uart support

2 files changed, 217 insertions, 0 deletions

diff --git a/uart/uart.c b/uart/uart.c
index 031cf74..2e5d68d 100644
--- a/uart/uart.c
+++ b/uart/uart.c
@@ -1,5 +1,218 @@
+#include <cm4.h>
+#include <reg/gpio.h>
+#include <reg/port.h>
+#include <reg/sim.h>
+#include <reg/uart.h>
+#include <stddef.h>
+#include <stdarg.h>
+
 #include "uart.h"
+#include "../asm.h"
+
+enum {
+	SBR_VAL = 39,
+	BRFA_VAL = 2,
+	SRBSZ = 1024,
+	FIFOSZ = 8,
+};
+
+static struct {
+	unsigned char buf[SRBSZ];
+	int start, end;
+} send_rb = { .start = 0, .end = 0 };
+
+static inline size_t rb_store(void *_data, size_t size)
+{
+	unsigned char *data = _data;
+	size_t avail;
+	int start, end;
+
+	start = send_rb.start;
+	end = send_rb.end;
+	avail = (start + sizeof send_rb.buf - end) % sizeof send_rb.buf - 1;
+
+	if (size > avail)
+		size = avail;
+
+	for (int i = 0; i < size; i++)
+		send_rb.buf[(end + i) % sizeof send_rb.buf] = data[i];
+	send_rb.end = (end + size) % sizeof send_rb.buf;
+
+	/* Enable Transmission Interrupt */
+	CLI();
+	SET_BIT(UART0_C2, C2_TIE);
+	STI();
+
+	return size;
+}
 
 void uart_setup(void)
 {
+	/* Clock gating for UART0 */
+	SET_BIT(SIM_SCGC4, SCGC4_UART0);
+	/* Disable TX and RX */
+	SET_MASKED(UART0_C2, BV(C2_TE) | BV(C2_RE), 0);
+	/* Default settings */
+	UART0_C1 = 0;
+	/* SBR and BRFA for baud rate */
+	SET_MASKED(UART0_BDH, BDH_SBR_M, ((SBR_VAL & 0x1f00) >> 8) << BDH_SBR);
+	SET_MASKED(UART0_BDL, BDL_SBR_M, (SBR_VAL & 0xff) << BDL_SBR);
+	SET_MASKED(UART0_C4, C4_BRFA_M, BRFA_VAL << C4_BRFA);
+	/* flush and enable TX FIFO */
+	UART0_CFIFO |= BV(CFIFO_TXFLUSH);
+	UART0_PFIFO |= BV(PFIFO_TXFE);
+	/* set watermark at 1 entry */
+	SET_MASKED(UART0_TWFIFO, TWFIFO_TXWATER_M, 1 << TWFIFO_TXWATER);
+	/* NVIC enable interrupt */
+	ISR_CLRPEND(45);
+	INTPRI(45) = 0xf0;
+	ISR_SETENA(45);
+	/* enable correct ALT MUX on TX pin */
+	PORTB_PCR(17) = 3 << PCR_MUX;
+	/* enable TX */
+	SET_MASKED(UART0_C2, BV(C2_TE), BV(C2_TE));
+}
+
+void uart_putchar(int c)
+{
+	static unsigned char buf[128];
+	static size_t size = 0;
+
+	if (c == '\n')
+		uart_putchar('\r');
+
+	buf[size++] = c;
+
+	if (size >= sizeof buf || c == '\n') {
+		rb_store(buf, size);
+		size = 0;
+	}
+}
+
+void uart_puts(const char *s)
+{
+	for (size_t i = 0; s[i]; i++)
+		uart_putchar(s[i]);
+	uart_putchar('\n');
+}
+
+static inline void putul(unsigned long n, int base)
+{
+	static const char *digits = "0123456789abcdef";
+	int i;
+	char tmp[64];
+
+	if (base < 2 || base > 16)
+		return;
+
+	if (n == 0) {
+		uart_putchar('0');
+		return;
+	}
+	for (i = 0; n; i++) {
+		int res = n % base;
+		n = n / base;
+		tmp[i] = digits[res];
+	}
+
+	for (i -= 1; i >= 0; i--)
+		uart_putchar(tmp[i]);
+}
+
+static inline void putl(long n)
+{
+	int i;
+	char tmp[64];
+
+	if (n < 0) {
+		uart_putchar('-');
+		n *= -1;
+	}
+
+	if (n == 0) {
+		uart_putchar('0');
+		return;
+	}
+
+	for (i = 0; n; i++) {
+		int res = n % 10;
+		n = n / 10;
+		tmp[i] = '0' + res;
+	}
+
+	for (i -= 1; i >= 0; i--)
+		uart_putchar(tmp[i]);
+}
+
+void uart_printf(const char *fmt, ...)
+{
+	va_list ap;
+	const char *p;
+	int ival;
+	unsigned uival;
+	long lival;
+	unsigned long ulival;
+
+	va_start(ap, fmt);
+	for (p = fmt; *p; p++) {
+		if (*p != '%') {
+			uart_putchar(*p);
+			continue;
+		}
+		switch (*++p) {
+		case 'd': case 'i':
+			ival = va_arg(ap, int);
+			putl(ival);
+			break;
+		case 'o': case 'u': case 'x':
+			uival = va_arg(ap, unsigned);
+			switch (*p) {
+			case 'o': putul(uival, 8); break;
+			case 'u': putul(uival, 10); break;
+			case 'x': putul(uival, 16); break;
+			}
+			break;
+		case 'l':
+			switch (*++p) {
+			case 'd': case 'i':
+				lival = va_arg(ap, long);
+				putl(lival);
+				break;
+			case 'o': case 'u': case 'x':
+				ulival = va_arg(ap, unsigned long);
+				switch (*p) {
+				case 'o': putul(ulival, 8); break;
+				case 'u': putul(ulival, 10); break;
+				case 'x': putul(ulival, 16); break;
+				}
+				break;
+			}
+		}
+	}
+	va_end(ap);
+}
+
+void uart0_isr(void)
+{
+	int avail, start, end, tosend;
+
+	if (!GET_BIT(UART0_S1, S1_TDRE))
+		return;
+
+	avail = FIFOSZ - UART0_TCFIFO;
+	CLI();
+	start = send_rb.start;
+	end = send_rb.end;
+	tosend = (end + sizeof send_rb.buf - start) % sizeof send_rb.buf;
+	if (tosend == 0)
+		UNSET_BIT(UART0_C2, C2_TIE);
+	STI();
+
+	if (tosend > avail)
+		tosend = avail;
+
+	for (int i = 0; i < tosend; i++)
+		UART0_D = send_rb.buf[(start + i) % sizeof send_rb.buf];
+
+	send_rb.start = (start + tosend) % sizeof send_rb.buf;
 }
diff --git a/uart/uart.h b/uart/uart.h
index 984d704..2733bb7 100644
--- a/uart/uart.h
+++ b/uart/uart.h
@@ -2,5 +2,9 @@
 #define UART_UART_H
 
 void uart_setup(void);
+void uart_putchar(int c);
+void uart_printf(const char *fmt, ...);
+void uart_puts(const char *s);
+void uart0_isr(void);
 
 #endif /* UART_UART_H */