[PATCH v8 08/26] emul/ns16x50: implement LCR/LSR registers

[dmukhin@xxxxxxxx]

From: Denis Mukhin <dmukhin@xxxxxxxx>

Add LCR/LSR registers implementation to the I/O port handler.

Add implementation of ns16x50_dlab_get() and ns16x50_iir_check_lsi().

Signed-off-by: Denis Mukhin <dmukhin@xxxxxxxx>
---
 xen/common/emul/vuart/ns16x50.c | 23 ++++++++++++++++++++++-
 1 file changed, 22 insertions(+), 1 deletion(-)

diff --git a/xen/common/emul/vuart/ns16x50.c b/xen/common/emul/vuart/ns16x50.c
index 7c5cdc99cfa7..e80815ccf6e2 100644
--- a/xen/common/emul/vuart/ns16x50.c
+++ b/xen/common/emul/vuart/ns16x50.c
@@ -64,6 +64,11 @@ do { \
 #define ns16x50_debug(vdev, fmt, args...) \
     ns16x50_log(3, XENLOG_DEBUG, vdev, fmt, ## args)
 
+/*
+ * Helper register definitions.
+ */
+#define UART_LSR_MASK           (UART_LSR_OE | UART_LSR_BI)
+
 /*
  * Number of supported registers in the UART.
  */
@@ -116,7 +121,7 @@ static inline void ns16x50_unlock(struct vuart_ns16x50 
*vdev,
 
 static bool cf_check ns16x50_iir_check_lsi(const struct vuart_ns16x50 *vdev)
 {
-    return false;
+    return vdev->regs[UART_LSR] & UART_LSR_MASK;
 }
 
 static bool cf_check ns16x50_iir_check_rda(const struct vuart_ns16x50 *vdev)
@@ -245,11 +250,16 @@ static int ns16x50_io_write8(
         }
         break;
 
+    case UART_LCR:
+        regs[UART_LCR] = val;
+        break;
+
     /* NB: Firmware (e.g. OVMF) may rely on SCR presence. */
     case UART_SCR:
         regs[UART_SCR] = val;
         break;
 
+    case UART_LSR: /* RO */
     default:
         rc = -EINVAL;
         break;
@@ -346,6 +356,15 @@ static int ns16x50_io_read8(
         val = ns16x50_iir_get(vdev);
         break;
 
+    case UART_LCR:
+        val = regs[UART_LCR];
+        break;
+
+    case UART_LSR:
+        val = regs[UART_LSR];
+        regs[UART_LSR] = val & ~UART_LSR_MASK;
+        break;
+
     case UART_SCR:
         val = regs[UART_SCR];
         break;
@@ -509,6 +528,8 @@ static void ns16x50_reset(struct vuart_ns16x50 *vdev)
     memset(vdev->regs, 0, sizeof(vdev->regs));
     vdev->irq_asserted = false;
 
+    vdev->regs[UART_LSR] = UART_LSR_THRE | UART_LSR_TEMT;
+
     /* NB: report 115200 baud rate. */
     vdev->regs[NS16X50_REGS_NUM + UART_DLL] = divisor & UINT8_MAX;
     vdev->regs[NS16X50_REGS_NUM + UART_DLM] = (divisor >> 8) & UINT8_MAX;
-- 
2.56.0