[serial] Add general abstraction of a 16550-compatible UART

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/include/ipxe/errfile.h

@@ -89,6 +89,7 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
 #define ERRFILE_i2c_bit		     ( ERRFILE_DRIVER | 0x00120000 )
 #define ERRFILE_spi_bit		     ( ERRFILE_DRIVER | 0x00130000 )
 #define ERRFILE_nvsvpd		     ( ERRFILE_DRIVER | 0x00140000 )
+#define ERRFILE_uart		     ( ERRFILE_DRIVER | 0x00150000 )
 
 #define ERRFILE_3c509		     ( ERRFILE_DRIVER | 0x00200000 )
 #define ERRFILE_bnx2		     ( ERRFILE_DRIVER | 0x00210000 )

src/include/ipxe/uart.h

@@ -0,0 +1,131 @@
+#ifndef _IPXE_UART_H
+#define _IPXE_UART_H
+
+/** @file
+ *
+ * 16550-compatible UART
+ *
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
+
+#include <stdint.h>
+
+/** Transmitter holding register */
+#define UART_THR 0x00
+
+/** Receiver buffer register */
+#define UART_RBR 0x00
+
+/** Interrupt enable register */
+#define UART_IER 0x01
+
+/** FIFO control register */
+#define UART_FCR 0x02
+#define UART_FCR_FE	0x01	/**< FIFO enable */
+
+/** Line control register */
+#define UART_LCR 0x03
+#define UART_LCR_WLS0	0x01	/**< Word length select bit 0 */
+#define UART_LCR_WLS1	0x02	/**< Word length select bit 1 */
+#define UART_LCR_STB	0x04	/**< Number of stop bits */
+#define UART_LCR_PEN	0x08	/**< Parity enable */
+#define UART_LCR_EPS	0x10	/**< Even parity select */
+#define UART_LCR_DLAB	0x80	/**< Divisor latch access bit */
+
+#define UART_LCR_WORD_LEN(x)	( ( (x) - 5 ) << 0 )	/**< Word length */
+#define UART_LCR_STOP_BITS(x)	( ( (x) - 1 ) << 2 )	/**< Stop bits */
+#define UART_LCR_PARITY(x)	( ( (x) - 0 ) << 3 )	/**< Parity */
+
+/**
+ * Calculate line control register value
+ *
+ * @v word_len		Word length (5-8)
+ * @v parity		Parity (0=none, 1=odd, 3=even)
+ * @v stop_bits		Stop bits (1-2)
+ * @ret lcr		Line control register value
+ */
+#define UART_LCR_WPS( word_len, parity, stop_bits )	\
+	( UART_LCR_WORD_LEN ( (word_len) ) |		\
+	  UART_LCR_PARITY ( (parity) ) |		\
+	  UART_LCR_STOP_BITS ( (stop_bits) ) )
+
+/** Default LCR value: 8 data bits, no parity, one stop bit */
+#define UART_LCR_8N1 UART_LCR_WPS ( 8, 0, 1 )
+
+/** Modem control register */
+#define UART_MCR 0x04
+#define UART_MCR_DTR	0x01	/**< Data terminal ready */
+#define UART_MCR_RTS	0x02	/**< Request to send */
+
+/** Line status register */
+#define UART_LSR 0x05
+#define UART_LSR_DR	0x01	/**< Data ready */
+#define UART_LSR_THRE	0x20	/**< Transmitter holding register empty */
+#define UART_LSR_TEMT	0x40	/**< Transmitter empty */
+
+/** Scratch register */
+#define UART_SCR 0x07
+
+/** Divisor latch (least significant byte) */
+#define UART_DLL 0x00
+
+/** Divisor latch (most significant byte) */
+#define UART_DLM 0x01
+
+/** Maximum baud rate */
+#define UART_MAX_BAUD 115200
+
+/** A 16550-compatible UART */
+struct uart {
+	/** I/O port base address */
+	void *base;
+	/** Baud rate divisor */
+	uint16_t divisor;
+	/** Line control register */
+	uint8_t lcr;
+};
+
+/** Symbolic names for port indexes */
+enum uart_port {
+	COM1 = 1,
+	COM2 = 2,
+	COM3 = 3,
+	COM4 = 4,
+};
+
+#include <bits/uart.h>
+
+void uart_write ( struct uart *uart, unsigned int addr, uint8_t data );
+uint8_t uart_read ( struct uart *uart, unsigned int addr );
+int uart_select ( struct uart *uart, unsigned int port );
+
+/**
+ * Check if received data is ready
+ *
+ * @v uart		UART
+ * @ret ready		Data is ready
+ */
+static inline int uart_data_ready ( struct uart *uart ) {
+	uint8_t lsr;
+
+	lsr = uart_read ( uart, UART_LSR );
+	return ( lsr & UART_LSR_DR );
+}
+
+/**
+ * Receive data
+ *
+ * @v uart		UART
+ * @ret data		Data
+ */
+static inline uint8_t uart_receive ( struct uart *uart ) {
+
+	return uart_read ( uart, UART_RBR );
+}
+
+extern void uart_transmit ( struct uart *uart, uint8_t data );
+extern void uart_flush ( struct uart *uart );
+extern int uart_init ( struct uart *uart, unsigned int baud, uint8_t lcr );
+
+#endif /* _IPXE_UART_H */