milkymist_uart: support new core version

The new version of the uart core introduces status and control bits.

Signed-off-by: Michael Walle <michael@walle.cc>

hw/milkymist-hw.h

@@ -5,15 +5,14 @@
 #include "qdev-addr.h"
 
 static inline DeviceState *milkymist_uart_create(target_phys_addr_t base,
-        qemu_irq rx_irq, qemu_irq tx_irq)
+        qemu_irq irq)
 {
     DeviceState *dev;
 
     dev = qdev_create(NULL, "milkymist-uart");
     qdev_init_nofail(dev);
     sysbus_mmio_map(sysbus_from_qdev(dev), 0, base);
-    sysbus_connect_irq(sysbus_from_qdev(dev), 0, rx_irq);
-    sysbus_connect_irq(sysbus_from_qdev(dev), 1, tx_irq);
+    sysbus_connect_irq(sysbus_from_qdev(dev), 0, irq);
 
     return dev;
 }

hw/milkymist-uart.c

@@ -30,19 +30,53 @@
 enum {
     R_RXTX = 0,
     R_DIV,
+    R_STAT,
+    R_CTRL,
+    R_DBG,
     R_MAX
 };
 
+enum {
+    STAT_THRE   = (1<<0),
+    STAT_RX_EVT = (1<<1),
+    STAT_TX_EVT = (1<<2),
+};
+
+enum {
+    CTRL_RX_IRQ_EN = (1<<0),
+    CTRL_TX_IRQ_EN = (1<<1),
+    CTRL_THRU_EN   = (1<<2),
+};
+
+enum {
+    DBG_BREAK_EN = (1<<0),
+};
+
 struct MilkymistUartState {
     SysBusDevice busdev;
     CharDriverState *chr;
-    qemu_irq rx_irq;
-    qemu_irq tx_irq;
+    qemu_irq irq;
 
     uint32_t regs[R_MAX];
 };
 typedef struct MilkymistUartState MilkymistUartState;
 
+static void uart_update_irq(MilkymistUartState *s)
+{
+    int rx_event = s->regs[R_STAT] & STAT_RX_EVT;
+    int tx_event = s->regs[R_STAT] & STAT_TX_EVT;
+    int rx_irq_en = s->regs[R_CTRL] & CTRL_RX_IRQ_EN;
+    int tx_irq_en = s->regs[R_CTRL] & CTRL_TX_IRQ_EN;
+
+    if ((rx_irq_en && rx_event) || (tx_irq_en && tx_event)) {
+        trace_milkymist_uart_raise_irq();
+        qemu_irq_raise(s->irq);
+    } else {
+        trace_milkymist_uart_lower_irq();
+        qemu_irq_lower(s->irq);
+    }
+}
+
 static uint32_t uart_read(void *opaque, target_phys_addr_t addr)
 {
     MilkymistUartState *s = opaque;
@@ -51,7 +85,12 @@ static uint32_t uart_read(void *opaque, target_phys_addr_t addr)
     addr >>= 2;
     switch (addr) {
     case R_RXTX:
+        r = s->regs[addr];
+        break;
     case R_DIV:
+    case R_STAT:
+    case R_CTRL:
+    case R_DBG:
         r = s->regs[addr];
         break;
 
@@ -79,18 +118,26 @@ static void uart_write(void *opaque, target_phys_addr_t addr, uint32_t value)
         if (s->chr) {
             qemu_chr_fe_write(s->chr, &ch, 1);
         }
-        trace_milkymist_uart_pulse_irq_tx();
-        qemu_irq_pulse(s->tx_irq);
+        s->regs[R_STAT] |= STAT_TX_EVT;
         break;
     case R_DIV:
+    case R_CTRL:
+    case R_DBG:
         s->regs[addr] = value;
         break;
 
+    case R_STAT:
+        /* write one to clear bits */
+        s->regs[addr] &= ~(value & (STAT_RX_EVT | STAT_TX_EVT));
+        break;
+
     default:
         error_report("milkymist_uart: write access to unknown register 0x"
                 TARGET_FMT_plx, addr << 2);
         break;
     }
+
+    uart_update_irq(s);
 }
 
 static CPUReadMemoryFunc * const uart_read_fn[] = {
@@ -109,14 +156,19 @@ static void uart_rx(void *opaque, const uint8_t *buf, int size)
 {
     MilkymistUartState *s = opaque;
 
+    assert(!(s->regs[R_STAT] & STAT_RX_EVT));
+
+    s->regs[R_STAT] |= STAT_RX_EVT;
     s->regs[R_RXTX] = *buf;
-    trace_milkymist_uart_pulse_irq_rx();
-    qemu_irq_pulse(s->rx_irq);
+
+    uart_update_irq(s);
 }
 
 static int uart_can_rx(void *opaque)
 {
-    return 1;
+    MilkymistUartState *s = opaque;
+
+    return !(s->regs[R_STAT] & STAT_RX_EVT);
 }
 
 static void uart_event(void *opaque, int event)
@@ -131,6 +183,9 @@ static void milkymist_uart_reset(DeviceState *d)
     for (i = 0; i < R_MAX; i++) {
         s->regs[i] = 0;
     }
+
+    /* THRE is always set */
+    s->regs[R_STAT] = STAT_THRE;
 }
 
 static int milkymist_uart_init(SysBusDevice *dev)
@@ -138,8 +193,7 @@ static int milkymist_uart_init(SysBusDevice *dev)
     MilkymistUartState *s = FROM_SYSBUS(typeof(*s), dev);
     int uart_regs;
 
-    sysbus_init_irq(dev, &s->rx_irq);
-    sysbus_init_irq(dev, &s->tx_irq);
+    sysbus_init_irq(dev, &s->irq);
 
     uart_regs = cpu_register_io_memory(uart_read_fn, uart_write_fn, s,
             DEVICE_NATIVE_ENDIAN);

hw/milkymist.c

@@ -146,7 +146,7 @@ milkymist_init(ram_addr_t ram_size_not_used,
         exit(1);
     }
 
-    milkymist_uart_create(0x60000000, irq[0], irq[1]);
+    milkymist_uart_create(0x60000000, irq[0]);
     milkymist_sysctl_create(0x60001000, irq[2], irq[3], irq[4],
             80000000, 0x10014d31, 0x0000041f, 0x00000001);
     milkymist_hpdmc_create(0x60002000);

trace-events

@@ -444,8 +444,8 @@ milkymist_tmu2_pulse_irq(void) "Pulse IRQ"
 # hw/milkymist-uart.c
 milkymist_uart_memory_read(uint32_t addr, uint32_t value) "addr %08x value %08x"
 milkymist_uart_memory_write(uint32_t addr, uint32_t value) "addr %08x value %08x"
-milkymist_uart_pulse_irq_rx(void) "Pulse IRQ RX"
-milkymist_uart_pulse_irq_tx(void) "Pulse IRQ TX"
+milkymist_uart_raise_irq(void) "Raise IRQ"
+milkymist_uart_lower_irq(void) "Lower IRQ"
 
 # hw/milkymist-vgafb.c
 milkymist_vgafb_memory_read(uint32_t addr, uint32_t value) "addr %08x value %08x"