Re: [RFC PATCH 03/14] hw/misc/bcm2835_property: Handle the 'domain state' property

[Esteban Bosse <estebanbosse@gmail.com>]

El mar, 08-10-2019 a las 11:32 +0200, Philippe Mathieu-Daudé escribió:
> On 9/29/19 9:01 AM, Esteban Bosse wrote:
> > El mié, 04-09-2019 a las 19:13 +0200, Philippe Mathieu-Daudé
> > escribió:
> > > The kernel is happy with this change, so we don't need
> > > to do anything more sophisticated.
> > > 
> > > Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
> > > Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
> > > ---
> > >   hw/misc/bcm2835_property.c | 8 ++++++++
> > >   1 file changed, 8 insertions(+)
> > > 
> > > diff --git a/hw/misc/bcm2835_property.c
> > > b/hw/misc/bcm2835_property.c
> > > index 399f0d9dd5..d8eb28f267 100644
> > > --- a/hw/misc/bcm2835_property.c
> > > +++ b/hw/misc/bcm2835_property.c
> > > @@ -127,6 +127,14 @@ static void
> > > bcm2835_property_mbox_push(BCM2835PropertyState *s, uint32_t
> > > value)
> > >               resplen = 8;
> > >               break;
> > >   
> > > +        case 0x00030030: /* Get domain state */
> > > +            qemu_log_mask(LOG_UNIMP,
> > > +                          "bcm2835_property: 0x%08x get domain
> > > state
> > > NYI\n",
> > > +                          tag);
> > > +            /* FIXME returning uninitialized memory */
> > > +            resplen = 8;
> > > +            break;
> > > +
> > >           case 0x00038002: /* Set clock rate */
> > >           case 0x00038004: /* Set max clock rate */
> > >           case 0x00038007: /* Set min clock rate */
> > 
> > Searching this property in the kernel, I found a lot of properties
> > not
> > implemented.
> > https://github.com/raspberrypi/linux/blob/rpi-4.19.y/include/soc/bcm2835/raspberrypi-firmware.h#L41
> > Are the properties only added when they are necessaries for the
> > standard kernel use?
> 
> Yes, the idea is to emulate the bare minimum required to run your
> guest 
> code. To test this series I used the closed source kernel provided
> by 
> the Raspberry Pi foundation [1] which the one that does the most of 
> UNIMP accesses, the Debian trunk one and I build one from [2].
> 
> The problem is old kernels don't support the raspi4, and recent
> kernels 
> do a lot of property calls to use recent features.
> 
> A "property call" is a call from the ARM core to the VideoCore
> firmware, 
> like a Remote Procedure Call. The ARM core write some 
> arguments/structure to a memory space shared with the VideoCore, use
> a 
> MailBox to send a 'property' key to the VideoCore and wait/poll for
> a 
> response from the VC. The VC handles the 'property' call, if
> required 
> fills the structure in the same memory space the ARM used, then
> reply 
> via another MailBox channel to notify the ARM core.
> 
> QEMU does not model the VideoCore. Instead we directly fill the
> memory 
> from the ARM property call. We fake the VC firmware.
> 
> [1] 
> https://github.com/raspberrypi/firmware/blob/master/boot/kernel8.img
> [2] https://github.com/raspberrypi/linux/tree/rpi-5.3.y
Thank you very much for all the data Phil.

Now I understood "the idea is to support the bare minimum for the
guest", I thought that the idea was a full HW support, but make sense
it's a lot of work to give full HW support.