Currently my mini-PC with AMD Ryzen CPU shows:
spdmem0 at iic0 addr 0x50: 0MB DDR4 SDRAM PC4-21300 SO-DIMM
problem here is in the calculation of the DIMM size:
dimm_size = datawidth - (chipwidth + 2);
dimm_size = ddr4_chipsize[chipsize] * (1 << dimm_size) *
(physbanks + 1) * (diecount + 1);
In my case datawidth is 3 and chipwidth is 2. So the result of the
first line is negative. Then the second line tries to do a left shift
of a negitive nunmber of bits. That doesn't really work...
Diff below fixes the issue. The "datawidth + 3" is intentional as
that is log2 of the actual bus width just like "chipwidth + 2" is log2
of the actual device width. And the former should never be smaller
than the latter.
With this I get:
spdmem0 at iic0 addr 0x50: 4GB DDR4 SDRAM PC4-21300 SO-DIMM
which looks correct as this machine has:
real mem = 3672100864 (3501MB)
avail mem = 3548086272 (3383MB)
(some memory is reserved for the GPU).
ok?
Index: dev/spdmem.c
===================================================================
RCS file: /cvs/src/sys/dev/spdmem.c,v
retrieving revision 1.6
diff -u -p -r1.6 spdmem.c
--- dev/spdmem.c 17 Dec 2019 08:01:36 -0000 1.6
+++ dev/spdmem.c 21 Dec 2019 11:06:11 -0000
@@ -770,8 +770,8 @@ spdmem_ddr4_decode(struct spdmem_softc *
SPDMEM_DDR4_PACK_TYPE_DIE_COUNT_MASK;
}
- dimm_size = datawidth - (chipwidth + 2);
- dimm_size = ddr4_chipsize[chipsize] * (1 << dimm_size) *
+ dimm_size = (datawidth + 3) - (chipwidth + 2);
+ dimm_size = (ddr4_chipsize[chipsize] / 8) * (1 << dimm_size) *
(physbanks + 1) * (diecount + 1);
if (dimm_size < 1024)
