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

Manfred Huber
2013-03-27T04:50:17Z

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.

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.

If you don't want a patch for this bug please let me know. I will not
bother you again.

Best regards,
Manfred

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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