When we detect that a 16550 was in fact part of a NatSemi SuperIO chip

with high-speed mode enabled, we switch it to high-speed mode so that
baud_base becomes 921600. However, we also need to multiply the baud
divisor by 8 at the same time, in case it's already in use as a console.

Signed-off-by: David Woodhouse
Acked-by: Tom Rini
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

drivers/serial/8250.c

@@ -682,8 +682,6 @@ static void autoconfig_16550a(struct uart_8250_port *up)
 	 * from EXCR1. Switch back to bank 0, change it in MCR. Then
 	 * switch back to bank 2, read it from EXCR1 again and check
 	 * it's changed. If so, set baud_base in EXCR2 to 921600. -- dwmw2
-	 * On PowerPC we don't want to change baud_base, as we have
-	 * a number of different divisors.  -- Tom Rini
 	 */
 	serial_outp(up, UART_LCR, 0);
 	status1 = serial_in(up, UART_MCR);
@@ -699,16 +697,25 @@ static void autoconfig_16550a(struct uart_8250_port *up)
 		serial_outp(up, UART_MCR, status1);
 
 		if ((status2 ^ status1) & UART_MCR_LOOP) {
-#ifndef CONFIG_PPC
+			unsigned short quot;
+
 			serial_outp(up, UART_LCR, 0xE0);
+
+			quot = serial_inp(up, UART_DLM) << 8;
+			quot += serial_inp(up, UART_DLL);
+			quot <<= 3;
+
 			status1 = serial_in(up, 0x04); /* EXCR1 */
 			status1 &= ~0xB0; /* Disable LOCK, mask out PRESL[01] */
 			status1 |= 0x10;  /* 1.625 divisor for baud_base --> 921600 */
 			serial_outp(up, 0x04, status1);
+
+			serial_outp(up, UART_DLL, quot & 0xff);
+			serial_outp(up, UART_DLM, quot >> 8);
+
 			serial_outp(up, UART_LCR, 0);
-			up->port.uartclk = 921600*16;
-#endif
 
+			up->port.uartclk = 921600*16;
 			up->port.type = PORT_NS16550A;
 			up->capabilities |= UART_NATSEMI;
 			return;