Add RPMSG_VRING_TOTAL_PAYLOAD_SIZE to decide buffer free

Author: kbumsik

cores/arduino/VirtIOSerial.cpp

@@ -122,8 +122,8 @@ size_t VirtIOSerial::readBytes(char *buffer, size_t length)
   uint16_t prev_write_available = virtio_buffer_write_available(&_VirtIOSerialObj.ring);
   const size_t size = virtio_buffer_read(&_VirtIOSerialObj.ring, reinterpret_cast<uint8_t *>(buffer), length);
 
-  if (prev_write_available < RPMSG_VRING_PAYLOAD_SIZE
-      && virtio_buffer_write_available(&_VirtIOSerialObj.ring) >= RPMSG_VRING_PAYLOAD_SIZE) {
+  if (prev_write_available < RPMSG_VRING_TOTAL_PAYLOAD_SIZE
+      && virtio_buffer_write_available(&_VirtIOSerialObj.ring) >= RPMSG_VRING_TOTAL_PAYLOAD_SIZE) {
     MAILBOX_Notify_Rx_Buf_Free();
   }
 
@@ -180,7 +180,7 @@ void VirtIOSerial::rxCallback(VIRT_UART_HandleTypeDef *huart)
   while (size > 0) {
     size -= virtio_buffer_write(&_VirtIOSerialObj.ring, huart->pRxBuffPtr, size);
   }
-  if (virtio_buffer_write_available(&_VirtIOSerialObj.ring) >= RPMSG_VRING_PAYLOAD_SIZE) {
+  if (virtio_buffer_write_available(&_VirtIOSerialObj.ring) >= RPMSG_VRING_TOTAL_PAYLOAD_SIZE) {
     MAILBOX_Notify_Rx_Buf_Free();
   }
 }

cores/arduino/stm32/OpenAMP/openamp_conf.h

@@ -23,6 +23,10 @@
 
 #ifdef VIRTIOCON
 
+/**
+ * Note: Do not remove this. Removing this might not trigger compile error but
+ * the configuration can be significantly different.
+ */
 #include "virtio_config.h"
 
 #ifdef __cplusplus
@@ -121,7 +125,9 @@ extern int __OPENAMP_region_end__[];    /* defined by linker script */
 #define VRING_TX_ADDRESS        -1        /* allocated by Master processor: CA7 */
 #define VRING_BUFF_ADDRESS      -1        /* allocated by Master processor: CA7 */
 #define VRING_ALIGNMENT         16        /* fixed to match with linux constraint */
+#ifndef VRING_NUM_BUFFS
 #define VRING_NUM_BUFFS         16        /* number of rpmsg buffer */
+#endif
 #else
 #error "VRING configuration for the device missing"
 #endif

cores/arduino/stm32/OpenAMP/virtio_buffer.h

@@ -30,7 +30,13 @@
 extern "C" {
 #endif
 
-#define VIRTIO_BUFFER_SIZE (RPMSG_VRING_PAYLOAD_SIZE * 2)
+/**
+ * See virtio_config.h for the size decision.
+ * The multiplier should be at least 1.
+ * If VIRTIO_BUFFER_SIZE is still too big, RPMSG_VRING_TOTAL_PAYLOAD_SIZE
+ * can be reduced by reducing the number of VRING_NUM_BUFFS in virtio_config.h.
+ */
+#define VIRTIO_BUFFER_SIZE (RPMSG_VRING_TOTAL_PAYLOAD_SIZE * 2)
 
 typedef struct {
   uint8_t buffer[VIRTIO_BUFFER_SIZE];

cores/arduino/stm32/OpenAMP/virtio_config.h

@@ -13,6 +13,16 @@
 #define RPMSG_VRING_HEADER_SIZE (16)
 #define RPMSG_VRING_PAYLOAD_SIZE (RPMSG_BUFFER_SIZE - RPMSG_VRING_HEADER_SIZE)
 
+/**
+ * number of rpmsg buffer
+ * This means that a single call of rproc_virtio_notified(rvdev.vdev, VRING1_ID)
+ * will trigger VirtIOSerial::rxCallback() VRING_NUM_BUFFS times at maximum.
+ * A buffer handles VirtIOSerial::rxCallback() requires to be
+ * (RPMSG_VRING_PAYLOAD_SIZE * VRING_NUM_BUFFS) at minimum to prevent overflow.
+ */
+#define VRING_NUM_BUFFS         16
+#define RPMSG_VRING_TOTAL_PAYLOAD_SIZE (RPMSG_VRING_PAYLOAD_SIZE * VRING_NUM_BUFFS)
+
 #if defined (__LOG_TRACE_IO_)
 // OpenAMP trace (log) buffer configuration. See rsc_table.c and Print.cpp
 #define SYSTEM_TRACE_BUF_SZ 2048