Merge branch 'silicon-errata' into advanced

Implements the recommended workarounds for numerous silicon errata,
reducing power consumption and preventing freezes and hard faults.

Tested-by: Alex Maestas <git@se30.xyz>
Tested-by: Matheus Afonso Martins Moreira <matheus.a.m.moreira@gmail.com>
Tested-on-hardware-by: Alex Maestas <git@se30.xyz>
Tested-on-hardware-by: Matheus Afonso Martins Moreira <matheus.a.m.moreira@gmail.com>
Reviewed-by: Wesley Aptekar-Cassels <me@wesleyac.com>
Reviewed-by: Matheus Afonso Martins Moreira <matheus.a.m.moreira@gmail.com>
Signed-off-by: Matheus Afonso Martins Moreira <matheus.a.m.moreira@gmail.com>
GitHub-Pull-Request: https://github.com/joeycastillo/Sensor-Watch/pull/340
GitHub-Related-Issue: https://github.com/joeycastillo/Sensor-Watch/issues/361
GitHub-Related-Issue: https://github.com/joeycastillo/Sensor-Watch/issues/359
Reference: https://ww1.microchip.com/downloads/aemDocuments/documents/MCU32/ProductDocuments/Errata/SAM-L22-Family-Silicon-Errata-and-Data-Sheet-Clarification-DS80000782.pdf

movement/watch_faces/complication/randonaut_face.c

@@ -357,7 +357,7 @@ static uint32_t _get_true_entropy(void) {
 
     while (!hri_trng_get_INTFLAG_reg(TRNG, TRNG_INTFLAG_DATARDY)); // Wait for TRNG data to be ready
 
-    hri_trng_clear_CTRLA_ENABLE_bit(TRNG);
+    watch_disable_TRNG();
     hri_mclk_clear_APBCMASK_TRNG_bit(MCLK);
     return hri_trng_read_DATA_reg(TRNG); // Read a single 32-bit word from TRNG and return it
     #endif

movement/watch_faces/complication/toss_up_face.c

@@ -255,7 +255,8 @@ uint32_t get_true_entropy(void) {
 
     while (!hri_trng_get_INTFLAG_reg(TRNG, TRNG_INTFLAG_DATARDY)); // Wait for TRNG data to be ready
 
-    hri_trng_clear_CTRLA_ENABLE_bit(TRNG);
+    watch_disable_TRNG();
+
     hri_mclk_clear_APBCMASK_TRNG_bit(MCLK);
     return hri_trng_read_DATA_reg(TRNG); // Read a single 32-bit word from TRNG and return it
     #endif

watch-library/hardware/hal/include/hpl_sleep.h

@@ -70,6 +70,16 @@ extern "C" {
  */
 int32_t _set_sleep_mode(const uint8_t mode);
 
+/**
+ * \brief Get the sleep mode for the device
+ *
+ * This function gets the sleep mode for the device.
+ *
+ * \return the current value of the sleep mode configuration bits
+ */
+int32_t _get_sleep_mode(void);
+
+
 /**
  * \brief Reset MCU
  */

watch-library/hardware/hal/src/hal_sleep.c

@@ -57,6 +57,15 @@ int sleep(const uint8_t mode)
 	if (ERR_NONE != _set_sleep_mode(mode))
 		return ERR_INVALID_ARG;
 
+        // wait for the mode set to actually take, per note in Microchip data
+        // sheet DS60001465, section 19.8.2:
+        //
+        // A small latency happens between the store instruction and actual
+        // writing of the SLEEPCFG register due to bridges. Software has to make
+        // sure the SLEEPCFG register reads the wanted value before issuing WFI
+        // instruction.
+        while(_get_sleep_mode() != mode);
+
 	_go_to_sleep();
 
 	return ERR_NONE;

watch-library/hardware/hpl/pm/hpl_pm.c

@@ -63,6 +63,14 @@ int32_t _set_sleep_mode(const uint8_t mode)
 	return ERR_NONE;
 }
 
