uart.c: rx overflow fix and tx simplification

* fixes the clearing of the rx ringbuffer on rx-overflow
* removes tx_level and tx_cts by restricting the ringbuffer
  to at least one slot empty
* agnostic of the details of the tx irq: works for uarts that
  generate tx interrupts on !tx-full or on tx-empty.
* only rx_produce and tx_consume need to be volatile

diff --git a/software/libbase/uart.c b/software/libbase/uart.c
index 30ea5ef32e57f3f234124d44f68fd8c0d5016fd1..6b16ed8a3fd95ac6e93bd4e3d664a70ccb8c2fb5 100644 (file)
--- a/software/libbase/uart.c
+++ b/software/libbase/uart.c
@@ -13,39 +13,37 @@
 
 static char rx_buf[UART_RINGBUFFER_SIZE_RX];
 static volatile unsigned int rx_produce;
-static volatile unsigned int rx_consume;
+static unsigned int rx_consume;
 
 #define UART_RINGBUFFER_SIZE_TX 128
 #define UART_RINGBUFFER_MASK_TX (UART_RINGBUFFER_SIZE_TX-1)
 
 static char tx_buf[UART_RINGBUFFER_SIZE_TX];
 static unsigned int tx_produce;
-static unsigned int tx_consume;
-static volatile int tx_cts;
-static volatile int tx_level;
+static volatile unsigned int tx_consume;
 
 void uart_isr(void)
 {
-       unsigned int stat;
-       
+       unsigned int stat, rx_produce_next;
+
        stat = uart_ev_pending_read();
 
        if(stat & UART_EV_RX) {
                while(!uart_rxempty_read()) {
-                       rx_buf[rx_produce] = uart_rxtx_read();
-                       rx_produce = (rx_produce + 1) & UART_RINGBUFFER_MASK_RX;
+                       rx_produce_next = (rx_produce + 1) & UART_RINGBUFFER_MASK_RX;
+                       if(rx_produce_next != rx_consume) {
+                               rx_buf[rx_produce] = uart_rxtx_read();
+                               rx_produce = rx_produce_next;
+                       }
                        uart_ev_pending_write(UART_EV_RX);
                }
        }
 
        if(stat & UART_EV_TX) {
                uart_ev_pending_write(UART_EV_TX);
-               if(tx_level == 0)
-                       tx_cts = 1;
-               while(tx_level > 0 && !uart_txfull_read()) {
+               while((tx_consume != tx_produce) && !uart_txfull_read()) {
                        uart_rxtx_write(tx_buf[tx_consume]);
                        tx_consume = (tx_consume + 1) & UART_RINGBUFFER_MASK_TX;
-                       tx_level--;
                }
        }
 }
@@ -54,8 +52,13 @@ void uart_isr(void)
 char uart_read(void)
 {
        char c;
-       
-       while(rx_consume == rx_produce);
+
+       if(irq_getie()) {
+               while(rx_consume == rx_produce);
+       } else if (rx_consume == rx_produce) {
+               return 0;
+       }
+
        c = rx_buf[rx_consume];
        rx_consume = (rx_consume + 1) & UART_RINGBUFFER_MASK_RX;
        return c;
@@ -69,45 +72,45 @@ int uart_read_nonblock(void)
 void uart_write(char c)
 {
        unsigned int oldmask;
-       
+       unsigned int tx_produce_next = (tx_produce + 1) & UART_RINGBUFFER_MASK_TX;
+
        if(irq_getie()) {
-               while(tx_level == UART_RINGBUFFER_SIZE_TX);
+               while(tx_produce_next == tx_consume);
+       } else if(tx_produce_next == tx_consume) {
+               return;
        }
-       
-       oldmask = irq_getmask();
-       irq_setmask(0);
 
-       if(tx_cts) {
-               tx_cts = 0;
-               uart_rxtx_write(c);
-       } else {
+       oldmask = irq_getmask();
+       irq_setmask(oldmask & ~(1 << UART_INTERRUPT));
+#if 0
+       while((tx_consume != tx_produce) && !uart_txfull_read()) {
+               uart_rxtx_write(tx_buf[tx_consume]);
+               tx_consume = (tx_consume + 1) & UART_RINGBUFFER_MASK_TX;
+       }
+#endif
+       if((tx_consume != tx_produce) || uart_txfull_read()) {
                tx_buf[tx_produce] = c;
-               tx_produce = (tx_produce + 1) & UART_RINGBUFFER_MASK_TX;
-               tx_level++;
+               tx_produce = tx_produce_next;
+       } else {
+               uart_rxtx_write(c);
        }
        irq_setmask(oldmask);
 }
 
 void uart_init(void)
 {
-       unsigned int mask;
-       
        rx_produce = 0;
        rx_consume = 0;
-       
+
        tx_produce = 0;
        tx_consume = 0;
-       tx_cts = 1;
-       tx_level = 0;
 
        uart_ev_pending_write(uart_ev_pending_read());
        uart_ev_enable_write(UART_EV_TX | UART_EV_RX);
-       mask = irq_getmask();
-       mask |= 1 << UART_INTERRUPT;
-       irq_setmask(mask);
+       irq_setmask(irq_getmask() | (1 << UART_INTERRUPT));
 }
 
 void uart_sync(void)
 {
-       while(!tx_cts);
+       while(tx_consume != tx_produce);
 }