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Re: [Qemu-devel] [PATCH v4 0/3] bugs fix for hpet


From: liu ping fan
Subject: Re: [Qemu-devel] [PATCH v4 0/3] bugs fix for hpet
Date: Wed, 4 Sep 2013 16:20:19 +0800

On Wed, Sep 4, 2013 at 3:03 PM, Paolo Bonzini <address@hidden> wrote:
> Il 04/09/2013 07:29, liu ping fan ha scritto:
>> On Tue, Sep 3, 2013 at 7:17 PM, Paolo Bonzini <address@hidden> wrote:
>>> Il 02/09/2013 09:06, Liu Ping Fan ha scritto:
>>>> note: I rebase it onto Stefan's net-next tree, since pc-1.7 has already 
>>>> been defined there.
>>>>
>>>> v4:
>>>>   use standard compat property to set hpet's interrupt compatibility
>>>>
>>>> v3:
>>>>   change hpet interrupt capablity on board's demand
>>>>
>>>>
>>>> Liu Ping Fan (3):
>>>>   hpet: inverse polarity when pin above ISA_NUM_IRQS
>>>>   hpet: entitle more irq pins for hpet
>>>>   pc-1.6: add compatibility for hpet intcap on pc-*-1.6
>>>>
>>>>  hw/timer/hpet.c      | 27 +++++++++++++++++++++++----
>>>>  include/hw/i386/pc.h |  5 +++++
>>>>  2 files changed, 28 insertions(+), 4 deletions(-)
>>>>
>>>
>>> Looks good.  But I have one question; should this be changed for PIIX
>>> too, or should the 1.7 PIIX machine keep the old behavior?  (I have no
>>> idea).
>>>
>> Your suspicion is right.  When going through PIIX4 spec, I found that
>> the chipset was without ioapic integrated. So there is divergence for
>> the compatibility of pc-piix-* and pc-q35-*.  Can I code the hpet's
>> compatiblity in pc-piix-1.7 to resolve this?
>
> You could do something like what people suggested earlier in the review.
>  Change sysbus_try_create_simple to
> qdev_try_create/sysbus_mmio_map/qdev_init in pc_basic_device_init (this
> is one patch, going before v4 3/3).  Then add a new argument to
> pc_basic_device_init, and set the intcap property if the new argument is
> nonzero (another patch, going before v4 3/3; where the new argument is
> always 0).  Finally, piix can pass 4 for the new argument, while q35 can
> keep passing 0 (squashed in v4 3/3).
>
Will follow this, thanks.

> In other words, PIIX hardcodes the value 4, while Q35 uses compat
> properties.
>
> I still have a doubt.  Can the PIIX HPET use interrupt 8?  If so, this

No. on ich9, hpet can work with LegacyReplacement Mode to block
rtc(IRQ8). But on PIIX, spec said nothing about this, so I think we
had better keep it unchanged.

Thanks and regards,
Pingfan
> won't work and we have to go back to the drawing board.  But if it can
> use interrupt 2 only, it will be okay.
>
> Paolo



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