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

[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@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

-- 
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
...when fits of creativity run strong, more than  one  programmer  or
writer  has  been  known to abandon the desktop for the more spacious
floor.                                             - Fred Brooks, Jr.

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

[Dirk Behme]

Wolfgang Denk wrote:
> 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@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.

How do you test this? Whats your test case? Then I will try to test it 
on a OMAP5912 OSK.

Thanks

Dirk

> 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)

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

[Wolfgang Denk]

Hello Dirk,

in message <47740D48.1090803@googlemail.com> you wrote:
>
> >  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.
> 
> How do you test this? Whats your test case? Then I will try to test it 
> on a OMAP5912 OSK.

Forgot to mention that it's been tested on the OMAP5912 devel kit and
a custom board, too.

The real test is some custom application which is not available to the
public.

For now, it would be helpful to receive confirmation that it does not
break any existing board support.

Best regards,

Wolfgang Denk

-- 
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
"The two most common things in the universe are hydrogen  and  stupi-
dity."

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

[Wolfgang Denk]

In message <20071227095654.717B62405E@gemini.denx.de> you wrote:
> 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@denx.de>

Applied.

Best regards,

Wolfgang Denk

-- 
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
"It is better to have tried and failed than to have  failed  to  try,
but the result's the same."                           - Mike Dennison