[RFC PATCH v1] lib: rsa: introduce RSA_SOFTWARE_EXP_TINY

[Igor Opaniuk]

Hi Simon,

On Thu, Apr 29, 2021 at 7:10 PM Simon Glass <sjg at chromium.org> wrote:
>
> Hi Igor,
>
> On Fri, 16 Apr 2021 at 01:10, Igor Opaniuk <igor.opaniuk at foundries.io> wrote:
> >
> > From: Igor Opaniuk <igor.opaniuk at foundries.io>
> >
> > Introduce RSA_SOFTWARE_EXP_TINY Kconfig option, which does not require
> > DM to be enabled. This can be handy on devices, where SPL + signed
> > U-Boot FIT image setup is used, where it isn't possible to enable SPL_DM
> > mainly due to SRAM size constraits.
> >
> > For example, on iMX8MM with this option enabled and SPL_DM disabled
> > it's possible to save almost 11Kb:
>
> That seems a lot...do you have OF_PLATDATA enabled?
Nope, it's not enabled.
I've managed to get these numbers when experimenting with NXP U-Boot fork,
which is based on 2020.04.

I also checked a while ago iMX6ULL mainline U-Boot with this patch, and size
decrease was around 4-5 Kb, which basically is also not bad (considering 64Kb
SPL size limitation for this SoC).

>
> >
> > With RSA_SOFTWARE_EXP_TINY enabled:
> > spl/u-boot-spl-nodtb.bin 99824
> >
> > Without:
> > spl/u-boot-spl-nodtb.bin 111088
> >
> > Signed-off-by: Igor Opaniuk <igor.opaniuk at foundries.io>
> > ---
> >
> >  lib/rsa/Kconfig      | 11 ++++++++++-
> >  lib/rsa/rsa-verify.c |  8 ++++----
> >  2 files changed, 14 insertions(+), 5 deletions(-)
>
> Regards,
> Simon

Thanks

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Igor Opaniuk
Embedded Software Engineer
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E: igor.opaniuk at foundries.io
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