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Re: [Qemu-ppc] [PATCH 4/5] PPC: e500: Support platform devices

From: Alexander Graf
Subject: Re: [Qemu-ppc] [PATCH 4/5] PPC: e500: Support platform devices
Date: Thu, 19 Jun 2014 23:40:49 +0200
User-agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.9; rv:24.0) Gecko/20100101 Thunderbird/24.6.0

On 19.06.14 16:56, Eric Auger wrote:
On 06/04/2014 02:28 PM, Alexander Graf wrote:
For e500 our approach to supporting platform devices is to create a simple
bus from the guest's point of view within which we map platform devices

We allocate memory regions always within the "platform" hole in address
space and map IRQs to predetermined IRQ lines that are reserved for platform
device usage.

This maps really nicely into device tree logic, so we can just tell the
guest about our virtual simple bus in device tree as well.
Hi Alex,

this "qemu_add_machine_init_done_notifier" was the qemu mechanism I
missed in my patch. You light my way ;-)

One first comment is it would make much sense to reuse your code in arm
virt.c too. I am currently doing the exercise. Do you think it would be
possible to share a common helper code, outside of e500 machine code?

Yes, definitely :). I was mostly doing it in e500.c as a starting point. The second implementation (virt.c apparently) would then go in and commonalize everything it thinks should be common.

I'm not 100% sure where the right line is here though. For the implementation today I just throw everything into a new virtual platform bus for the guest. But there's no reason I couldn't detect "this is the first UART in my system" and put it in place where the real first UART would be in CCSR.

So yeah, again, I'm not 100% sure where the right line of distinction between board specific and generic code is here :).


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