Zynq: wait for transmission-ready before sending a new packet

Author: htibosch

source/portable/NetworkInterface/Zynq/x_emacpsif.h

@@ -115,7 +115,8 @@
         volatile int rxHead, rxTail;
         volatile int txHead, txTail;
 
-        volatile int txBusy;
+/*      txMutex is replacing the earlier int variable 'txBusy'. */
+		SemaphoreHandle_t txMutex;  /* Replacing the earlier variable 'volatile int txBusy'. */
 
         volatile uint32_t isr_events;
 

source/portable/NetworkInterface/Zynq/x_emacpsif_dma.c

@@ -221,7 +221,9 @@ void emacps_send_handler( void * arg )
      * "isr_events". The task in NetworkInterface will wake-up and do the necessary work.
      */
     xemacpsif->isr_events |= EMAC_IF_TX_EVENT;
-    xemacpsif->txBusy = pdFALSE;
+
+	/* Take the mutex without blocking. */
+	xSemaphoreGiveFromISR( xemacpsif->txMutex, &xHigherPriorityTaskWoken );
 
     if( xEMACTaskHandles[ xEMACIndex ] != NULL )
     {
@@ -252,7 +254,6 @@ XStatus emacps_send_message( xemacpsif_s * xemacpsif,
                              int iReleaseAfterSend )
 {
     int txHead = xemacpsif->txHead;
-    int iHasSent = 0;
     uint32_t ulBaseAddress = xemacpsif->emacps.Config.BaseAddress;
     BaseType_t xEMACIndex = get_xEMACIndex( &xemacpsif->emacps );
     TickType_t xBlockTimeTicks = pdMS_TO_TICKS( 5000U );
@@ -315,8 +316,6 @@ XStatus emacps_send_message( xemacpsif_s * xemacpsif,
         {
         }
 
-        iHasSent = pdTRUE;
-
         txHead++;
 
         if( txHead == ipconfigNIC_N_TX_DESC )
@@ -328,18 +327,24 @@ XStatus emacps_send_message( xemacpsif_s * xemacpsif,
          * accessed as little as possible. */
         xemacpsif->txHead = txHead;
 
+		if( xSemaphoreTake( xemacpsif->txMutex, 200U ) == pdFALSE )
+		{
+			FreeRTOS_printf( ( "emacps_send_message: mutex can not be taken, something is really wrong.\n" ) );
+			/* There is no risk in continuing here. */
+		}
+
         /* Data Synchronization Barrier */
         dsb();
 
-        if( iHasSent == pdTRUE )
         {
-            /* Make STARTTX high */
-            uint32_t ulValue = XEmacPs_ReadReg( ulBaseAddress, XEMACPS_NWCTRL_OFFSET );
-            /* Start transmit */
-            xemacpsif->txBusy = pdTRUE;
-            XEmacPs_WriteReg( ulBaseAddress, XEMACPS_NWCTRL_OFFSET, ( ulValue | XEMACPS_NWCTRL_STARTTX_MASK ) );
-            /* Read back the register to make sure the data is flushed. */
-            ( void ) XEmacPs_ReadReg( ulBaseAddress, XEMACPS_NWCTRL_OFFSET );
+			/* Make STARTTX high */
+			uint32_t ulValue = XEmacPs_ReadReg( ulBaseAddress, XEMACPS_NWCTRL_OFFSET );
+			/* Set the Start transmit bit. */
+			ulValue |= XEMACPS_NWCTRL_STARTTX_MASK;
+			XEmacPs_WriteReg( ulBaseAddress, XEMACPS_NWCTRL_OFFSET, ulValue );
+			/* Read back the register to make sure the data is flushed. */
+			( void ) XEmacPs_ReadReg( ulBaseAddress, XEMACPS_NWCTRL_OFFSET );
+			/* The mutex will be given later on in emacps_send_handler(). */
         }
 
         dsb();
@@ -685,6 +690,15 @@ XStatus init_dma( xemacpsif_s * xemacpsif )
         configASSERT( xTXDescriptorSemaphores[ xEMACIndex ] );
     }
 
+	if( xemacpsif->txMutex == NULL )
+	{
+		/* txMutex can always be taken, except between sending a packet
+		 * and receiving the TX RX interrupt. */
+		xemacpsif->txMutex = xSemaphoreCreateBinary();
+		xSemaphoreGive( xemacpsif->txMutex );
+		configASSERT( xemacpsif->txMutex != NULL );
+	}
+
     /*
      * Allocate RX descriptors, 1 RxBD at a time.
      */