spd_data_generate() splits @ram_size bytes into @nbanks RAM banks of
1 << sz_log2 MiB each, like this:
size = ram_size >> 20; /* work in terms of megabytes */
[...]
nbanks = 1;
while (sz_log2 > max_log2 && nbanks < 8) {
sz_log2--;
nbanks++;
}
Each iteration halves the size of a bank, and increments the number of
banks. Wrong: it should double the number of banks.
The bug goes back all the way to commit b296b664ab "smbus: Add a
helper to generate SPD EEPROM data".
It can't bite because spd_data_generate()'s current users pass only
@ram_size that result in *zero* iterations:
machine RAM size #banks type bank size
fulong2e 256 MiB 1 DDR 256 MiB
sam460ex 2048 MiB 1 DDR2 2048 MiB
1024 MiB 1 DDR2 1024 MiB
512 MiB 1 DDR2 512 MiB
256 MiB 1 DDR2 256 MiB
128 MiB 1 SDR 128 MiB
64 MiB 1 SDR 64 MiB
32 MiB 1 SDR 32 MiB
Apply the obvious, minimal fix. I admit I'm tempted to rip out the
unused (and obviously untested) feature instead, because YAGNI.
Note that this is not the final result, as spd_data_generate() next
increases #banks from 1 to 2 if possible. This is done "to avoid a
bug in MIPS Malta firmware". We don't even use this function with
machine type malta. *Shrug*
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20200422134815.1584-5-armbru@redhat.com>
32c82f0eaf