Fix PIC32 serial driver lost interrupts

git-svn-id: https://nuttx.svn.sourceforge.net/svnroot/nuttx/trunk@4230 7fd9a85b-ad96-42d3-883c-3090e2eb8679

nuttx/arch/mips/src/mips32/up_sigdeliver.c

@@ -115,7 +115,7 @@ void up_sigdeliver(void)
 
   /* Then restore the task interrupt state */
 
-  irqrestore((uint16_t)regs[REG_STATUS]);
+  irqrestore((irqstate_t)regs[REG_STATUS]);
 
   /* Deliver the signals */
 
@@ -137,6 +137,12 @@ void up_sigdeliver(void)
 
   up_ledoff(LED_SIGNAL);
   up_fullcontextrestore(regs);
+
+  /* up_fullcontextrestore() should not return but could if the software
+   * interrupts are disabled.
+   */
+
+  PANIC(OSERR_INTERNAL);
 }
 
 #endif /* !CONFIG_DISABLE_SIGNALS */

nuttx/arch/mips/src/pic32mx/pic32mx-lowconsole.c

@@ -247,16 +247,22 @@ void pic32mx_uartconfigure(uintptr_t uart_base, uint32_t baudrate,
   /* Configure the FIFOs:
    *
    *   RX: Interrupt at 6 of 8 (for 8-deep FIFO) or 3 o 4 (4-deep FIFO)
-   *   TX: Interrupt on FIFO not full
+   *   TX: Interrupt on FIFO empty
    *   Invert transmit polarity.
+   *
+   * NOTE that there are not many options on trigger TX interrupts.  The FIFO not
+   * full might generate better through-put but with a higher interrupt rate.  FIFO
+   * empty should lower the interrupt rate but result in a burstier output.  If
+   * you change this, please read the comment for acknowledging the interrupt in
+   * pic32mx-serial.c
    */
 
 #ifdef UART_STA_URXISEL_RXB6
   pic32mx_putreg(uart_base, PIC32MX_UART_STACLR_OFFSET,
-                 UART_STA_UTXINV    | UART_STA_UTXISEL_TXBNF | UART_STA_URXISEL_RXB6);
+                 UART_STA_UTXINV    | UART_STA_UTXISEL_TXBE | UART_STA_URXISEL_RXB6);
 #else
   pic32mx_putreg(uart_base, PIC32MX_UART_STACLR_OFFSET,
-                 UART_STA_UTXINV    | UART_STA_UTXISEL_TXBNF | UART_STA_URXISEL_RXB3);
+                 UART_STA_UTXINV    | UART_STA_UTXISEL_TXBE | UART_STA_URXISEL_RXB3);
 #endif
 
   /* Configure the FIFO interrupts */

nuttx/arch/mips/src/pic32mx/pic32mx-serial.c

@@ -491,37 +491,71 @@ static int up_interrupt(int irq, void *context)
 
            up_clrpend_irq(priv->irqe);
            lldbg("ERROR: interrrupt STA: %08x\n",
-                 up_serialin(priv, PIC32MX_UART_STA_OFFSET)
+                 up_serialin(priv, PIC32MX_UART_STA_OFFSET));
            handled = true;
         }
 #endif
 
-      /* Handle incoming, receive bytes */
+      /* Handle incoming, received bytes.  The RX FIFO is configured to
+       * interrupt when the RX FIFO is 75% full (that is 6 of 8 for 8-deep
+       * FIFOs or 3 of 4 for 4-deep FIFOS.
+       */
 
       if (up_pending_irq(priv->irqrx))
         {
-            /* Clear the pending RX interrupt */
-
-            up_clrpend_irq(priv->irqrx);
- 
            /* Process incoming bytes */
 
            uart_recvchars(dev);
            handled = true;
+
+           /* Clear the pending RX interrupt if the receive buffer is empty.
+            * Note that interrupts can be lost if the interrupt condition is
+            * still true when the interrupt is cleared.  Keeping the RX
+            * interrupt pending too long is not a problem because the
+            * upper half driver will disable RX interrupts if it no
+            * longer has space to buffer the serial data.
+            */
+
+           if ((up_serialin(priv, PIC32MX_UART_STA_OFFSET) & UART_STA_URXDA) == 0)
+             {
+               up_clrpend_irq(priv->irqrx);
+             }
         }
 
-      /* Handle outgoing, transmit bytes */
+      /* Handle outgoing, transmit bytes  The RT FIFO is configured to
+       * interrupt only when the TX FIFO is empty.  There are not many
+       * options on trigger TX interrupts.  The FIFO-not-full might generate
+       * better through-put but with a higher interrupt rate.  FIFO-empty should
+       * lower the interrupt rate but result in a burstier output.  If
+       * you change this, You will probably need to change the conditions for
+       * clearing the pending TX interrupt below.
+       *
+       * NOTE: When I tried using the FIFO-not-full interrupt trigger, I
+       * had either lost interrupts, or else a window where I might get
+       * infinite interrupts.  The problem is that there is a race condition
+       * with trying to clearing the pending interrupt based on the FIFO
+       * full condition.
+       */
 
       if (up_pending_irq(priv->irqtx))
         {
-            /* Clear the pending RX interrupt */
-
-            up_clrpend_irq(priv->irqtx);
- 
            /* Process outgoing bytes */
 
            uart_xmitchars(dev);
            handled = true;
+
+           /* Clear the pending TX interrupt if the TX FIFO is empty.  
+            * Note that interrupts can be lost if the interrupt condition is
+            * still true when the interrupt is cleared.  Keeping the TX
+            * interrupt pending too long is not a problem:  Upper level logic
+            * will disable the TX interrupt when there is no longer anything
+            * to be sent.
+            */
+
+           if ((up_serialin(priv, PIC32MX_UART_STA_OFFSET) & UART_STA_UTRMT) != 0)
+             {
+               up_clrpend_irq(priv->irqtx);
+             }
         }
     }