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

[Tom Rini]

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On 10/09/12 15:09, Stephen Warren wrote:
> 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.

Yes, if SPL wasn't previously clearing the BSS, this would be a
problem now.

- -- 
Tom
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