RISC-V: erizo: large gap between bss and stack regions

[Sascha Hauer]

On Wed, Apr 14, 2021 at 08:54:22AM +0300, Antony Pavlov wrote:
> Hi Ahmad!
> 
> Here is the iomem command output on erizo:
> 
> barebox:/ iomem
> 0x00000000 - 0xffffffff (size 0x00000000) iomem
>   0x80000000 - 0x807fffff (size 0x00800000) ram0
>     0x804ffd00 - 0x805ffcff (size 0x00100000) malloc space
>     0x805ffd00 - 0x805fffe6 (size 0x000002e7) board data
>     0x80600000 - 0x80636b1f (size 0x00036b20) barebox
>     0x80636b20 - 0x8063ec9b (size 0x0000817c) barebox data
>     0x8063ec9c - 0x80643147 (size 0x000044ac) bss
>     0x807e0000 - 0x807fffff (size 0x00020000) stack
>   0x90000000 - 0x9000001f (size 0x00000020) 90000000.uart at 90000000.of
>   0x91000000 - 0x91000003 (size 0x00000004) 91000000.gpio at 91000000.of
>   0x91000004 - 0x91000007 (size 0x00000004) 91000000.gpio at 91000000.of
> 
> I see large unused region between bss and stack regions (>1600 Kbytes).

That's normal. The compressed barebox knows the size of the uncompressed
barebox, but it doesn't know the size of the bss segment above it. For
that reason we have a very pessimistic estimate of:

#define MAX_BSS_SIZE SZ_1M

The barebox binary itself is then aligned to the previous 1MiB
boundary, so barebox usually starts at 2MiB below the end of SDRAM.
That's a bit wasteful for boards with very little memory like the erizo,
but that's how things are at the moment.

Sascha

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