Re: [Qemu-devel] Subject: [PATCH] target-ppc: Add global timer group A to open-pic.

[David Gibson <david@gibson.dropbear.id.au>]

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On Sun, Apr 23, 2017 at 07:37:55PM -0500, alarson@ddci.com wrote:
> David Gibson <david@gibson.dropbear.id.au> wrote on 04/23/2017 06:17:22 
> PM:
> 
> > From: David Gibson <david@gibson.dropbear.id.au>
> > To: Aaron Larson <alarson@ddci.com>
> > Cc: agraf@suse.de, qemu-devel@nongnu.org, qemu-ppc@nongnu.org
> > Date: 04/23/2017 06:54 PM
> > Subject: Re: Subject: [PATCH] target-ppc: Add global timer group A to 
> open-pic.
> > 
> > On Fri, Apr 21, 2017 at 02:58:23PM -0700, Aaron Larson wrote:
> > > Add global timer group A to open-pic.  This patch is still somewhat
> > > dubious because I'm not sure how to determine what QEMU wants for the
> > > timer frequency.  Suggestions solicited.
> > 
> > This commit message really needs some more context.  What's a "global
> > time group A" a and why do we want it?
> 
> The open-pic spec includes two sets/groups of timers, groups A and B,
> 4 timers in each group.  Previously in QEMU the timer group A
> registers were implemented but they did not "count" or generate any
> interrupts.  The patch makes the timers to do both (count and generate
> interrupts).

Ok, sounds good, but this is exactly the sort of thing that needs to
go in the commit message.

> About a year ago I mentioned that we had implemented this and offered
> to submit a patch, which seemed to be acceptable.  Sadly, when I
> reviewed the implementation it had several egregious errors that I
> didn't know how to fix until recently.

Ok.  Now that you mention that, it rings a vague bell.

> Quite frankly I didn't expect the patch to be accepted in its current
> form for the reason mentioned in the above commit log and was hoping
> for some guidance.  If this is no longer a desirable patch, I can
> certainly continue to maintain it locally for our use.

That's fine - but I need context of what the patch is attempting to
do, and why that's desirable in order to properly review it.

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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