[U-Boot] [PATCH] arm: socfpga: provide default SPL_SIZE_LIMIT for gen5

[Simon Goldschmidt]

Marek Vasut <marex at denx.de> schrieb am Do., 13. Juni 2019, 22:40:

> On 6/13/19 10:26 PM, Simon Goldschmidt wrote:
> >
> >
> > On 13.06.19 22:14, Marek Vasut wrote:
> >> On 6/13/19 9:50 PM, Simon Goldschmidt wrote:
> >>> This provides an SPL_SIZE_LIMIT that makes the build check that the SPL
> >>> binary loaded from flash fits into the SRAM (64 KiB) and leaves enough
> >>> room for global data, heap  and stack (512 bytes assumed stack usage).
> >>>
> >>> Signed-off-by: Simon Goldschmidt <simon.k.r.goldschmidt at gmail.com>
> >>> ---
> >>>
> >>>   arch/arm/mach-socfpga/Kconfig | 8 ++++++++
> >>>   1 file changed, 8 insertions(+)
> >>>
> >>> diff --git a/arch/arm/mach-socfpga/Kconfig
> >>> b/arch/arm/mach-socfpga/Kconfig
> >>> index 48f02f08d4..1d914648e3 100644
> >>> --- a/arch/arm/mach-socfpga/Kconfig
> >>> +++ b/arch/arm/mach-socfpga/Kconfig
> >>> @@ -3,6 +3,12 @@ if ARCH_SOCFPGA
> >>>   config NR_DRAM_BANKS
> >>>       default 1
> >>>   +config SPL_SIZE_LIMIT
> >>> +    default 65536 if TARGET_SOCFPGA_GEN5
> >>> +
> >>> +config SPL_SIZE_LIMIT_PROVIDE_STACK
> >>> +    default 0x200 if TARGET_SOCFPGA_GEN5
> >>> +
> >>>   config SPL_STACK_R_ADDR
> >>>       default 0x00800000 if TARGET_SOCFPGA_GEN5
> >>>   @@ -49,6 +55,8 @@ config TARGET_SOCFPGA_GEN5
> >>>       bool
> >>>       select SPL_ALTERA_SDRAM
> >>>       imply FPGA_SOCFPGA
> >>> +    imply SPL_SIZE_LIMIT_SUBTRACT_GD
> >>> +    imply SPL_SIZE_LIMIT_SUBTRACT_MALLOC
> >>>       imply SPL_STACK_R
> >>>       imply SPL_SYS_MALLOC_SIMPLE
> >>>       imply USE_TINY_PRINTF
> >>>
> >> 512 bytes for stack looks like it's too little. I think the SPL started
> >> misbehaving when it overgrew 50 kiB, no ?
> >
> > To 1: Well, I tested the stack usage once, booting from eMMC, and was
> > somewhere below that range. But yes, it's a problem for the future: once
> > we get a more stack-consuming function, we might be lost. Which size
> > would you suggest?
>
> Hmmm, now that I think about it, the stack gets relocated to DRAM quite
> early too, right ? So maybe we really don't need that much space for stack.
>

Exactly. The only stack-consuming things before relocation are dts parsing
and maybe the ddr driver. I implemented a stack usage check by filling the
memory with 0xaa and checking it afterwards and if I remember correctly it
resulted in about 400 bytes. It's even more or less independent of the boot
type since the ski/mmc drivers are probed only after DDR is up. Same goes
for file systems.

Nevertheless, stack usage can increase in the future. That's why I'm not
too happy about this constant. Otoh, DM_CLK makes me need every byte and
right now I don't see how I can enable secure boot (fit signature check)
due to this size limit...

Regards,
Simon


> > To 2: No. The documentation says 60 KiB would be the limit (upper 4 KiB
> > reserved for BootRom usage while loading SPL). I'm running SPL with the
> > DM_CLK driver (still under development) with a binary (code + dtb) of
> > about 58 KiB and it runs fine. Heap size before relocation increases to
> > around 4KiB though, so that ensures the 60 KiB limit isn't breached.
>
> OK, thanks for checking.
>
> --
> Best regards,
> Marek Vasut
>