[U-Boot-Users] [PATCH] OMAP5912: fix FIFO handling in UART driver

[Wolfgang Denk]

According to the OMAP5912 Serial Interfaces Reference Guide (see
http://focus.ti.com/lit/ug/spru760c/spru760c.pdf, page 150), the
FIFO_EN enable bit in the FIFO Control Register (FCR) can only be
changed when the baud clock is not running, i. e. when both DLL and
DLH are set to 0.

Thus make sure that DLL and DLH are 0 when writing the FCR.

Signed-off-by: Wolfgang Denk <wd at denx.de>
---
 drivers/serial/ns16550.c |   16 ++++++++++++----
 1 files changed, 12 insertions(+), 4 deletions(-)

Unfortunately I can test this only on a limited number of boards with
other NS16550 compatible UARTs (like TQM85xx, TQM83xx); the patch
seems to cause no problems there.

Comments welcome...


diff --git a/drivers/serial/ns16550.c b/drivers/serial/ns16550.c
index 2429464..6b3f60e 100644
--- a/drivers/serial/ns16550.c
+++ b/drivers/serial/ns16550.c
@@ -21,11 +21,15 @@ void NS16550_init (NS16550_t com_port, int baud_divisor)
 	com_port->mdr1 = 0x7;	/* mode select reset TL16C750*/
 #endif
 	com_port->lcr = LCR_BKSE | LCRVAL;
-	com_port->dll = baud_divisor & 0xff;
-	com_port->dlm = (baud_divisor >> 8) & 0xff;
+	com_port->dll = 0;
+	com_port->dlm = 0;
 	com_port->lcr = LCRVAL;
 	com_port->mcr = MCRVAL;
 	com_port->fcr = FCRVAL;
+	com_port->lcr = LCR_BKSE | LCRVAL;
+	com_port->dll = baud_divisor & 0xff;
+	com_port->dlm = (baud_divisor >> 8) & 0xff;
+	com_port->lcr = LCRVAL;
 #if defined(CONFIG_OMAP)
 #if defined(CONFIG_APTIX)
 	com_port->mdr1 = 3;	/* /13 mode so Aptix 6MHz can hit 115200 */
@@ -38,12 +42,16 @@ void NS16550_init (NS16550_t com_port, int baud_divisor)
 void NS16550_reinit (NS16550_t com_port, int baud_divisor)
 {
 	com_port->ier = 0x00;
+	com_port->lcr = LCR_BKSE | LCRVAL;
+	com_port->dll = 0;
+	com_port->dlm = 0;
+	com_port->lcr = LCRVAL;
+	com_port->mcr = MCRVAL;
+	com_port->fcr = FCRVAL;
 	com_port->lcr = LCR_BKSE;
 	com_port->dll = baud_divisor & 0xff;
 	com_port->dlm = (baud_divisor >> 8) & 0xff;
 	com_port->lcr = LCRVAL;
-	com_port->mcr = MCRVAL;
-	com_port->fcr = FCRVAL;
 }
 
 void NS16550_putc (NS16550_t com_port, char c)
-- 
1.5.2.2


Best regards,

Wolfgang Denk

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DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
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