Re: [RFC PATCH 3/3] hw/openrisc: Add the OpenRISC virtual machine

[Geert Uytterhoeven]

Hi Stafford,

On Thu, Jun 2, 2022 at 9:59 PM Stafford Horne <shorne@gmail.com> wrote:
> On Thu, Jun 02, 2022 at 09:08:52PM +0200, Geert Uytterhoeven wrote:
> > On Thu, Jun 2, 2022 at 1:42 PM Joel Stanley <joel@jms.id.au> wrote:
> > > On Fri, 27 May 2022 at 17:27, Stafford Horne <shorne@gmail.com> wrote:
> > > > This patch add the OpenRISC virtual machine 'virt' for OpenRISC.  This
> > > > platform allows for a convenient CI platform for toolchain, software
> > > > ports and the OpenRISC linux kernel port.
> > > >
> > > > Much of this has been sourced from the m68k and riscv virt platforms.
> >
> > > I enabled the options:
> > >
> > > CONFIG_RTC_CLASS=y
> > > # CONFIG_RTC_SYSTOHC is not set
> > > # CONFIG_RTC_NVMEM is not set
> > > CONFIG_RTC_DRV_GOLDFISH=y
> > >
> > > But it didn't work. It seems the goldfish rtc model doesn't handle a
> > > big endian guest running on my little endian host.
> > >
> > > Doing this fixes it:
> > >
> > > -    .endianness = DEVICE_NATIVE_ENDIAN,
> > > +    .endianness = DEVICE_HOST_ENDIAN,
> > >
> > > [    0.190000] goldfish_rtc 96005000.rtc: registered as rtc0
> > > [    0.190000] goldfish_rtc 96005000.rtc: setting system clock to
> > > 2022-06-02T11:16:04 UTC (1654168564)
> > >
> > > But literally no other model in the tree does this, so I suspect it's
> > > not the right fix.
> >
> > Goldfish devices are supposed to be little endian.
> > Unfortunately m68k got this wrong, cfr.
> > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=2e2ac4a3327479f7e2744cdd88a5c823f2057bad
> > Please don't duplicate this bad behavior for new architectures
>
> Thanks for the pointer, I just wired in the goldfish RTC because I wanted to
> play with it.  I was not attached to it. I can either remove it our find 
> another
> RTC.

Sorry for being too unclear: the mistake was not to use the Goldfish
RTC, but to make its register accesses big-endian.
Using Goldfish devices as little-endian devices should be fine.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds