[flashrom] [PATCH] Updated vt823x "set all writes to lpc".

Luc Verhaegen libv at skynet.be
Tue Dec 22 18:41:23 CET 2009

On Tue, Dec 22, 2009 at 02:25:41PM +0100, Carl-Daniel Hailfinger wrote:
> On 22.12.2009 13:52, Luc Verhaegen wrote:
> > On Tue, Dec 22, 2009 at 03:48:38AM +0100, Carl-Daniel Hailfinger wrote:
> >   
> >> On 16.12.2009 12:14, Luc Verhaegen wrote:
> >>     
> >>> Chipset/Board: vt8237: Set All mem cycles to LPC in chipset enable.
> >>>   
> >>>       
> >> I don't have the datasheet, so I can't cross-check. I'm very interested
> >> why this would be needed, though. If mem cycles don't go to LPC and we
> >> have flash on LPC, the board won't boot anyway. If we force mem cycles
> >> to LPC although we have parallel ROM, this will break. Does VT8237R
> >> support parallel ROMs?
> >>     
> >
> > We need this, otherwise we wouldn't be changing this many board enables 
> > now.
> >   
> Ah hm. I thought most board enables were created by imitating the
> behaviour of the in-memory board enable code, not by checking for the
> necessity of each step in there.
> If there are VT8237R straps which select the ROM type, we should check
> them and warn very loudly if a board strapped to parallel gets all
> memory accesses redirected to LPC. That will make sure users know WTF
> went wrong (if something went wrong).
> > About parallel roms, no idea, but if we apply this patch, we should soon 
> > find out.
> >   
> >   
> >> Side note: Should we read the ROMCS# strap on VT8235 to check whether
> >> the ROM is LPC or Parallel? Does this strap exist for other VT823x as well?
> >>     
> The strap reading is IMHO very desirable because it can reduce the
> number of probed chips roughly by half.

The bit we are setting is the following:

ROM Memory Cycles Go To LPC
0 Disable (all memory cycles go to LPC). default.
1 Enable (only ROM memory cycles go to LPC).

What we do is set this bit to 0.

This bit is present in 8235 too, but there it seems to be not necessary.

It seems like a bug in vt8237R, and in 8237R only, as we only need to 
set it there.

Luc Verhaegen.

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