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foboot-bitstream: use new-style random rom 

Use a new pattern with a new function to generate the random ROM, used
for ROM patching.

Signed-off-by: Sean Cross <sean@xobs.io>
This commit is contained in:
Sean Cross 2019-02-25 15:16:19 +08:00
parent 21cdcaaee8
commit 49b22a1962
1 changed files with 20 additions and 5 deletions
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25
foboot-bitstream.py
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@ -82,14 +82,29 @@ class _CRG(Module):
]
class RandomFirmwareROM(wishbone.SRAM):
"""
Seed the random data with a fixed number, so different bitstreams
can all share firmware.
"""
def __init__(self, size, seed=2373):
import random
# Seed the random data with a fixed number, so different bitstreams
# can all share firmware.
random.seed(seed)
def xorshift32(x):
x = x ^ (x << 13) & 0xffffffff
x = x ^ (x >> 17) & 0xffffffff
x = x ^ (x << 5) & 0xffffffff
return x & 0xffffffff
def get_rand(x):
out = 0
for i in range(32):
x = xorshift32(x)
if (x & 1) == 1:
out = out | (1 << i)
return out & 0xffffffff
data = []
seed = 1
for d in range(int(size / 4)):
data.append(random.getrandbits(32))
seed = get_rand(seed)
data.append(seed)
print("Firmware {} bytes of random data".format(size))
wishbone.SRAM.__init__(self, size, read_only=True, init=data)