Rewrote the serial port receiver FIFO.

src/device/serial.c

@@ -78,10 +78,13 @@ serial_reset_port(serial_t *dev)
     dev->iir = dev->ier = dev->lcr = dev->fcr = 0;
     dev->fifo_enabled                         = 0;
     dev->xmit_fifo_pos = dev->rcvr_fifo_pos = 0;
+    dev->xmit_fifo_end = dev->rcvr_fifo_end = 0;
     dev->rcvr_fifo_full                     = 0;
     dev->baud_cycles                        = 0;
+    dev->new                                = 0;
+    dev->out_new                            = 0xffff;
     memset(dev->xmit_fifo, 0, 16);
-    memset(dev->rcvr_fifo, 0, 14);
+    memset(dev->rcvr_fifo, 0, 16);
 }
 
 void
@@ -89,7 +92,10 @@ serial_transmit_period(serial_t *dev)
 {
     double ddlab;
 
-    ddlab = (double) dev->dlab;
+    if (dev->dlab != 0x0000)
+        ddlab = (double) dev->dlab;
+    else
+        ddlab = 65536.0;
 
     /* Bit period based on DLAB. */
     dev->transmit_period = (16000000.0 * ddlab) / dev->clock_src;
@@ -145,42 +151,88 @@ serial_clear_timeout(serial_t *dev)
 }
 
 static void
-write_fifo(serial_t *dev, uint8_t dat)
+serial_receive_timer(void *priv)
 {
-    serial_log("write_fifo(%08X, %02X, %i, %i)\n", dev, dat, (dev->type >= SERIAL_16550) && dev->fifo_enabled, dev->rcvr_fifo_pos & 0x0f);
+    serial_t *dev   = (serial_t *) priv;
+#if 0
+    uint16_t old_out_new = dev->out_new;
+#endif
+
+    // serial_log("serial_receive_timer()\n");
+
+    timer_on_auto(&dev->receive_timer, /* dev->bits * */ dev->transmit_period);
 
