Thoughts about U-boot binary size increase

[Lukasz Majewski]

Hi Fabio,

> Hi Lukasz,
> 
> On Thu, Mar 28, 2024 at 6:20 AM Lukasz Majewski <lukma at denx.de> wrote:
> >
> > Dear Community,
> >
> > I'd like to share with you some thoughts about growth of u-boot's
> > binary size for SPL and u-boot proper.
> >
> > Board: XEA
> > SoC  : imx287 (still in active production)
> > Problem: SPL size constrained to ~55 KiB (This cannot be exceeded).
> >          Board design constraints u-boot proper size to less than
> > ~448 KiB
> >
> >
> > When XEA was added (2019.07):
> >         - u-boot.sb (SPL): 37 KiB
> >         - u-boot.img     : 401 KiB
> >
> > Now (2024.04):
> >         - u-boot.sb (SPL): 40 KiB
> >         - u-boot.img     : 427 KiB
> >
> > (With a _lot_ of effort put to reduce the size)
> >
> > Hence, the question - would it be possible to take more concern
> > about the binary size growth?
> >
> > Maybe CI could catch patches, which enable by default some features
> > and the size is unintentionally increased?
> >
> > I'm open for any feedback and thoughts on "stopping" the binary size
> > increase.  
> 
> In addition to adding CONFIG_BOARD_SIZE_LIMIT and
> CONFIG_SPL_SIZE_LIMIT checks, could you try the change below?
> 
> diff --git a/arch/arm/mach-imx/mxs/Kconfig
> b/arch/arm/mach-imx/mxs/Kconfig index d2e4205c5ce5..ee8c23d0e04f
> 100644 --- a/arch/arm/mach-imx/mxs/Kconfig
> +++ b/arch/arm/mach-imx/mxs/Kconfig
> @@ -32,6 +32,7 @@ if ARCH_MX28
> 
>  config MX28
>         bool
> +       select LTO
>         default y
> 
> I did a quick imx28_xea_defconfig build test here:
> 
> U-Boot mainline
> ---------------
> 
> $ ls -al u-boot.img
> -rw-rw-r-- 1 fabio fabio 444128 mar 28 09:11 u-boot.img
> 
> $ ls -al spl/u-boot-spl.bin
> -rwxrwxr-x 1 fabio fabio 39800 mar 28 09:12 spl/u-boot-spl.bin
> 
> 
> U-Boot mainline + LTO
> ---------------------
> 
> $ ls -al u-boot.img
> -rw-rw-r-- 1 fabio fabio 424144 mar 28 09:14 u-boot.img
> 
> $ ls -al spl/u-boot-spl.bin
> -rw-rw-r-- 1 fabio fabio 37664 mar 28 09:14 spl/u-boot-spl.bin

Thanks for the tip - I will check if enabling LTO is not causing any
regressions.


Best regards,

Lukasz Majewski

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