litex: ensure we don't re-enable interrups during ISR

During an interrupt handler, interrupts are implicitly disabled. They
will be re-enabled when the interrupt handler returns.

Due to some changes that were made, varous calls will re-enable
interrupts after they're finished. Examples of this include calling
`CALLBACK_CRITICAL_END` and getting the number of ticks with
`port_get_raw_ticks()`.

This patch prevents this from happening by doing two things:

1. Use standard calls in `port_get_raw_ticks()` to disable and re-enable
interrupts, preventing nesting issues, and
2. Increase the nesting count inside `isr()`, reflecting the implicit
call that is made by hardware when an interrupt is handled

This helps to address #3841.

Signed-off-by: Sean Cross <sean@xobs.io>

1 files changed, 4 insertions, 2 deletions

diff --git a/ports/litex/supervisor/port.c b/ports/litex/supervisor/port.c
index 02617b9af..9897fa397 100644
--- a/ports/litex/supervisor/port.c
+++ b/ports/litex/supervisor/port.c
@@ -32,6 +32,8 @@
 #include "irq.h"
 #include "csr.h"
 
+#include "shared-bindings/microcontroller/__init__.h"
+
 // Global millisecond tick count. 1024 per second because most RTCs are clocked with 32.768khz
 // crystals.
 volatile uint64_t raw_ticks = 0;
@@ -129,9 +131,9 @@ uint32_t port_get_saved_word(void) {
 
 uint64_t port_get_raw_ticks(uint8_t* subticks) {
     // Reading 64 bits may take two loads, so turn of interrupts while we do it.
-    irq_setie(false);
+    common_hal_mcu_disable_interrupts();
     uint64_t raw_tick_snapshot = raw_ticks;
-    irq_setie(true);
+    common_hal_mcu_enable_interrupts();
     return raw_tick_snapshot;
 }