[U-Boot] [PATCH 1/1 v3] omap3_beagle: Enabling UART3 first allows the Transmitter to be empty

[Tom Rini]

On Fri, Mar 29, 2013 at 10:43:34AM +0100, Albert ARIBAUD wrote:
> Hi Manfred,
> 
> On Fri, 29 Mar 2013 10:20:25 +0100, Manfred Huber <man.huber at arcor.de>
> wrote:
> 
> > On some OMAP3 devices when UART3 is configured for boot mode before SPL starts 
> > only THRE bit is set. We have to empty the transmitter before initialization 
> > starts. This patch avoids the use of CONFIG_SYS_NS16550_BROKEN_TEMT.
> > 
> > Signed-off-by: Manfred Huber <man.huber at arcor.de>
> > ---
> 
> Patch history is missing here.

That's largely because each iteration has been fairly different (we
started with adding CONFIG_SYS_NS16550_BROKEN_TEMPT to omap3_beagle).

> Also, I would like the commit summary (first commit message line, also
> subject of the patch mail) to clearly state what the patch *does* as
> opposed to what *happens*, because it is unclear right now if you're
> describing the solution or the issue. Something like :
> 
> "omap3_beagle: flush UART3 xmit on enable if TEMT is broken"

Agreed.

> 
> > README                     |    8 --------
> >  drivers/serial/ns16550.c   |   16 ++++++++++++++--
> >  include/configs/igep00x0.h |    3 ---
> >  3 files changed, 14 insertions(+), 13 deletions(-)
> > 
> > diff --git a/README b/README
> > index a336476..e6b3a50 100644
> > --- a/README
> > +++ b/README
> > @@ -616,14 +616,6 @@ The following options need to be configured:
> >  		boot loader that has already initialized the UART.  Define this
> >  		variable to flush the UART at init time.
> >  
> > -		CONFIG_SYS_NS16550_BROKEN_TEMT
> > -
> > -		16550 UART set the Transmitter Empty (TEMT) Bit when all output
> > -		has finished and the transmitter is totally empty. U-Boot waits
> > -		for this bit to be set to initialize the serial console. On some
> > -		broken platforms this bit is not set in SPL making U-Boot to
> > -		hang while waiting for TEMT. Define this option to avoid it.
> > -
> >  
> >  - Console Interface:
> >  		Depending on board, define exactly one serial port
> > 
> > diff --git a/drivers/serial/ns16550.c b/drivers/serial/ns16550.c
> > index 87a0917..2922a2c 100644
> > --- a/drivers/serial/ns16550.c
> > +++ b/drivers/serial/ns16550.c
> > @@ -36,10 +36,22 @@
> >  
> >  void NS16550_init(NS16550_t com_port, int baud_divisor)
> >  {
> > -#if (!defined(CONFIG_SYS_NS16550_BROKEN_TEMT))
> > +#if (defined(CONFIG_SPL_BUILD) && defined(CONFIG_OMAP34XX))
> > +	/* On some OMAP3 devices when UART3 is configured for boot mode before
> > +	   SPL starts only THRE bit is set. We have to empty the transmitter
> > +	   before initialization starts. */

/*
 * Multiline comments
 * must be like this.
 */

-- 
Tom
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