Re: [PATCH 6/6] hw/arm/aspeed: Init fby35 BMC FRUID EEPROM

[Philippe Mathieu-Daudé]

On 16/1/23 18:23, Peter Delevoryas wrote:
> On Mon, Jan 16, 2023 at 01:30:19PM +0100, Philippe Mathieu-Daudé wrote:
> > On 14/1/23 18:01, Peter Delevoryas wrote:
> > > Signed-off-by: Peter Delevoryas <peter@pjd.dev>
> > > ---
> > >    hw/arm/aspeed.c | 49 +++++++++++++++++++++++++++++++++++++++++++++++++
> > >    1 file changed, 49 insertions(+)
> > >
> > > diff --git a/hw/arm/aspeed.c b/hw/arm/aspeed.c
> > > index c929c61d582a..4ac8ff11a835 100644
> > > --- a/hw/arm/aspeed.c
> > > +++ b/hw/arm/aspeed.c
> > > @@ -922,6 +922,52 @@ static void bletchley_bmc_i2c_init(AspeedMachineState *bmc)
> > >        i2c_slave_create_simple(i2c[12], TYPE_PCA9552, 0x67);
> > >    }
> > > +static const uint8_t fby35_bmc_fruid[] = {
> > [...]
> >
> > > +};
> > > +
> > >    static void fby35_i2c_init(AspeedMachineState *bmc)
> > >    {
> > >        AspeedSoCState *soc = &bmc->soc;
> > > @@ -1363,6 +1409,9 @@ static void fby35_reset(MachineState *state, 
> > > ShutdownCause reason)
> > >        object_property_set_bool(OBJECT(gpio), "gpioB3", false, &error_fatal);
> > >        object_property_set_bool(OBJECT(gpio), "gpioB4", false, &error_fatal);
> > >        object_property_set_bool(OBJECT(gpio), "gpioB5", false, &error_fatal);
> > > +
> > > +    at24c_eeprom_write(aspeed_i2c_get_bus(&bmc->soc.i2c, 11),
> > > +                       0x54, 0, fby35_bmc_fruid, sizeof(fby35_bmc_fruid));
> >
> > Why transfer the prom content on the i2c bus at each reset?
> >
> > In particular this looks wrong if the prom is initialized with a 'drive'
> > block backend (using -global).
>
> Yeah, it looks like this might not be the right way to model it. I'm going
> to try Cedric's suggestions.

OK, but watch out this is a PROM, not a ROM, meaning it is legitimate
for a guest to reprogram it, and expect the reprogrammed content after
reset.

Shouldn't we put the 'fill default content if no -drive provided' option
in the device's realize() handler, to avoid overwriting content possibly
updated by guest before reset?