+/**
+ * \brief Get the sleep mode for the device
+ */
+int32_t _get_sleep_mode()
+{
+    return hri_pm_read_SLEEPCFG_SLEEPMODE_bf(PM);
+}
+
 /**
  * \brief Set performance level
  */

watch-library/hardware/startup_saml22.c

@@ -220,6 +220,5 @@ void Reset_Handler(void)
  */
 void Dummy_Handler(void)
 {
-    while (1) {
-    }
+    NVIC_SystemReset();
 }

watch-library/hardware/watch/watch_deepsleep.c

@@ -22,6 +22,8 @@
  * SOFTWARE.
  */
 
+#include "hpl_systick_config.h"
+
 #include "watch_extint.h"
 
 // this warning only appears when you `make BOARD=OSO-SWAT-A1-02`. it's annoying,
@@ -158,14 +160,20 @@ void watch_enter_sleep_mode(void) {
     // disable brownout detector interrupt, which could inadvertently wake us up.
     SUPC->INTENCLR.bit.BOD33DET = 1;
 
+    // per Microchip datasheet clarification DS80000782,
+    // work around silicon erratum 1.8.4 by disabling the SysTick interrupt, which is
+    // enabled as part of driver init, before going to sleep.
+    SysTick->CTRL = SysTick->CTRL & ~(CONF_SYSTICK_TICKINT << SysTick_CTRL_TICKINT_Pos);
+
     // disable all pins
     _watch_disable_all_pins_except_rtc();
 
     // enter standby (4); we basically hang out here until an interrupt wakes us.
     sleep(4);
 
-    // and we awake! re-enable the brownout detector
+    // and we awake! re-enable the brownout detector and SysTick interrupt
     SUPC->INTENSET.bit.BOD33DET = 1;
+    SysTick->CTRL = SysTick->CTRL | (CONF_SYSTICK_TICKINT << SysTick_CTRL_TICKINT_Pos);
 
     // call app_setup so the app can re-enable everything we disabled.
     app_setup();

watch-library/hardware/watch/watch_private.c

@@ -35,6 +35,12 @@ void _watch_init(void) {
 
     // Use switching regulator for lower power consumption.
     SUPC->VREG.bit.SEL = 1;
+
+    // per Microchip datasheet clarification DS80000782,
+    // work around silicon erratum 1.7.2, which causes the microcontroller to lock up on leaving standby:
+    // request that the voltage regulator run in standby, and also that it switch to PL0.
+    SUPC->VREG.bit.RUNSTDBY = 1;
+    SUPC->VREG.bit.STDBYPL0 = 1;
     while(!SUPC->STATUS.bit.VREGRDY); // wait for voltage regulator to become ready
 
     // check the battery voltage...
@@ -106,12 +112,21 @@ int getentropy(void *buf, size_t buflen) {
         }
     }
 
-    hri_trng_clear_CTRLA_ENABLE_bit(TRNG);
+    watch_disable_TRNG();
     hri_mclk_clear_APBCMASK_TRNG_bit(MCLK);
 
     return 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);
+}
+
+
 void _watch_enable_tcc(void) {
     // clock TCC0 with the main clock (8 MHz) and enable the peripheral clock.
     hri_gclk_write_PCHCTRL_reg(GCLK, TCC0_GCLK_ID, GCLK_PCHCTRL_GEN_GCLK0_Val | GCLK_PCHCTRL_CHEN);

watch-library/shared/watch/watch.h

@@ -96,4 +96,8 @@ void watch_reset_to_bootloader(void);
   */
 int read(int file, char *ptr, int len);
 
-#endif /* WATCH_H_ */
+/** @brief Disables the TRNG twice in order to work around silicon erratum 1.16.1.
+ */
+void watch_disable_TRNG();
+
+#endif /* WATCH_H_ */

watch-library/simulator/watch/watch_private.c

@@ -57,6 +57,8 @@ void _watch_disable_tcc(void) {}
 
 void _watch_enable_usb(void) {}
 
+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) {
     // TODO: (a2) hook to UI