     if ((dev->type >= SERIAL_16550) && dev->fifo_enabled) {
         /* FIFO mode. */
-        timer_disable(&dev->timeout_timer);
+
-        /* Indicate overrun. */
+        if (dev->out_new != 0xffff) {
-        if (dev->rcvr_fifo_full)
+            /* We have received a byte into the RSR. */
-            dev->lsr |= 0x02;
+
-        else
+            /* Clear FIFO timeout. */
-            dev->rcvr_fifo[dev->rcvr_fifo_pos] = dat;
+            serial_clear_timeout(dev);
-        dev->lsr &= 0xfe;
+
-        dev->int_status &= ~SERIAL_INT_RECEIVE;
+            if (dev->rcvr_fifo_full) {
-        if (dev->rcvr_fifo_pos == (dev->rcvr_fifo_len - 1)) {
+                /* Overrun - just discard the byte in the RSR. */
-            dev->lsr |= 0x01;
+                serial_log("FIFO overrun\n");
-            dev->int_status |= SERIAL_INT_RECEIVE;
+                dev->lsr |= 0x02;
+            } else {
+                /* We can input data into the FIFO. */
+                dev->rcvr_fifo[dev->rcvr_fifo_end] = (uint8_t) (dev->out_new & 0xff);
+                dev->rcvr_fifo_end = (dev->rcvr_fifo_end + 1) & 0x0f;
+
+                serial_log("To FIFO: %02X (%i)\n", (uint8_t) (dev->out_new & 0xff),
+                           abs(dev->rcvr_fifo_end - dev->rcvr_fifo_pos));
+                dev->out_new = 0xffff;
+
+                if (abs(dev->rcvr_fifo_end - dev->rcvr_fifo_pos) >= dev->rcvr_fifo_len) {
+                    /* We have >= trigger level bytes, raise Data Ready interrupt. */
+                    serial_log("We have >= %i bytes in the FIFO, data ready!\n", dev->rcvr_fifo_len);
+                    dev->lsr |= 0x01;
+                    dev->int_status |= SERIAL_INT_RECEIVE;
+                    serial_update_ints(dev);
+                }
+
+                timer_on_auto(&dev->timeout_timer, 4.0 * dev->bits * dev->transmit_period);
+            }
         }
-        if (dev->rcvr_fifo_pos < (dev->rcvr_fifo_len - 1))
+    }
-            dev->rcvr_fifo_pos++;
+
-        else
+    serial_update_ints(dev);
-            dev->rcvr_fifo_full = 1;
+
-        serial_update_ints(dev);
+#if 0
-        timer_on_auto(&dev->timeout_timer, 4.0 * dev->bits * dev->transmit_period);
+    serial_log("FIFO: %i, out_new = %04X, old_out_new = %04X, was_enabled = %i, condition = %i\n",
+               ((dev->type >= SERIAL_16550) && dev->fifo_enabled), dev->out_new,
+               old_out_new, was_enabled,
+               ((dev->type >= SERIAL_16550) && dev->fifo_enabled) ? (dev->rcvr_fifo_pos != dev->rcvr_fifo_end) : dev->new);
+#endif
+}
+
+static void
+write_fifo(serial_t *dev, uint8_t dat)
+{
+    serial_log("write_fifo(%08X, %02X, %i, %i)\n", dev, dat, (dev->type >= SERIAL_16550) && dev->fifo_enabled, dev->rcvr_fifo_pos % dev->rcvr_fifo_len);
+
+    if ((dev->type >= SERIAL_16550) && dev->fifo_enabled) {
+        /* FIFO mode. */
+
+        /* This is the first phase, we are sending the data to the RSR (Receiver Shift
+           Register), from where it's going to get dispatched to the FIFO. */
     } else {
         /* Non-FIFO mode. */
+
         /* Indicate overrun. */
         if (dev->lsr & 0x01)
             dev->lsr |= 0x02;
-        dev->dat = dat;
+
+        /* Raise Data Ready interrupt. */
+        serial_log("To RHR: %02X\n", dat);
         dev->lsr |= 0x01;
         dev->int_status |= SERIAL_INT_RECEIVE;
-        if (dev->lsr & 0x02)
-            dev->int_status |= SERIAL_INT_LSR;
         serial_update_ints(dev);
     }
+
+    /* Do this here, because in non-FIFO mode, this is read directly. */
+    dev->out_new = (uint16_t) dat;
 }
 
 void
@@ -334,6 +386,8 @@ serial_device_timeout(void *priv)
 static void
 serial_update_speed(serial_t *dev)
 {
+    timer_on_auto(&dev->receive_timer, /* dev->bits * */ dev->transmit_period);
+
     if (dev->transmit_enabled & 3)
         timer_on_auto(&dev->transmit_timer, dev->transmit_period);
 
@@ -482,6 +536,7 @@ serial_write(uint16_t addr, uint8_t val, void *p)
                 if (val & 0x02) {
                     memset(dev->rcvr_fifo, 0, 14);
                     dev->rcvr_fifo_pos  = 0;
+                    dev->rcvr_fifo_end  = 0;
                     dev->rcvr_fifo_full = 0;
                 }
                 if (val & 0x04) {
@@ -502,6 +557,8 @@ serial_write(uint16_t addr, uint8_t val, void *p)
                         dev->rcvr_fifo_len = 14;
                         break;
                 }
+                dev->out_new        = 0xffff;
+                dev->new            = 0;
                 serial_log("FIFO now %sabled, receive FIFO length = %i\n", dev->fifo_enabled ? "en" : "dis", dev->rcvr_fifo_len);
             }
             break;
@@ -583,7 +640,7 @@ uint8_t
 serial_read(uint16_t addr, void *p)
 {
     serial_t *dev = (serial_t *) p;
-    uint8_t   i, ret = 0;
+    uint8_t   ret = 0;
 
     cycles -= ISA_CYCLES(8);
 
@@ -594,37 +651,46 @@ serial_read(uint16_t addr, void *p)
                 break;
             }
 
+            /* Clear timeout. */
+            serial_clear_timeout(dev);
+
             if ((dev->type >= SERIAL_16550) && dev->fifo_enabled) {
                 /* FIFO mode. */
 
