[U-Boot] [PATCH 1/1 v2] omap3_beagle: Enabling UART3 first allows the Transmitter to be empty

[Manfred Huber <man.huber@arcor.de>]

On 2013-03-27 10:29, Javier Martinez Canillas wrote:
> On Wed, Mar 27, 2013 at 5:50 AM, Manfred Huber <man.huber@arcor.de> wrote:
>> Please test the Patch. It is very simple on a Beagleboard. I guess you
>> have flashed the actual SPL and u-boot and Beagleboard boots correctly.
>> Now press and hold 'User' button and connect power. SPL should hang.
>> You can see some symbols on the console from the ROM code.
>>
>
> Hi Manfred,
>
> I don't have access to my IGEP board right now but I'll test your
> patch as soon as posible.
>
>> Install the Patch, compile it and flash the NAND. Beagleboard still
>> boots correctly. Now press and hold 'User' button again and Beagleboard
>> should also boot correctly. The Patch works.
>>
>> I suspect the IGEP board has the same bug. If so, the Patch should work
>> on this board too and we don't need CONFIG_SYS_NS16550_BROKEN_TEMT
>> anymore.
>>
>
> I still think that we should keep CONFIG_SYS_NS16550_BROKEN_TEMT or
> something similar instead of just checking for CONFIG_OMAP34XX. Since
> we don't know if this problem is also present on other TI OMAP
> platforms (or any other platform). I would just change
> CONFIG_SYS_NS16550_BROKEN_TEMT semantics once is confirmed that this
> also fixes the issue on IGEP boards.
>
> Also, if you are removing CONFIG_SYS_NS16550_BROKEN_TEMT then you have
> to update the README too since it is explained there what this config
> option does.
>
>> If you don't want a patch for this bug please let me know. I will not
>> bother you again.
>>
>
> Thanks a lot for working on this. Some people work on mainline U-Boot
> on their free time (like myself) so it can take a few days until you
> get a response about a patch. Please be patient :-)
>

Hi Javier,

Also like me. The patch is not for me, because I have written my own 
serial driver. So this comment was only not to waste your and my time if 
no one needs this patch.

Best regards,
Manfred

>> Best regards,
>> Manfred
>>
>>
>
> Thank a lot and best regards,
> Javier
>
>>
>> On 2013-03-25 23:02, Manfred Huber wrote:
>>>
>>> From: Manfred Huber
>>>
>>> Due to a Bug in the ROM code of some OMAP3 devices, the TEMT bit is not
>>> set if UART3 is configured before (only THRE is set). Reason is the
>>> disabling of UART3 even though the Transmitter is not empty. Enabling
>>> UART3 allows the Transmitter to be empty.
>>>
>>> Signed-off-by: Manfred Huber <man.huber@arcor.de>
>>> ---
>>>    drivers/serial/ns16550.c |   12 ++++++++++--
>>>    1 file changed, 10 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/serial/ns16550.c b/drivers/serial/ns16550.c
>>> index b2da8b3..24ff84f 100644
>>> --- a/drivers/serial/ns16550.c
>>> +++ b/drivers/serial/ns16550.c
>>> @@ -36,10 +36,18 @@
>>>
>>>    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))
>>> +    if ((serial_in(&com_port->lsr) & (UART_LSR_TEMT | UART_LSR_THRE))
>>> == UART_LSR_THRE) {
>>> +        serial_out(UART_LCR_DLAB, &com_port->lcr);
>>> +        serial_out(baud_divisor & 0xff, &com_port->dll);
>>> +        serial_out((baud_divisor >> 8) & 0xff, &com_port->dlm);
>>> +        serial_out(UART_LCRVAL, &com_port->lcr);
>>> +        serial_out(0, &com_port->mdr1);
>>> +    }
>>> +#endif
>>> +
>>>        while (!(serial_in(&com_port->lsr) & UART_LSR_TEMT))
>>>            ;
>>> -#endif
>>>
>>>        serial_out(CONFIG_SYS_NS16550_IER, &com_port->ier);
>>>    #if (defined(CONFIG_OMAP) && !defined(CONFIG_OMAP3_ZOOM2)) || \
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>>
>>