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mimxrt: Fix USB CDC handling so it works reliably.

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On i.MX the SysTick IRQ cannot wake the CPU from a WFI so the CPU was
blocked on WFI waiting for USB data in mp_hal_stdin_rx_chr() even though it
had already arrived (because it may arrive just after calling the check
tud_cdc_available()).  This commit fixes this problem by using SEV/WFE to
indicate that there has been a USB event.

The mp_hal_stdout_tx_strn() function is also fixed so that it doesn't
overflow the USB buffers.

Signed-off-by: Damien George <damien@micropython.org>
This commit is contained in:
Damien George 2021-02-12 13:32:27 +11:00
parent c9260dda23
commit f31c6b4840
3 changed files with 11 additions and 10 deletions
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2
ports/mimxrt/board_init.c
View File

@ -92,9 +92,11 @@ void SysTick_Handler(void) {
void USB_OTG1_IRQHandler(void) {
tud_int_handler(0);
tud_task();
__SEV();
}
void USB_OTG2_IRQHandler(void) {
tud_int_handler(1);
tud_task();
__SEV();
}

2
ports/mimxrt/mpconfigport.h
View File

@ -94,7 +94,7 @@ extern const struct _mp_obj_module_t mp_module_utime;
do { \
extern void mp_handle_pending(bool); \
mp_handle_pending(true); \
__WFI(); \
__WFE(); \
} while (0);
#define MICROPY_MAKE_POINTER_CALLABLE(p) ((void *)((mp_uint_t)(p) | 1))

17
ports/mimxrt/mphalport.c
View File

@ -75,7 +75,7 @@ int mp_hal_stdin_rx_chr(void) {
return buf[0];
}
}
__WFI();
MICROPY_EVENT_POLL_HOOK
}
}
@ -83,17 +83,16 @@ void mp_hal_stdout_tx_strn(const char *str, mp_uint_t len) {
if (tud_cdc_connected()) {
for (size_t i = 0; i < len;) {
uint32_t n = len - i;
uint32_t n2 = tud_cdc_write(str + i, n);
if (n2 < n) {
while (!tud_cdc_write_flush()) {
__WFI();
}
if (n > CFG_TUD_CDC_EP_BUFSIZE) {
n = CFG_TUD_CDC_EP_BUFSIZE;
}
while (n > tud_cdc_write_available()) {
__WFE();
}
uint32_t n2 = tud_cdc_write(str + i, n);
tud_cdc_write_flush();
i += n2;
}
while (!tud_cdc_write_flush()) {
__WFI();
}
}
// TODO
// while (len--) {