serial: 8250-mtk: add follow control

Add SW and HW follow control function.
Signed-off-by: Long Cheng <long.cheng@mediatek.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/8250/8250_mtk.c

@@ -21,12 +21,14 @@
 
 #include "8250.h"
 
-#define UART_MTK_HIGHS		0x09	/* Highspeed register */
-#define UART_MTK_SAMPLE_COUNT	0x0a	/* Sample count register */
-#define UART_MTK_SAMPLE_POINT	0x0b	/* Sample point register */
+#define MTK_UART_HIGHS		0x09	/* Highspeed register */
+#define MTK_UART_SAMPLE_COUNT	0x0a	/* Sample count register */
+#define MTK_UART_SAMPLE_POINT	0x0b	/* Sample point register */
 #define MTK_UART_RATE_FIX	0x0d	/* UART Rate Fix Register */
-
 #define MTK_UART_DMA_EN		0x13	/* DMA Enable register */
+#define MTK_UART_RXTRI_AD	0x14	/* RX Trigger address */
+#define MTK_UART_FRACDIV_L	0x15	/* Fractional divider LSB address */
+#define MTK_UART_FRACDIV_M	0x16	/* Fractional divider MSB address */
 #define MTK_UART_DMA_EN_TX	0x2
 #define MTK_UART_DMA_EN_RX	0x5
 
@@ -46,6 +48,7 @@ enum dma_rx_status {
 struct mtk8250_data {
 	int			line;
 	unsigned int		rx_pos;
+	unsigned int		clk_count;
 	struct clk		*uart_clk;
 	struct clk		*bus_clk;
 	struct uart_8250_dma	*dma;
@@ -196,9 +199,15 @@ static void
 mtk8250_set_termios(struct uart_port *port, struct ktermios *termios,
 			struct ktermios *old)
 {
+	unsigned short fraction_L_mapping[] = {
+		0, 1, 0x5, 0x15, 0x55, 0x57, 0x57, 0x77, 0x7F, 0xFF, 0xFF
+	};
+	unsigned short fraction_M_mapping[] = {
+		0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 3
+	};
 	struct uart_8250_port *up = up_to_u8250p(port);
+	unsigned int baud, quot, fraction;
 	unsigned long flags;
-	unsigned int baud, quot;
 
 #ifdef CONFIG_SERIAL_8250_DMA
 	if (up->dma) {
@@ -214,7 +223,7 @@ mtk8250_set_termios(struct uart_port *port, struct ktermios *termios,
 	serial8250_do_set_termios(port, termios, old);
 
 	/*
-	 * Mediatek UARTs use an extra highspeed register (UART_MTK_HIGHS)
+	 * Mediatek UARTs use an extra highspeed register (MTK_UART_HIGHS)
 	 *
 	 * We need to recalcualte the quot register, as the claculation depends
 	 * on the vaule in the highspeed register.
@@ -230,18 +239,11 @@ mtk8250_set_termios(struct uart_port *port, struct ktermios *termios,
 				  port->uartclk / 16 / UART_DIV_MAX,
 				  port->uartclk);
 
-	if (baud <= 115200) {
-		serial_port_out(port, UART_MTK_HIGHS, 0x0);
+	if (baud < 115200) {
+		serial_port_out(port, MTK_UART_HIGHS, 0x0);
 		quot = uart_get_divisor(port, baud);
-	} else if (baud <= 576000) {
-		serial_port_out(port, UART_MTK_HIGHS, 0x2);
-
-		/* Set to next lower baudrate supported */
-		if ((baud == 500000) || (baud == 576000))
-			baud = 460800;
-		quot = DIV_ROUND_UP(port->uartclk, 4 * baud);
 	} else {
-		serial_port_out(port, UART_MTK_HIGHS, 0x3);
+		serial_port_out(port, MTK_UART_HIGHS, 0x3);
 		quot = DIV_ROUND_UP(port->uartclk, 256 * baud);
 	}
 
@@ -258,17 +260,29 @@ mtk8250_set_termios(struct uart_port *port, struct ktermios *termios,
 	/* reset DLAB */
 	serial_port_out(port, UART_LCR, up->lcr);
 
-	if (baud > 460800) {
+	if (baud >= 115200) {
 		unsigned int tmp;
 
-		tmp = DIV_ROUND_CLOSEST(port->uartclk, quot * baud);
-		serial_port_out(port, UART_MTK_SAMPLE_COUNT, tmp - 1);
-		serial_port_out(port, UART_MTK_SAMPLE_POINT,
-					(tmp - 2) >> 1);
+		tmp = (port->uartclk / (baud *  quot)) - 1;
+		serial_port_out(port, MTK_UART_SAMPLE_COUNT, tmp);
+		serial_port_out(port, MTK_UART_SAMPLE_POINT,
+					(tmp >> 1) - 1);
+
+		/*count fraction to set fractoin register */
+		fraction = ((port->uartclk  * 100) / baud / quot) % 100;
+		fraction = DIV_ROUND_CLOSEST(fraction, 10);
+		serial_port_out(port, MTK_UART_FRACDIV_L,
+						fraction_L_mapping[fraction]);
+		serial_port_out(port, MTK_UART_FRACDIV_M,
+						fraction_M_mapping[fraction]);
 	} else {
-		serial_port_out(port, UART_MTK_SAMPLE_COUNT, 0x00);
-		serial_port_out(port, UART_MTK_SAMPLE_POINT, 0xff);
+		serial_port_out(port, MTK_UART_SAMPLE_COUNT, 0x00);
+		serial_port_out(port, MTK_UART_SAMPLE_POINT, 0xff);
+		serial_port_out(port, MTK_UART_FRACDIV_L, 0x00);
+		serial_port_out(port, MTK_UART_FRACDIV_M, 0x00);
 	}
+	if (uart_console(port))
+		up->port.cons->cflag = termios->c_cflag;
 
 	spin_unlock_irqrestore(&port->lock, flags);
 	/* Don't rewrite B0 */