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>

1 files changed, 12 insertions, 5 deletions

diff --git a/drivers/serial/8250.c b/drivers/serial/8250.c
index 3bbf0cc6e53f..30e8beb71430 100644
--- a/drivers/serial/8250.c
+++ b/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;