cleanup, added comments

1 files changed, 14 insertions, 10 deletions

diff --git a/os/hal/ports/NRF51/NRF51822/rng_lld.c b/os/hal/ports/NRF51/NRF51822/rng_lld.c
index 12a75e7..74bba64 100644
--- a/os/hal/ports/NRF51/NRF51822/rng_lld.c
+++ b/os/hal/ports/NRF51/NRF51822/rng_lld.c
@@ -35,7 +35,6 @@
  */
 static const RNGConfig default_config = {
     .digital_error_correction = 1,
-    .power_on_write           = 1,
 };
 
 /*===========================================================================*/
@@ -84,15 +83,16 @@ void rng_lld_start(RNGDriver *rngp) {
   if (rngp->config == NULL)
     rngp->config = &default_config;
 
-  rngp->rng->POWER = 1;
+  rngp->rng->POWER         = 1;
 
   if (rngp->config->digital_error_correction) 
     rngp->rng->CONFIG |=  RNG_CONFIG_DERCEN_Msk;
   else
     rngp->rng->CONFIG &= ~RNG_CONFIG_DERCEN_Msk;
 
-  rngp->rng->INTENSET    = RNG_INTENSET_VALRDY_Msk;
-  rngp->rng->TASKS_START = 1;
+  rngp->rng->EVENTS_VALRDY = 0;
+  rngp->rng->INTENSET      = RNG_INTENSET_VALRDY_Msk;
+  rngp->rng->TASKS_START   = 1;
 }
 
 
@@ -105,7 +105,7 @@ void rng_lld_start(RNGDriver *rngp) {
  */
 void rng_lld_stop(RNGDriver *rngp) {
   rngp->rng->TASKS_STOP = 1;
-  rngp->rng->POWER = 0;
+  rngp->rng->POWER      = 0;
 }
 
 
@@ -121,23 +121,27 @@ void rng_lld_stop(RNGDriver *rngp) {
 msg_t rng_lld_write(RNGDriver *rngp, uint8_t *buf, size_t n,
 		    systime_t timeout) {
   size_t i;
-  if (n == 0)
-    return MSG_OK;
-
-  NRF_RNG->EVENTS_VALRDY = 0;    
 
   for (i = 0 ; i < n ; i++) {
-    /* wait for next byte */
+    /* Wait for byte ready
+     * It take about 677µs to generate a new byte, not sure if
+     * forcing a context switch will be a benefit
+     */
     while (NRF_RNG->EVENTS_VALRDY == 0) {
+      /* Sleep and wakeup on ARM event (interrupt) */
       SCB->SCR |= SCB_SCR_SEVONPEND_Msk;
       __SEV();
       __WFE();
       __WFE();
     }
 
+    /* Read byte */
     buf[i] = (char)NRF_RNG->VALUE;
 
+    /* Mark as read */
     NRF_RNG->EVENTS_VALRDY = 0;
+
+    /* Clear interrupt so we can wake up again */
     nvicClearPending(RNG_IRQn);
   }
   return MSG_OK;