On Sat, Oct 01, 2005 at 10:28:07AM +0100, Ralf Baechle wrote:
> On Thu, Jun 23, 2005 at 12:01:57PM +0100, Maciej W. Rozycki wrote:
> > Well, the flag is not really to specify whether the common code is to be
> > used or not. It's about whether the TLB is like that of the R4k.
> > Actually it's always been a mystery for me why the common code cannot be
> > used for the SB1, but perhaps there is something specific that I could
> > only discover in that "SB-1 Core User Manual" that I yet have to see,
> > sigh...
> > Of course if your TLB is indeed different from that of the R4k, then you
> > shouldn't be setting cp0.config.mt to 1 in the first place...
> The reason was primarily the tiny bit of extra performance because the
> SB1 doesn't need the hazard handling overhead. Also tlb-sb1 has a few
> changes that are needed to initialize a TLB in undefined state after
> powerup. That was needed to run Linux on firmware-less SB1 cores.
FYI, all I have is a piece of hard evidence: this patch was the
difference between not booting and booting for a Sentosa with CFE.
Which isn't firmwareless and isn't a tiny bit of extra performance
I'll try to give CVS HEAD a shot this week sometime.