[U-Boot] [PATCH 5/5] tegra: Implement board_pre_console_panic() for Seaboard

[Simon Glass]

Hi Stephen,

On Mon, Mar 19, 2012 at 6:22 PM, Stephen Warren <swarren at wwwdotorg.org> wrote:
> On 03/19/2012 04:59 PM, Simon Glass wrote:
>> Hi Stephen,
>>
>> On Mon, Mar 19, 2012 at 2:18 PM, Stephen Warren <swarren at wwwdotorg.org> wrote:
>>> On 03/19/2012 02:27 PM, Simon Glass wrote:
>>>> We enable this feature on all UARTs for Seaboard. This ensures that a
>>>> message is printed if CONFIG_OF_CONTROL is in use and a value device tree
>>>> is not available.
>>>
>>> Why not just enabled this on UARTD, since that's what Seaboard uses?
>>>
>>> I guess some derivatives do use UARTB too, which makes things quite
>>> painful. Perhaps at least limit this to UARTB + UARTD, and not all the
>>> others?
>>
>> At the moment we can use Seaboard as a generic Tegra2 board, so we
>> want the widest possible select of UARTs. I think there is one board
>> that uses A?
>>
>> Really I would prefer that we explicitly create a generic Tegra2
>> board, once the fdt stuff is bedded in.
>
> Well, one of Wolfgang's main objections was blasting the panic message
> through all possible UARTs, which might send junk to something other
> than a debug UART (e.g. machinery and life support systems were
> mentioned). This change doesn't seem to solve that. For low-level debug
> like this, shouldn't we just route it to one single UART that the config
> file selects?

The objection was that we did it blindly without knowing what ports
were safe to use. Now it is under board control. In the case of a
board where we want the pre-console panic function but only want it on
UARTB we can do that by creating a board file and a config.

The CONFIG cannot select which UART to use, because we only have one
config for all the Seaboard variants, and some use different UARTs.
Only the device tree can tell you which is the console UART. There is
a bit of a conflict here, but keep in mind we are trying to have a
single U-Boot binary - anything that relies on a CONFIG will break
that.

>
> We can certainly think about refactoring things into a unified board
> file, but that seems like something unrelated to do later...

Yes it is. But we use Seaboard as our base board for all the Tegra2
board variants. Some use UARTA, C and one uses D. UART D is a pain
because it is shared with SPI.

So my preference is to leave it as it is, but if you just want it to
be D, then we can go with that for now. At least now it is only a
single line change. Let me know.

Regards,
Simon