Re: [Qemu-ppc] [PATCH 1/4] ppc4xx_i2c: Rewrite PPC4xx I2C emulation

[BALATON Zoltan]

On Wed, 6 Jun 2018, David Gibson wrote:
> On Mon, Jun 04, 2018 at 01:50:40AM +0200, BALATON Zoltan wrote:
> > I2C emulation currently is just enough for U-Boot to access SPD
> > EEPROMs but features that guests use to access I2C devices are not
> > correctly emulated. Rewrite to implement missing features to make it
> > work with all clients.
> >
> > Signed-off-by: BALATON Zoltan <address@hidden>
> > ---
> > Maybe this could be split up into more patches but because the
> > previous implementation was wrong only allowing U-Boot to pass and no
> > clients could access I2C devices before this rewrite it probably does
> > not worth to try to make it a lot of small changes instead of dropping
> > the previous hack and rewrite following features of real hardware more
> > closely. (It turns out that each client driver accesses I2C in a
> > different way so we need to implement almost all features of the
> > hardware to please everyone.)
>
> The trouble is that because I don't really have a good test setup for
> this, I'm pretty reluctant to apply such a total rewrite without acks
> from more people who've tested it.  That or reviewing the changes
> myself, which I can't really do when it's in one big lump like this.

OK, I've sent a v2 where this patch is split up to smaller pieces that are 
hopefully easier to review. However this i2c emulation was only a stub 
originally which was hacked together to make U-Boot happy when added the 
sam460ex machine and this is the first version that attempts to really 
model the device so that guests can also use it. Therefore I think there's 
not a high chance of breaking anything important. I've tested this with 
AROS, Linux, AmigaOS and MorphOS and they seem to be able to read the RTC 
so it should work better than the previous version. (Only AROS boots fully 
on sam460ex of these yet, others still need some more work.)

Regards,
BALATON Zoltan