Re: [Qemu-devel] [PATCH 13/15] ppc4xx: Add more PLB registers

[David Gibson <david@gibson.dropbear.id.au>]

[-- Attachment #1: Type: text/plain, Size: 2517 bytes --]

On Thu, Aug 24, 2017 at 10:28:15PM +0200, BALATON Zoltan wrote:
> On Thu, 24 Aug 2017, David Gibson wrote:
> > On Wed, Aug 23, 2017 at 12:16:24PM +0200, BALATON Zoltan wrote:
> > > On Wed, 23 Aug 2017, David Gibson wrote:
> > > > On Sun, Aug 20, 2017 at 07:23:05PM +0200, BALATON Zoltan wrote:
> > > > > These registers are present in 440 SoCs (and maybe in others too) and
> > > > > U-Boot accesses them when printing register info. We don't emulate
> > > > > these but add them to avoid crashing when they are read or written.
> > > > > 
> > > > > Signed-off-by: BALATON Zoltan <balaton@eik.bme.hu>
> > > > 
> > > > I'm ok with stub implementation, but I'm a bit uncomfortable with
> > > > registering these DCRs unconditionally rather than just on the chips
> > > > that actually implement them.
> > > 
> > > Problem is that I don't know which chips have these. I can only try to find
> > > out from the U-Boot sources where a comment says these are common registers
> > > for all SoCs (in u-boot/arch/powerpc/include/asm/ppc4xx.h:
> > > 
> > > http://git.denx.de/?p=u-boot.git;a=blob;f=arch/powerpc/include/asm/ppc4xx.h;h=45ff5dbacd9243e83bb2f6551e2dd64a7e544bf5;hb=e2351d5cf1e97408b4c52bafeaa85e0ca85c920c
> > > 
> > > while looking for this I've just noticed that u-boot has removed ppc440
> > > support just before 2017.07-rc3 so this is the last version that still has
> > > these files). So if that's true it should be OK for 405 too.
> > 
> > Ok, just to make sure I'm understanding correctly are you saying:
> > 
> > 1) You suspect these registers were actually on all versions of the
> >   device, they just weren't implemented until now.
> 
> That's what I suspect from the comment in the file quoted above but I don't
> have any other evidence.
> 
> > or
> > 
> > 2) The registers are definitely on only some versions of the device,
> >   but you're not sure which ones
> 
> I don't know any of these devices very well and have no definitive sources
> to confirm so I'm not sure but I think these should be on all the versions
> (at least on all three that QEMU emulates, namely 405, 440 and
> 460ex).

Ah, ok.  I couldn't seem to find any relevant manuals either.  Ok,
given the scanty evidence we have I'm ok with including the registers
always, as proposed.

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 833 bytes --]