-                serial_clear_timeout(dev);
+                if (dev->rcvr_fifo_pos != dev->rcvr_fifo_end) {
+                    /* There is data in the FIFO. */
+                    ret = dev->rcvr_fifo[dev->rcvr_fifo_pos];
+                    dev->rcvr_fifo_pos = (dev->rcvr_fifo_pos + 1) & 0x0f;
 
-                ret                 = dev->rcvr_fifo[0];
+                    if (abs(dev->rcvr_fifo_pos - dev->rcvr_fifo_end) < dev->rcvr_fifo_len) {
-                dev->rcvr_fifo_full = 0;
+                        /* Amount of data in the FIFO below trigger level,
+                           clear Data Ready interrupt. */
+                        dev->lsr &= 0xfe;
+                        dev->int_status &= ~SERIAL_INT_RECEIVE;
+                        serial_update_ints(dev);
 
-                for (i = 1; i < 16; i++)
+                        /* Make sure the Data Ready bit of the LSR is set if we still have
-                    dev->rcvr_fifo[i - 1] = dev->rcvr_fifo[i];
+                           bytes left in the FIFO. */
-
+                        if (dev->rcvr_fifo_pos != dev->rcvr_fifo_end) {
-                dev->rcvr_fifo_pos--;
+                            dev->lsr |= 0x01;
-
+                            /* There are bytes left in the FIFO, activate the FIFO Timeout timer. */
-                if (dev->rcvr_fifo_pos > 0) {
+                            timer_on_auto(&dev->timeout_timer, 4.0 * dev->bits * dev->transmit_period);
-                    serial_log("FIFO position %i: read %02X, next %02X\n", dev->rcvr_fifo_pos, ret, dev->rcvr_fifo[0]);
+                        }
-
+                    }
-                    /* At least one byte remains to be read, start the timeout
-                       timer so that a timeout is indicated in case of no read. */
-                    timer_on_auto(&dev->timeout_timer, 4.0 * dev->bits * dev->transmit_period);
-                } else {
-                    dev->lsr &= 0xfe;
-                    dev->int_status &= ~SERIAL_INT_RECEIVE;
-                    serial_update_ints(dev);
                 }
             } else {
-                ret = dev->dat;
+                /* Non-FIFO mode. */
+
+                ret = (uint8_t) (dev->out_new & 0xffff);
+                dev->out_new = 0xffff;
+
+                /* Always clear Data Ready interrupt. */
                 dev->lsr &= 0xfe;
                 dev->int_status &= ~SERIAL_INT_RECEIVE;
                 serial_update_ints(dev);
             }
-            serial_log("Read data: %02X\n", ret);
+
+            // serial_log("Read data: %02X\n", ret);
             break;
         case 1:
             if (dev->lcr & 0x80)
@@ -760,6 +826,34 @@ serial_close(void *priv)
     free(dev);
 }
 
+static void
+serial_reset(void *priv)
+{
+    serial_t *dev = (serial_t *) priv;
+
+    timer_disable(&dev->transmit_timer);
+    timer_disable(&dev->timeout_timer);
+    timer_disable(&dev->receive_timer);
+
+    dev->lsr = dev->thr = dev->mctrl = dev->rcr = 0x00;
+    dev->iir = dev->ier = dev->lcr = dev->msr = 0x00;
+    dev->dat = dev->int_status = dev->scratch = dev->fcr = 0x00;
+    dev->fifo_enabled = dev->rcvr_fifo_len = dev->bits = dev->data_bits = 0x00;
+    dev->baud_cycles = dev->rcvr_fifo_full = dev->txsr = dev->out = 0x00;
+
+    dev->dlab = dev->out_new = dev->new = 0x0000;
+
+    dev->rcvr_fifo_pos = dev->xmit_fifo_pos = dev->rcvr_fifo_end = dev->xmit_fifo_end = 0x00;
+
+    serial_reset_port(dev);
+
+    dev->dlab      = 96;
+    dev->fcr       = 0x06;
+
+    serial_transmit_period(dev);
+    serial_update_speed(dev);
+}
+
 static void *
 serial_init(const device_t *info)
 {
@@ -788,9 +882,11 @@ serial_init(const device_t *info)
         dev->dlab      = 96;
         dev->fcr       = 0x06;
         dev->clock_src = 1843200.0;
-        serial_transmit_period(dev);
         timer_add(&dev->transmit_timer, serial_transmit_timer, dev, 0);
         timer_add(&dev->timeout_timer, serial_timeout_timer, dev, 0);
+        timer_add(&dev->receive_timer, serial_receive_timer, dev, 0);
+        serial_transmit_period(dev);
+        serial_update_speed(dev);
     }
 
