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Add notes about compressed instructions

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Rodrigo Arias 2024-01-19 16:27:58 +01:00
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README.md
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@ -18,8 +18,24 @@ In u-boot use the following to boot:
=> booti 0x84000000 - ${fdtcontroladdr} => booti 0x84000000 - ${fdtcontroladdr}
``` ```
## Notes ## Use more than 1 CPU
- With only 1 CPU some thigs are soo slow to work. For example, the ttyS0 device With only 1 CPU some thigs are soo slow to work. For example, the ttyS0 device
doesn't arrive on time and the login fails. Or the SSH daemon doesn't start doesn't arrive on time and the login fails. Or the SSH daemon doesn't start
until the third try. With -smp 32 seems to work ok. until the third try. With -smp 32 seems to work ok.
## Compressed instructions
To see if a binary has compressed instructions or not, you can use objdump:
hut% nix shell -vL nixpkgs#pkgsCross.riscv64.bintools
hut% objdump -M no-aliases -D result/u-boot | grep 'c\.' | head -5
80200000: 822a c.mv tp,a0
80200002: 84ae c.mv s1,a1
80200018: 52c1 c.li t0,-16
8020001e: 0356 c.slli t1,0x15
80200024: 850a c.mv a0,sp
To dump a ROM without the ELF header:
hut% objdump -b binary -m riscv:rv64 -M no-aliases -D result/u-boot.bin