[PATCH] Serial: Convert 8250 revision-based bug fixes to bug bitmask

For some 8250 port types, we used to check the type of the port, and
then determine whether the chip revision means the device is buggy.
Instead, introduce a bit array, and set the appropriate bit(s) when
we discover a buggy device.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

drivers/serial/8250.c

@@ -132,9 +132,9 @@ struct uart_8250_port {
 	struct uart_port	port;
 	struct timer_list	timer;		/* "no irq" timer */
 	struct list_head	list;		/* ports on this IRQ */
-	unsigned int		capabilities;	/* port capabilities */
+	unsigned short		capabilities;	/* port capabilities */
+	unsigned short		bugs;		/* port bugs */
 	unsigned int		tx_loadsz;	/* transmit fifo load size */
-	unsigned short		rev;
 	unsigned char		acr;
 	unsigned char		ier;
 	unsigned char		lcr;
@@ -560,7 +560,14 @@ static void autoconfig_has_efr(struct uart_8250_port *up)
 	if (id1 == 0x16 && id2 == 0xC9 &&
 	    (id3 == 0x50 || id3 == 0x52 || id3 == 0x54)) {
 		up->port.type = PORT_16C950;
-		up->rev = rev | (id3 << 8);
+
+		/*
+		 * Enable work around for the Oxford Semiconductor 952 rev B
+		 * chip which causes it to seriously miscalculate baud rates
+		 * when DLL is 0.
+		 */
+		if (id3 == 0x52 && rev == 0x01)
+			up->bugs |= UART_BUG_QUOT;
 		return;
 	}
 
@@ -577,8 +584,6 @@ static void autoconfig_has_efr(struct uart_8250_port *up)
 
 	id2 = id1 >> 8;
 	if (id2 == 0x10 || id2 == 0x12 || id2 == 0x14) {
-		if (id2 == 0x10)
-			up->rev = id1 & 255;
 		up->port.type = PORT_16850;
 		return;
 	}
@@ -809,6 +814,7 @@ static void autoconfig(struct uart_8250_port *up, unsigned int probeflags)
 //	save_flags(flags); cli();
 
 	up->capabilities = 0;
+	up->bugs = 0;
 
 	if (!(up->port.flags & UPF_BUGGY_UART)) {
 		/*
@@ -1677,12 +1683,9 @@ serial8250_set_termios(struct uart_port *port, struct termios *termios,
 	quot = serial8250_get_divisor(port, baud);
 
 	/*
-	 * Work around a bug in the Oxford Semiconductor 952 rev B
-	 * chip which causes it to seriously miscalculate baud rates
-	 * when DLL is 0.
+	 * Oxford Semi 952 rev B workaround
 	 */
-	if ((quot & 0xff) == 0 && up->port.type == PORT_16C950 &&
-	    up->rev == 0x5201)
+	if (up->bugs & UART_BUG_QUOT && (quot & 0xff) == 0)
 		quot ++;
 
 	if (up->capabilities & UART_CAP_FIFO && up->port.fifosize > 1) {

drivers/serial/8250.h

@@ -51,6 +51,8 @@ struct serial8250_config {
 #define UART_CAP_AFE	(1 << 11)	/* MCR-based hw flow control */
 #define UART_CAP_UUE	(1 << 12)	/* UART needs IER bit 6 set (Xscale) */
 
+#define UART_BUG_QUOT	(1 << 0)	/* UART has buggy quot LSB */
+
 #if defined(__i386__) && (defined(CONFIG_M386) || defined(CONFIG_M486))
 #define _INLINE_ inline
 #else