
 {
     /* for the nRF51 we can chose the XTAL frequency */
@@ -39,12 +44,36 @@ void clock_init_hf(void)
 #endif
 #endif
 
-#if CLOCK_HFCLK
+    /* allow to always enable the HFXO as non-default option */
-    /* start the HF clock */
+#if CLOCK_HFXO_ONBOOT
+    clock_hfxo_request();
+#endif
+}
+
+void clock_hfxo_request(void)
+{
+    unsigned state = irq_disable();
+    ++_hfxo_requests;
+    if (_hfxo_requests == 1) {
         NRF_CLOCK->EVENTS_HFCLKSTARTED = 0;
         NRF_CLOCK->TASKS_HFCLKSTART = 1;
         while (NRF_CLOCK->EVENTS_HFCLKSTARTED == 0) {}
-#endif
+    }
+    irq_restore(state);
+}
+
+void clock_hfxo_release(void)
+{
+    /* if this function is called while the counter is zero the state in a
+     * driver requesting the HFXO is broken! */
+    assert(_hfxo_requests);
+
+    unsigned state = irq_disable();
+    --_hfxo_requests;
+    if (_hfxo_requests == 0) {
+        NRF_CLOCK->TASKS_HFCLKSTOP = 1;
+    }
+    irq_restore(state);
 }
 
 void clock_start_lf(void)

cpu/nrf5x_common/include/nrf_clock.h

@@ -23,12 +23,33 @@
 extern "C" {
 #endif
 
+/**
+ * @brief   The high frequency clock (HFCLK) uses the internal oscillator per
+ *          default. Setting this define to 1 will enable the HFXO clock source
+ *          on boot so it will always be active.
+ */
+#ifndef CLOCK_HFXO_ONBOOT
+#define CLOCK_HFXO_ONBOOT       0
+#endif
+
 /**
  * @brief   Initialize the high frequency clock (HFCLK) as configured in the
  *          board's periph_conf.h
  */
 void clock_init_hf(void);
 
+/**
+ * @brief   Request the external high frequency crystal (HFXO) as HF clock
+ *          source. If this is the first request, the HFXO will be enabled.
+ */
+void clock_hfxo_request(void);
+
+/**
+ * @brief   Release the use of the HFXO. If this was the last active request,
+ *          the HFXO will be disabled
+ */
+void clock_hfxo_release(void);
+
 /**
  * @brief   Start the low frequency clock (LFCLK) as configured in the board's
  *          periph_conf.

cpu/nrf5x_common/radio/nrfble/nrfble.c

@@ -25,6 +25,7 @@
 
 #include "cpu.h"
 #include "assert.h"
+#include "nrf_clock.h"
 
 #include "nrfble.h"
 #include "net/netdev/ble.h"
@@ -238,6 +239,11 @@ static int _nrfble_init(netdev_t *dev)
     (void)dev;
     assert(_nrfble_dev.driver && _nrfble_dev.event_callback);
 
+    /* the radio need the external HF clock source to be enabled */
+    /* @todo    add proper handling to release the clock whenever the radio is
+     *          idle */
+    clock_hfxo_request();
+
     /* power on the NRFs radio */
     NRF_RADIO->POWER = 1;
     /* configure variable parameters to default values */

cpu/nrf5x_common/radio/nrfmin/nrfmin.c

@@ -24,6 +24,7 @@
 #include "cpu.h"
 #include "mutex.h"
 #include "assert.h"
+#include "nrf_clock.h"
 
 #include "periph_conf.h"
 #include "periph/cpuid.h"
@@ -401,6 +402,11 @@ static int nrfmin_init(netdev_t *dev)
         my_addr ^= cpuid[i] << (8 * (i & 0x01));
     }
 
+    /* the radio need the external HF clock source to be enabled */
+    /* @todo    add proper handling to release the clock whenever the radio is
+     *          idle */
+    clock_hfxo_request();
+
     /* power on the NRFs radio */
     NRF_RADIO->POWER = 1;
     /* load driver specific configuration */