[U-Boot] SPL size issues on OMAP4

[Michael Cashwell]

On Jul 11, 2013, at 1:29 PM, Tom Rini <trini at ti.com> wrote:

> On Thu, Jul 11, 2013 at 01:01:30PM -0400, Michael Cashwell wrote:
>> I've been absent for a while and couldn't find a way to search the
>> list archives so I apologize if this has already been discussed?
>> 
>> I've been fighting the SPL binary growing too large on OMAP4 (using
>> custom configs and features). It's annoying that too large just fails
>> to run with no build or runtime notice. But that's a different issue.
> 
> What version are you using?  When SPL is too large a build-time failure
> is expected.

I've seen that happen in gross cases where it exceeds the 38K limit in 
omap4_common.h's CONFIG_SPL_MAX_SIZE but I currently have two configs
that are both well below that size yet the larger one doesn't run.

The larger MLO is 0x8a21 bytes (0x8c29 with the GP header) and _end is
0x4030cd74. This loops endlessly at 0x30080. I get no console output.
Even if the additional code is buggy it's not called early enough to
prevent at least the banner from going out so I'm pretty sure it's the
ROM not even starting it.

The smaller MLO is 0x757c bytes (0x7784 with the GP header) and _end is
0x4030b8cc. This runs OK.

I am still exploring.

> This is http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54303 which seems to
> have gotten little attention after initial triage.  I guess I need to
> find a little time to show it's still there.

Yes, I'd seen that. What I don't understand is why gcc doesn't just put
such strings into different sections like it does with its own __func__
strings. Then it would all just work.

I also don't get them implementing anonymous string merging while ignoring
GC. Both are size optimizations and the one they don't seem to care about
I'd expect to produce more savings.

>> Is there a work around I haven't thought of? I'm thinking along the
>> lines of disabling all printfs in SPL in the hope that will take the
>> strings away (since many are some sort of debug / progress message).
> 
> One option would be to add a "disable all output" option to SPL that
> would get all of the strings dropped.  I'm not sure how cleanly this can
> be done, but I know it has been done.

I have a pile of WIP to submit (a tiny one went today). I'm loath to
do anything major that would be unlikely to be accepted upstream because
of the work to keep it clean when I pull.

I'm thinking about a config option for SPL that would define away all
printf() and puts() calls. That would cover most of the low-hanging fruit.
It's not a complete solution and would mean no console output in SPL but
I'd think it could be done with a small source impact. Still noodling.

> Another option would be to do some careful splitting and #ifdef'ery of
> files so that we can just never link in the stuff with strings we don't
> need.

Yes, lacking a toolchain that has any vowels in it's tray I must agree.

-Mike