Fix serial reset hang under FreeRTOS (earlephilhower#1495)

earlephilhower · web-flow · commit 579e366bcf92 · 2023-06-04T13:28:11.000-07:00
The serial port reset logic was calling `sleep_ms()` which ended up doing a task switch...while the other core was frozen and everything was supposed to be locked. Use `busy_wait_ms()` which is a tight loop to delay in the reset portion. Fixes earlephilhower#1486
diff --git a/cores/rp2040/SerialUSB.cpp b/cores/rp2040/SerialUSB.cpp
@@ -188,7 +188,7 @@ static void CheckSerialReset() {
         reset_block(RESETS_RESET_USBCTRL_BITS);
         unreset_block(RESETS_RESET_USBCTRL_BITS);
         // Delay a bit, so the PC can figure out that we have disconnected.
-        sleep_ms(3);
+        busy_wait_ms(3);
         reset_usb_boot(0, 0);
         while (1); // WDT will fire here
     }

Original file line number	Diff line number	Diff line change
`@@ -188,7 +188,7 @@ static void CheckSerialReset() {`
`188`	`188`	`reset_block(RESETS_RESET_USBCTRL_BITS);`
`189`	`189`	`unreset_block(RESETS_RESET_USBCTRL_BITS);`
`190`	`190`	`// Delay a bit, so the PC can figure out that we have disconnected.`
`191`		`- sleep_ms(3);`
	`191`	`+ busy_wait_ms(3);`
`192`	`192`	`reset_usb_boot(0, 0);`
`193`	`193`	`while (1); // WDT will fire here`
`194`	`194`	`}`