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

From: Scott Wood
Subject: Re: [Qemu-ppc] [Qemu-devel] [PATCH 14/19] openpic: convert to qdev
Date: Tue, 11 Dec 2012 19:38:20 -0600

On 12/11/2012 06:56:56 PM, Alexander Graf wrote:

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

> On 12/11/2012 02:25:31 AM, Alexander Graf wrote:
>> 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".

p4080 would be "fsl mpic v4.2" -- unless you want to model an older revision of p4080 in which case it could be v4.0 or v4.1. Note that this example shows that the chip name can be even less specific than the block version number.

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

"fsl mpic v2.0" describes the MPIC that was integrated into the mpc8544, as well as several other chips. In general you can look at versioned SoC blocks as if they were a separate chip, except for integration parameters, which should be qdev parameters. The only integration parameters I can think of for MPIC are the number of CPUs -- we already deviate from mpc8544 there to allow SMP -- and number of interrupt sources, for which we can safely just implement the maximum, or make it a qdev parameter if we really care about matching what hardware reports in FRR[NIRQ] (this number is actually rather useless to software the way Freescale implemented it).


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