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

[Stafford Horne <shorne@gmail.com>]

On Fri, Jun 03, 2022 at 09:05:09AM +0200, Geert Uytterhoeven wrote:
> 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.

OK, then I would think this patch would be needed on Goldfish.  I tested this
out and it seems to work:

Patch:

diff --git a/hw/rtc/goldfish_rtc.c b/hw/rtc/goldfish_rtc.c
index 35e493be31..f1dc5af297 100644
--- a/hw/rtc/goldfish_rtc.c
+++ b/hw/rtc/goldfish_rtc.c
@@ -219,7 +219,7 @@ static int goldfish_rtc_post_load(void *opaque, int
version_id)
 static const MemoryRegionOps goldfish_rtc_ops = {
     .read = goldfish_rtc_read,
     .write = goldfish_rtc_write,
-    .endianness = DEVICE_NATIVE_ENDIAN,
+    .endianness = DEVICE_LITTLE_ENDIAN,
     .valid = {
         .min_access_size = 4,
         .max_access_size = 4

Boot Log:

    io scheduler mq-deadline registered
    io scheduler kyber registered
    Serial: 8250/16550 driver, 4 ports, IRQ sharing disabled
    90000000.serial: ttyS0 at MMIO 0x90000000 (irq = 2, base_baud = 1250000) is a 16550A
    printk: console [ttyS0] enabled
    loop: module loaded
    virtio_blk virtio1: [vda] 32768 512-byte logical blocks (16.8 MB/16.0 MiB)
    Freeing initrd memory: 1696K
   *goldfish_rtc 96005000.rtc: registered as rtc0
   *goldfish_rtc 96005000.rtc: setting system clock to 2022-06-05T01:49:57 UTC (1654393797)
    NET: Registered PF_PACKET protocol family
    random: fast init done

-Stafford