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Re: [Qemu-ppc] [Qemu-devel] [PATCH 14/19] openpic: convert to qdev

From: Alexander Graf
Subject: Re: [Qemu-ppc] [Qemu-devel] [PATCH 14/19] openpic: convert to qdev
Date: Wed, 12 Dec 2012 01:56:56 +0100

On 11.12.2012, at 18:47, Scott Wood wrote:

> On 12/11/2012 02:25:31 AM, Alexander Graf wrote:
>> On 11.12.2012, at 00:47, Scott Wood <address@hidden> wrote:
>> > On 12/08/2012 07:44:37 AM, Alexander Graf wrote:
>> >> This patch converts the OpenPIC device to qdev. Along the way it
>> >> renames the "openpic" target to "raven" and the "mpic" target to
>> >> "mpc8544", to better reflect the actual models they implement.
>> >> This way we have a generic OpenPIC device now that can handle
>> >> different flavors of the OpenPIC specification.
>> >
>> > I'd rather not see the expansion of "mpc8544" hardcoding, especially since 
>> > it's not really modelling an MPIC as found in an mpc8544, but rather 
>> > half-implementing a generic Freescale MPIC.
>> That's what we've been doing wrong all the time now. We shouldn't implement 
>> a half-generic fsl mpic, because we will never get to a point where we're 
>> accurate enough or flexible enough for both definitions.
> What do you mean by "both"?  AFAICT we'll always have a half-generic MPIC 
> because we'll probably never get it looking 100% like any particular chip.

We should be though. That's the whole point I'm making here.

>> If we want a pv style generic mpic (for -M e500), let's add such an mpic to 
>> the model list and make that one be really generic. But the MPIC in -M 
>> mpc8544ds should behave exactly like an mpc8544 mpic. Whenever we fail to do 
>> so, we better fix the emulation to be accurate ;)
> What behaviors would "mpc8544" specify that "fsl mpic v2.0" would not?

I don't know. If you say that mpc8544 == "fsl mpic v2.0" I'm more than happy to 
rename what we have. Simply calling it "MPIC" was definitely wrong, so I want 
with the one where I'm actually sure that what I'm implementing is correct, 
because I have the spec in front of me.

My general approach to this problem would be that we for example get a p4080 
board once. Once we get that, we want a p4080 MPIC. Then you'd sit down and 
model the p4080 MPIC. You realize that it's identical to the mpc8544 MPIC. So 
you either choose to instantiate an MPC8544 MPIC or you rename the model name 
to "fsl mpic v2.0".

If you can assure me today that they will be identical, I'm more than happy to 
change the name today already :).


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