     next_inst++;
@@ -818,7 +914,7 @@ const device_t ns8250_device = {
     .local         = SERIAL_8250,
     .init          = serial_init,
     .close         = serial_close,
-    .reset         = NULL,
+    .reset         = serial_reset,
     { .available = NULL },
     .speed_changed = serial_speed_changed,
     .force_redraw  = NULL,
@@ -832,7 +928,7 @@ const device_t ns8250_pcjr_device = {
     .local         = SERIAL_8250_PCJR,
     .init          = serial_init,
     .close         = serial_close,
-    .reset         = NULL,
+    .reset         = serial_reset,
     { .available = NULL },
     .speed_changed = serial_speed_changed,
     .force_redraw  = NULL,
@@ -846,7 +942,7 @@ const device_t ns16450_device = {
     .local         = SERIAL_16450,
     .init          = serial_init,
     .close         = serial_close,
-    .reset         = NULL,
+    .reset         = serial_reset,
     { .available = NULL },
     .speed_changed = serial_speed_changed,
     .force_redraw  = NULL,
@@ -860,7 +956,7 @@ const device_t ns16550_device = {
     .local         = SERIAL_16550,
     .init          = serial_init,
     .close         = serial_close,
-    .reset         = NULL,
+    .reset         = serial_reset,
     { .available = NULL },
     .speed_changed = serial_speed_changed,
     .force_redraw  = NULL,
@@ -874,7 +970,7 @@ const device_t ns16650_device = {
     .local         = SERIAL_16650,
     .init          = serial_init,
     .close         = serial_close,
-    .reset         = NULL,
+    .reset         = serial_reset,
     { .available = NULL },
     .speed_changed = serial_speed_changed,
     .force_redraw  = NULL,
@@ -888,7 +984,7 @@ const device_t ns16750_device = {
     .local         = SERIAL_16750,
     .init          = serial_init,
     .close         = serial_close,
-    .reset         = NULL,
+    .reset         = serial_reset,
     { .available = NULL },
     .speed_changed = serial_speed_changed,
     .force_redraw  = NULL,
@@ -902,7 +998,7 @@ const device_t ns16850_device = {
     .local         = SERIAL_16850,
     .init          = serial_init,
     .close         = serial_close,
-    .reset         = NULL,
+    .reset         = serial_reset,
     { .available = NULL },
     .speed_changed = serial_speed_changed,
     .force_redraw  = NULL,
@@ -916,7 +1012,7 @@ const device_t ns16950_device = {
     .local         = SERIAL_16950,
     .init          = serial_init,
     .close         = serial_close,
-    .reset         = NULL,
+    .reset         = serial_reset,
     { .available = NULL },
     .speed_changed = serial_speed_changed,
     .force_redraw  = NULL,

src/include/86box/serial.h

@@ -53,15 +53,16 @@ typedef struct serial_s {
         dat, int_status, scratch, fcr,
         irq, type, inst, transmit_enabled,
         fifo_enabled, rcvr_fifo_len, bits, data_bits,
-        baud_cycles, rcvr_fifo_full, txsr, pad, msr_set;
+        baud_cycles, rcvr_fifo_full, txsr, out, msr_set, pad, pad0, pad1;
 
-    uint16_t dlab, base_address;
+    uint16_t dlab, base_address, out_new, new;
 
     uint8_t rcvr_fifo_pos, xmit_fifo_pos,
-        pad0, pad1,
+        rcvr_fifo_end, xmit_fifo_end,
         rcvr_fifo[SERIAL_FIFO_SIZE], xmit_fifo[SERIAL_FIFO_SIZE];
 
-    pc_timer_t transmit_timer, timeout_timer;
+    pc_timer_t transmit_timer, timeout_timer,
+               receive_timer;
     double     clock_src, transmit_period;
 
     struct serial_device_s *sd;