annotate TRNG erratum, address review comment

3 files changed, 10 insertions, 14 deletions

diff --git a/watch-library/hardware/watch/watch_private.c b/watch-library/hardware/watch/watch_private.c
index 20f4ee54..1a33e5c5 100644
--- a/watch-library/hardware/watch/watch_private.c
+++ b/watch-library/hardware/watch/watch_private.c
@@ -110,18 +110,18 @@ int getentropy(void *buf, size_t buflen) {
         }
     }
 
-    watch_disable_TRNG(TRNG);
+    watch_disable_TRNG();
     hri_mclk_clear_APBCMASK_TRNG_bit(MCLK);
 
     return 0;
 }
 
-void watch_disable_TRNG(Trng *hw) {
-    hri_trng_clear_CTRLA_ENABLE_bit(hw);
-    // silicon erratum: the TRNG may leave internal components powered after disable.
-    // the workaround is to clear the register twice.
-    hri_trng_write_CTRLA_reg(hw, 0);
-    hri_trng_write_CTRLA_reg(hw, 0);
+void watch_disable_TRNG() {
+    // per Microchip datasheet clarification DS80000782,
+    // silicon erratum 1.16.1 indicates that the TRNG may leave internal components powered after being disabled.
+    // the workaround is to disable the TRNG by clearing the control register, twice.
+    hri_trng_write_CTRLA_reg(TRNG, 0);
+    hri_trng_write_CTRLA_reg(TRNG, 0);
 }
 
 
diff --git a/watch-library/shared/watch/watch.h b/watch-library/shared/watch/watch.h
index 8ede1f63..d23954ec 100644
--- a/watch-library/shared/watch/watch.h
+++ b/watch-library/shared/watch/watch.h
@@ -96,12 +96,8 @@ void watch_reset_to_bootloader(void);
   */
 int read(int file, char *ptr, int len);
 
-#ifdef __EMSCRIPTEN__
-typedef void* Trng;
-#endif
-
-/** @brief Disables the TRNG, working around a silicon erratum.
+/** @brief Disables the TRNG twice in order to work around silicon erratum 1.16.1.
  */
-void watch_disable_TRNG(Trng* hw);
+void watch_disable_TRNG();
 
 #endif /* WATCH_H_ */
diff --git a/watch-library/simulator/watch/watch_private.c b/watch-library/simulator/watch/watch_private.c
index 509a30b9..03e1f08b 100644
--- a/watch-library/simulator/watch/watch_private.c
+++ b/watch-library/simulator/watch/watch_private.c
@@ -57,7 +57,7 @@ void _watch_disable_tcc(void) {}
 
 void _watch_enable_usb(void) {}
 
-void watch_disable_TRNG(Trng* hw) {}
+void watch_disable_TRNG() {}
 
 // this function ends up getting called by printf to log stuff to the USB console.
 int _write(int file, char *ptr, int len) {