mos/x86_64: Add UART driver + MU interface

Signed-off-by: Ian Moffett <ian@osmora.org>

6 files changed, 126 insertions, 2 deletions

diff --git a/mos/sys/arch/x86_64/Makefile b/mos/sys/arch/x86_64/Makefile
index c28b067..64dda3e 100644
--- a/mos/sys/arch/x86_64/Makefile
+++ b/mos/sys/arch/x86_64/Makefile
@@ -7,12 +7,16 @@ ASMFILES = $(shell find . -name "*.S")
 ASMOFILES = $(ASMFILES:.S=.S.o)
 MISC_OFILES = $(shell find ../../ -name "*.o")
 
+CFILES = $(shell find . -name "*.c")
+OFILES = $(CFILES:.c=.o)
+
 CC =
 LD =
 
 SYS_CFLAGS =
 CFLAGS =                    	\
-	-I ../../target/inc/		\
+	-I../../target/inc/			\
+	-I../../inc/				\
 	-I../../../../usr/sdk/inc/	\
 	$(SYS_CFLAGS)
 
@@ -20,8 +24,11 @@ LDFLAGS = -Tadmin/mos.lds
 MOS_OUT = ../../sys.mos
 
 .PHONY: all
-all: $(ASMOFILES)
+all: $(OFILES) $(ASMOFILES)
 	$(LD) $(LDFLAGS) $(MISC_OFILES) -o $(MOS_OUT)
 
+%.o: %.c
+	$(CC) $(CFLAGS) -c $< -o $@
+
 %.S.o: %.S
 	$(CC) $(CFLAGS) -c $< -o $@
diff --git a/mos/sys/arch/x86_64/io/uart.c b/mos/sys/arch/x86_64/io/uart.c
new file mode 100644
index 0000000..99c4645
--- /dev/null
+++ b/mos/sys/arch/x86_64/io/uart.c
@@ -0,0 +1,58 @@
+/*
+ * Copyright (c) 2025, Ian Moffett.
+ * Provided under the BSD-3 clause.
+ */
+
+#include <sdk/param.h>
+#include <sdk/types.h>
+#include <mu/uart.h>
+#include <md/uart.h>
+#include <md/pio.h>
+
+#define DEFAULT_PORT UART_COM1
+
+static USHORT commap[] = {
+    UART_COM1, UART_COM2,
+    UART_COM3, UART_COM4
+};
+
+static void
+init_uart(USHORT port)
+{
+    UBYTE reg;
+
+    /* Clear DLAB bit */
+    reg = md_inb(UART_LCR(port));
+    reg &= ~UART_LCR_DLAB;
+    reg &= ~UART_PARITY_MASK;
+    reg |= UART_LCR_STOP;
+    md_outb(UART_LCR(port), reg);
+
+    /* Disable interrupts */
+    md_outb(UART_INTEN(port), 0);
+
+    /* Set DLAB */
+    reg = md_inb(UART_LCR(port));
+    reg |= UART_LCR_DLAB;
+    md_outb(UART_LCR(port), reg);
+
+    /* 38400 baud */
+    md_outb(UART_DIVLOW(port), 0x03);
+    md_outb(UART_DIVHIGH(port), 0x00);
+}
+
+void
+mu_uart_write(const char *s, USIZE len)
+{
+    for (USIZE i = 0; i < len; ++i) {
+        md_outb(DEFAULT_PORT, s[i]);
+    }
+}
+
+void
+mu_uart_init(void)
+{
+    for (int i = 0; i < NELEM(commap); ++i) {
+        init_uart(commap[i]);
+    }
+}
diff --git a/mos/sys/inc/arch/x86_64/uart.h b/mos/sys/inc/arch/x86_64/uart.h
new file mode 100644
index 0000000..1cb6793
--- /dev/null
+++ b/mos/sys/inc/arch/x86_64/uart.h
@@ -0,0 +1,30 @@
+/*
+ * Copyright (c) 2025, Ian Moffett.
+ * Provided under the BSD-3 clause.
+ */
+
+#ifndef _MACHINE_UART_H_
+#define _MACHINE_UART_H_ 1
+
+#include <sdk/param.h>
+
+/* COM ports */
+#define UART_COM1   0x3F8
+#define UART_COM2   0x2F8
+#define UART_COM3   0x3F8
+#define UART_COM4   0x2E8
+#define UART_REG_OFF(COM, REG) ((COM) + (REG))
+
+/* Valid UART 8250 registers */
+#define UART_RXTX(COM)  (COM)
+#define UART_INTEN(COM) UART_REG_OFF((COM), 0x01)
+#define UART_LCR(COM)   UART_REG_OFF((COM), 0x03)
+
+#define UART_DIVLOW(COM) UART_REG_OFF((COM), 0x00)
+#define UART_DIVHIGH(COM) UART_REG_OFF((COM), 0x01)
+
+#define UART_LCR_DLAB       BIT(7)
+#define UART_LCR_STOP       BIT(2)
+#define UART_PARITY_MASK    (0x07 << 3)
+
+#endif  /* !_MACHINE_UART_H_ */
diff --git a/mos/sys/inc/mu/uart.h b/mos/sys/inc/mu/uart.h
new file mode 100644
index 0000000..b38c5f2
--- /dev/null
+++ b/mos/sys/inc/mu/uart.h
@@ -0,0 +1,24 @@
+/*
+ * Copyright (c) 2025, Ian Moffett.
+ * Provided under the BSD-3 clause.
+ */
+
+#ifndef _MU_UART_H_
+#define _MU_UART_H_ 1
+
+#include <sdk/types.h>
+
+/*
+ * Initialize available platform UARTs
+ */
+void mu_uart_init(void);
+
+/*
+ * Write to the default platform UART
+ *
+ * @s: Data to write
+ * @len: Length of data in bytes
+ */
+void mu_uart_writed(const char *s, USIZE len);
+
+#endif  /* !_MU_UART_H_ */
diff --git a/mos/sys/kern/Makefile b/mos/sys/kern/Makefile
index 5abbf16..6a79c9d 100644
--- a/mos/sys/kern/Makefile
+++ b/mos/sys/kern/Makefile
@@ -10,6 +10,7 @@ SYS_CFLAGS =
 CFLAGS = 					\
 	$(SYS_CFLAGS) 			\
 	-I../../../usr/sdk/inc/ \
+	-I../inc/				\
 	-I../target/inc/
 
 .PHONY: all
diff --git a/mos/sys/kern/kern_init.c b/mos/sys/kern/kern_init.c
index 62d73fb..80bfd28 100644
--- a/mos/sys/kern/kern_init.c
+++ b/mos/sys/kern/kern_init.c
@@ -3,10 +3,14 @@
  * Provided under the BSD-3 clause.
  */
 
+#include <mu/uart.h>
+
 /* Forward declaration */
 void kern_main(void);
 
 void
 kern_main(void)
 {
+    /* Initialize platform UARTs */
+    mu_uart_init();
 }