openwrt/target/linux/ixp4xx/patches-4.9/160-delayed_uart_io.patch

--- a/drivers/tty/serial/8250/8250_core.c
+++ b/drivers/tty/serial/8250/8250_core.c
@@ -833,6 +833,7 @@ static int serial8250_probe(struct platf
 		uart.port.get_mctrl	= p->get_mctrl;
 		uart.port.pm		= p->pm;
 		uart.port.dev		= &dev->dev;
+		uart.port.rw_delay	= p->rw_delay;
 		uart.port.irqflags	|= irqflag;
 		ret = serial8250_register_8250_port(&uart);
 		if (ret < 0) {
@@ -989,6 +990,7 @@ int serial8250_register_8250_port(struct
 		uart->bugs		= up->bugs;
 		uart->port.mapbase      = up->port.mapbase;
 		uart->port.mapsize      = up->port.mapsize;
+		uart->port.rw_delay	= up->port.rw_delay;
 		uart->port.private_data = up->port.private_data;
 		uart->tx_loadsz		= up->tx_loadsz;
 		uart->capabilities	= up->capabilities;
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -2233,6 +2233,7 @@ uart_report_port(struct uart_driver *drv
 		snprintf(address, sizeof(address),
 			 "I/O 0x%lx offset 0x%x", port->iobase, port->hub6);
 		break;
+	case UPIO_MEM_DELAY:
 	case UPIO_MEM:
 	case UPIO_MEM16:
 	case UPIO_MEM32:
@@ -2897,6 +2898,7 @@ int uart_match_port(struct uart_port *po
 	case UPIO_HUB6:
 		return (port1->iobase == port2->iobase) &&
 		       (port1->hub6   == port2->hub6);
+	case UPIO_MEM_DELAY:
 	case UPIO_MEM:
 	case UPIO_MEM16:
 	case UPIO_MEM32:
--- a/include/linux/serial_8250.h
+++ b/include/linux/serial_8250.h
@@ -28,6 +28,7 @@ struct plat_serial8250_port {
 	void            *private_data;
 	unsigned char	regshift;	/* register shift */
 	unsigned char	iotype;		/* UPIO_* */
+	unsigned int rw_delay;	/* udelay for slower busses IXP4XX Expansion Bus */
 	unsigned char	hub6;
 	upf_t		flags;		/* UPF_* flags */
 	unsigned int	type;		/* If UPF_FIXED_TYPE */
--- a/include/linux/serial_core.h
+++ b/include/linux/serial_core.h
@@ -152,6 +152,7 @@ struct uart_port {
 #define UPIO_TSI		(SERIAL_IO_TSI)		/* Tsi108/109 type IO */
 #define UPIO_MEM32BE		(SERIAL_IO_MEM32BE)	/* 32b big endian */
 #define UPIO_MEM16		(SERIAL_IO_MEM16)	/* 16b little endian */
+#define UPIO_MEM_DELAY		(SERIAL_IO_MEM_DELAY)
 
 	unsigned int		read_status_mask;	/* driver specific */
 	unsigned int		ignore_status_mask;	/* driver specific */
@@ -233,6 +234,7 @@ struct uart_port {
 	int			hw_stopped;		/* sw-assisted CTS flow state */
 	unsigned int		mctrl;			/* current modem ctrl settings */
 	unsigned int		timeout;		/* character-based timeout */
+	unsigned int		rw_delay;		/* udelay for slow busses, IXP4XX Expansion Bus */
 	unsigned int		type;			/* port type */
 	const struct uart_ops	*ops;
 	unsigned int		custom_divisor;
--- a/drivers/tty/serial/8250/8250_port.c
+++ b/drivers/tty/serial/8250/8250_port.c
@@ -384,6 +384,20 @@ static unsigned int mem16_serial_in(stru
 	return readw(p->membase + offset);
 }
 
+static unsigned int memdelay_serial_in(struct uart_port *p, int offset)
+{
+	struct uart_8250_port *up = (struct uart_8250_port *)p;
+	udelay(up->port.rw_delay);
+	return mem_serial_in(p, offset);
+}
+
+static void memdelay_serial_out(struct uart_port *p, int offset, int value)
+{
+	struct uart_8250_port *up = (struct uart_8250_port *)p;
+	udelay(up->port.rw_delay);
+	mem_serial_out(p, offset, value);
+}
+
 static void mem32_serial_out(struct uart_port *p, int offset, int value)
 {
 	offset = offset << p->regshift;
@@ -456,6 +470,11 @@ static void set_io_from_upio(struct uart
 		p->serial_out = mem32be_serial_out;
 		break;
 
+	case UPIO_MEM_DELAY:
+		p->serial_in = memdelay_serial_in;
+		p->serial_out = memdelay_serial_out;
+		break;
+
 #ifdef CONFIG_SERIAL_8250_RT288X
 	case UPIO_AU:
 		p->serial_in = au_serial_in;
@@ -483,6 +502,7 @@ serial_port_out_sync(struct uart_port *p
 	case UPIO_MEM16:
 	case UPIO_MEM32:
 	case UPIO_MEM32BE:
+	case UPIO_MEM_DELAY:
 	case UPIO_AU:
 		p->serial_out(p, offset, value);
 		p->serial_in(p, UART_LCR);	/* safe, no side-effects */
@@ -2759,6 +2779,7 @@ static int serial8250_request_std_resour
 	case UPIO_MEM32BE:
 	case UPIO_MEM16:
 	case UPIO_MEM:
+	case UPIO_MEM_DELAY:
 		if (!port->mapbase)
 			break;
 
@@ -2797,6 +2818,7 @@ static void serial8250_release_std_resou
 	case UPIO_MEM32BE:
 	case UPIO_MEM16:
 	case UPIO_MEM:
+	case UPIO_MEM_DELAY:
 		if (!port->mapbase)
 			break;
 
--- a/include/uapi/linux/serial.h
+++ b/include/uapi/linux/serial.h
@@ -70,6 +70,7 @@ struct serial_struct {
 #define SERIAL_IO_TSI	  5
 #define SERIAL_IO_MEM32BE 6
 #define SERIAL_IO_MEM16	7
+#define SERIAL_IO_MEM_DELAY 10
 
 #define UART_CLEAR_FIFO		0x01
 #define UART_USE_FIFO		0x02