How to configure MDREFR on StrongARM SA-1110

[Abraham vd M. <ab...@2d...>]

Hi!

Sorry for the cross post, but I'm not sure if all the BLOB developers are on
the linux-arm-kernel mailinglists and this question involves them as well.

I've got a StrongARM board with a DIMM on it and I can't figure out how to
configure the DRI (see MDREFR register in SA-1110 dev manual) bitfield in
the MDREFR.

The StrongARM manual talks about

((Tref - Tburst) / rows) / Fmem) / 32

where

Tref =3D refresh time of SDRAM
Tburst =3D longest burst access in _any_ memory region
Fmem =3D memory clock speed.
rows =3D row address bits

However they don't mention any units. Is Tref in ms? Tburst surely can't be
in ms right in which case that equation doesn't make sens Is Fmem in Hz?
Does the row address bits include the extra bank select bits or not?

In arch/arm/mach-sa1110/cpu-sa1110.c I see that Russel seems to do

(Tref >> rows) / 32

where Tref is in clocks which makes sense apart from the bug (it should be /
rows, not >> rows) and the fact that it doesn't take burst access into
account.

The refresh time found in SDRAM SPD's - is that per row or for the whole
module? Must be per row, since the longest possible refresh time is 125us.

I'd really appreciate it if somebody could shed some light on this.

--=20

Regards
 Abraham

Teamwork is essential -- it allows you to blame someone else.

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