serial_mxc: disable new features of autobaud detection

Bit 7 of UCR3 is described in the i.MX3x/i.MX5x/i.MX6x
reference manuals as follows:

	Autobaud Detection Not Improved-. Disables new features of
	autobaud detection (See Baud Rate Automatic Detection
        Protocol, for more details).

	0 Autobaud detection new features selected
	1 Keep old autobaud detection mechanism

On at least i.MX6DQ, i.MX6DLS and i.MX53, the "new features"
occasionally cause the receiver to get out of sync and
continuously produce received characters of '\xff'.

This patch disables the "new feature" on all boards, since
there's no support for auto-baud in U-Boot on any of them.

More details are available in this post on i.MX Community:
	https://community.freescale.com/message/403254

Signed-off-by: Eric Nelson <eric.nelson@boundarydevices.com>
Tested-by: Fabio Estevam <fabio.estevam@freescale.com>
Acked-by: Stefano Babic <sbabic@denx.de>

diff --git a/drivers/serial/serial_mxc.c b/drivers/serial/serial_mxc.c
index 56bee55208e0acd0fced0ee0149a404786abc67a..313d560afce8635f3b1f29c3ea029173b69f8c40 100644 (file)
--- a/drivers/serial/serial_mxc.c
+++ b/drivers/serial/serial_mxc.c
@@ -77,7 +77,7 @@
 #define  UCR3_DSR        (1<<10) /* Data set ready */
 #define  UCR3_DCD        (1<<9)  /* Data carrier detect */
 #define  UCR3_RI         (1<<8)  /* Ring indicator */
-#define  UCR3_TIMEOUTEN  (1<<7)  /* Timeout interrupt enable */
+#define  UCR3_ADNIMP     (1<<7)  /* Autobaud Detection Not Improved */
 #define  UCR3_RXDSEN    (1<<6)  /* Receive status interrupt enable */
 #define  UCR3_AIRINTEN   (1<<5)  /* Async IR wake interrupt enable */
 #define  UCR3_AWAKEN    (1<<4)  /* Async wake interrupt enable */
@@ -186,7 +186,7 @@ static int mxc_serial_init(void)
 
        while (!(__REG(UART_PHYS + UCR2) & UCR2_SRST));
 
-       __REG(UART_PHYS + UCR3) = 0x0704;
+       __REG(UART_PHYS + UCR3) = 0x0704 | UCR3_ADNIMP;
        __REG(UART_PHYS + UCR4) = 0x8000;
        __REG(UART_PHYS + UESC) = 0x002b;
        __REG(UART_PHYS + UTIM) = 0x0;