[U-Boot] [PATCH 67/72] serial: Unconditionally enable CONFIG_SERIAL_MULTI

[Stephen Warren]

On 10/09/2012 03:38 PM, Tom Rini wrote:
> On Tue, Oct 09, 2012 at 02:33:51PM -0600, Stephen Warren wrote:
>> On 09/29/2012 03:53 PM, Marek Vasut wrote:
>>> Enable CONFIG_SERIAL_MULTI for all builds of U-Boot. That
>>> includes both SPL builds and non-SPL builds, everything. To
>>> avoid poluting this patch with removal of ifdef-endif
>>> constructions containing CONFIG_SERIAL_MULTI, the
>>> CONFIG_SERIAL_MULTI is temporarily added into CPPFLAGS in
>>> config.mk . This will be again removed in following patch.
>> 
>> Marek,
>> 
>> This patch (at least, the version of it checked into u-boot/next)
>> breaks U-Boot on Tegra.
>> 
>> I believe the reason is because nothing ever calls
>> serial_initialize() in the SPL on Tegra. If I edit
>> arch/arm/cpu/arm720t/tegra20/spl.c function
>> preloader_console_init() to call serial_initialize() right before
>> it calls serial_init(), then everything works fine. Without
>> this, drivers/serial/serial.c is never initialised (not even BSS
>> cleared!) and so it's left set to some bogus value, and so
>> get_current() doesn't replace it with default_serial_console(),
>> so an invalid pointer is accessed, causing a hang or crash.
>> 
>> I'm not sure quite what the correct solution is here. Is Tegra's
>> custom spl.c doing too much; stuff that should come from the
>> common spl.c is cut/paste here? Or, is adding the call to
>> serial_initialize() the correct fix? Or, is the root-cause of the
>> problem that BSS (serial_current) isn't being cleared to 0?
> 
> Tegra SPL needs to either be updated ala common/spl/ 
> (preloader_console_init() calls serial_init()) or switched over to 
> it.

Hmm, well it's already calling serial_init() just not
serial_initialize(). Perhaps the issue is the following code missing
from Tegra's SPL:

	/* Clear the BSS. */
	memset(__bss_start, 0, __bss_end__ - __bss_start);

Anyway, I'll let Allen take a look at it, since he's most familiar
with Tegra SPL.