esp32/usb: Wake main thread when USB receives data.

pi-anl · dpgeorge · commit 06a7bf967c58 · 2023-11-01T16:27:10.000+11:00
This improves (decreases) the latency on stdin, on SoCs with built-in USB
and using TinyUSB, like S2 and S3.

Signed-off-by: Andrew Leech &lt;andrew.leech@planetinnovation.com.au&gt;
diff --git a/ports/esp32/usb.c b/ports/esp32/usb.c
@@ -40,8 +40,10 @@
 
 static uint8_t usb_rx_buf[CONFIG_TINYUSB_CDC_RX_BUFSIZE];
 
+// This is called from FreeRTOS task "tusb_tsk" in espressif__esp_tinyusb (not an ISR).
 static void usb_callback_rx(int itf, cdcacm_event_t *event) {
-    // TODO: what happens if more chars come in during this function, are they lost?
+    // espressif__esp_tinyusb places tinyusb rx data onto freertos ringbuffer which
+    // this function forwards onto our stdin_ringbuf.
     for (;;) {
         size_t len = 0;
         esp_err_t ret = tinyusb_cdcacm_read(itf, usb_rx_buf, sizeof(usb_rx_buf), &len);
@@ -58,6 +60,7 @@ static void usb_callback_rx(int itf, cdcacm_event_t *event) {
                 ringbuf_put(&stdin_ringbuf, usb_rx_buf[i]);
             }
         }
+        mp_hal_wake_main_task();
     }
 }
 

Original file line number	Diff line number	Diff line change
`@@ -40,8 +40,10 @@`
`40`	`40`
`41`	`41`	`static uint8_t usb_rx_buf[CONFIG_TINYUSB_CDC_RX_BUFSIZE];`
`42`	`42`
	`43`	`+// This is called from FreeRTOS task "tusb_tsk" in espressif__esp_tinyusb (not an ISR).`
`43`	`44`	`static void usb_callback_rx(int itf, cdcacm_event_t *event) {`
`44`		`- // TODO: what happens if more chars come in during this function, are they lost?`
	`45`	`+ // espressif__esp_tinyusb places tinyusb rx data onto freertos ringbuffer which`
	`46`	`+ // this function forwards onto our stdin_ringbuf.`
`45`	`47`	`for (;;) {`
`46`	`48`	`size_t len = 0;`
`47`	`49`	`esp_err_t ret = tinyusb_cdcacm_read(itf, usb_rx_buf, sizeof(usb_rx_buf), &len);`
`@@ -58,6 +60,7 @@ static void usb_callback_rx(int itf, cdcacm_event_t *event) {`
`58`	`60`	`ringbuf_put(&stdin_ringbuf, usb_rx_buf[i]);`
`59`	`61`	`}`
`60`	`62`	`}`
	`63`	`+ mp_hal_wake_main_task();`
`61`	`64`	`}`
`62`	`65`	`}`
`63`	`66`