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zephyr/src: Increase UART input buffer to 512 bytes and reduce latency.

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There are two changes here:

1. Increase the UART input bufffer to 512 bytes.  That's necessary to get
   basic REPL reliability tests working, and helps improve `mpremote`
   usage, eg copying large files.

2. Remove `uart_sem` semaphore.  This is no longer needed because
   `zephyr_getchar()` should be fully non-blocking and have as low a
   latency as possible.  `mp_hal_stdin_rx_chr()` (which calls
   `zephyr_getchar`) already uses `MICROPY_EVENT_POLL_HOOK` to get
   an efficient wait, and doing an extra wait and check for the
   semaphore in `zephyr_getchar()` just introduces unnecessary latency and
   can lead to slower input, and potentially overflowing the UART input
   buffer.

Signed-off-by: Damien George <damien@micropython.org>
This commit is contained in:
Damien George 2025-06-23 12:56:35 +10:00
parent 4951a06bbb
commit 6a53319336
1 changed files with 3 additions and 9 deletions
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12
ports/zephyr/src/zephyr_getchar.c
View file

@ -23,12 +23,10 @@
extern int mp_interrupt_char; extern int mp_interrupt_char;
void mp_sched_keyboard_interrupt(void); void mp_sched_keyboard_interrupt(void);
void mp_hal_signal_event(void); void mp_hal_signal_event(void);
void mp_hal_wait_sem(struct k_sem *sem, uint32_t timeout_ms);
static struct k_sem uart_sem; #define UART_BUFSIZE (512)
#define UART_BUFSIZE 256
static uint8_t uart_ringbuf[UART_BUFSIZE]; static uint8_t uart_ringbuf[UART_BUFSIZE];
static uint8_t i_get, i_put; static uint16_t i_get, i_put;
static int console_irq_input_hook(uint8_t ch) { static int console_irq_input_hook(uint8_t ch) {
int i_next = (i_put + 1) & (UART_BUFSIZE - 1); int i_next = (i_put + 1) & (UART_BUFSIZE - 1);
@ -44,8 +42,6 @@ static int console_irq_input_hook(uint8_t ch) {
uart_ringbuf[i_put] = ch; uart_ringbuf[i_put] = ch;
i_put = i_next; i_put = i_next;
} }
// printk("%x\n", ch);
k_sem_give(&uart_sem);
return 1; return 1;
} }
@ -55,8 +51,7 @@ int zephyr_getchar_check(void) {
} }
int zephyr_getchar(void) { int zephyr_getchar(void) {
mp_hal_wait_sem(&uart_sem, 0); if (i_get != i_put) {
if (k_sem_take(&uart_sem, K_MSEC(0)) == 0) {
unsigned int key = irq_lock(); unsigned int key = irq_lock();
int c = (int)uart_ringbuf[i_get++]; int c = (int)uart_ringbuf[i_get++];
i_get &= UART_BUFSIZE - 1; i_get &= UART_BUFSIZE - 1;
@ -67,7 +62,6 @@ int zephyr_getchar(void) {
} }
void zephyr_getchar_init(void) { void zephyr_getchar_init(void) {
k_sem_init(&uart_sem, 0, UINT_MAX);
uart_console_in_debug_hook_install(console_irq_input_hook); uart_console_in_debug_hook_install(console_irq_input_hook);
// All NULLs because we're interested only in the callback above // All NULLs because we're interested only in the callback above
uart_register_input(NULL, NULL, NULL); uart_register_input(NULL, NULL, NULL);