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annotate TRNG erratum, address review comment

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This commit is contained in:
Alex Maestas
2024-01-22 00:30:25 +00:00
parent de692e05e2
commit 83a0e4e992
5 changed files with 12 additions and 16 deletions
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14
watch-library/hardware/watch/watch_private.c
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@@ -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);
}

8
watch-library/shared/watch/watch.h
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@@ -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_ */

2
watch-library/simulator/watch/watch_private.c
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@@ -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) {