software/libnet/microudp: rearrange send_packet, add comments and remove txlen padding

diff --git a/litex/soc/software/libnet/microudp.c b/litex/soc/software/libnet/microudp.c
index 955340febfc96419887638cc243339aaed869175..3a02f7f9b88607737722211c32f266de38f0ec2a 100644 (file)
--- a/litex/soc/software/libnet/microudp.c
+++ b/litex/soc/software/libnet/microudp.c
@@ -114,14 +114,20 @@ typedef union {
        unsigned char raw[ETHMAC_SLOT_SIZE];
 } ethernet_buffer;
 
+static unsigned int rxslot;
 static unsigned int rxlen;
 static ethernet_buffer *rxbuffer;
+
+static unsigned int txslot;
 static unsigned int txlen;
 static ethernet_buffer *txbuffer;
 
 static void send_packet(void)
 {
-       unsigned int txslot;
+       /* wait buffer to be available */
+       while(!(ethmac_sram_reader_ready_read()));
+
+       /* fill txbuffer */
 #ifndef HW_PREAMBLE_CRC
        unsigned int crc;
        crc = crc32(&txbuffer->raw[8], txlen-8);
@@ -131,7 +137,6 @@ static void send_packet(void)
        txbuffer->raw[txlen+3] = (crc & 0xff000000) >> 24;
        txlen += 4;
 #endif
-       txlen += 4; //FIXME: padding?
 
 #ifdef DEBUG_MICROUDP_TX
        int j;
@@ -141,13 +146,14 @@ static void send_packet(void)
        printf("\n");
 #endif
 
+       /* fill slot, length and send */
+       ethmac_sram_reader_slot_write(txslot);
        ethmac_sram_reader_length_write(txlen);
        ethmac_sram_reader_start_write(1);
-       while(!(ethmac_sram_reader_ready_read()));
-       txslot = ethmac_sram_reader_slot_read();
-       txbuffer = (ethernet_buffer *)(ETHMAC_BASE + ETHMAC_SLOT_SIZE * (ETHMAC_RX_SLOTS + txslot));
+
+       /* update txslot / txbuffer */
        txslot = (txslot+1)%ETHMAC_TX_SLOTS;
-       ethmac_sram_reader_slot_write(txslot);
+       txbuffer = (ethernet_buffer *)(ETHMAC_BASE + ETHMAC_SLOT_SIZE * (ETHMAC_RX_SLOTS + txslot));
 }
 
 static unsigned char my_mac[6];
@@ -415,17 +421,17 @@ void microudp_start(const unsigned char *macaddr, unsigned int ip)
        for(i=0;i<6;i++)
                cached_mac[i] = 0;
 
-       ethmac_sram_reader_slot_write(0);
-       txbuffer = (ethernet_buffer *)(ETHMAC_BASE + ETHMAC_SLOT_SIZE * ETHMAC_RX_SLOTS);
-
+       txslot = 0;
+       ethmac_sram_reader_slot_write(txslot);
+       txbuffer = (ethernet_buffer *)(ETHMAC_BASE + ETHMAC_SLOT_SIZE * (ETHMAC_RX_SLOTS + txslot));
 
-       rxbuffer = (ethernet_buffer *)ETHMAC_BASE;
+       rxslot = 0;
+       rxbuffer = (ethernet_buffer *)(ETHMAC_BASE + ETHMAC_SLOT_SIZE * rxslot);
        rx_callback = (udp_callback)0;
 }
 
 void microudp_service(void)
 {
-       unsigned int rxslot;
        if(ethmac_sram_writer_ev_pending_read() & ETHMAC_EV_SRAM_WRITER) {
                rxslot = ethmac_sram_writer_slot_read();
                rxbuffer = (ethernet_buffer *)(ETHMAC_BASE + ETHMAC_SLOT_SIZE * rxslot);