linux-kernel - Re: [PATCH v3 1/5] arm64/perf: Rename Cortex A57 events

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Message-ID: <20160218112429.GC8011@arm.com>
Date:	Thu, 18 Feb 2016 11:24:29 +0000
From:	Will Deacon <will.deacon@....com>
To:	Jan Glauber <jan.glauber@...iumnetworks.com>
Cc:	Mark Rutland <mark.rutland@....com>, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v3 1/5] arm64/perf: Rename Cortex A57 events

On Thu, Feb 18, 2016 at 10:13:07AM +0100, Jan Glauber wrote:
> On Mon, Feb 15, 2016 at 08:06:13PM +0000, Will Deacon wrote:
> > On Mon, Feb 15, 2016 at 07:40:37PM +0000, Will Deacon wrote:
> > > On Wed, Feb 03, 2016 at 06:11:56PM +0100, Jan Glauber wrote:
> > > > The implemented Cortex A57 events are not A57 specific.
> > > > They are recommended by ARM and can be found on other
> > > > ARMv8 SOCs like Cavium ThunderX too. Therefore move
> > > > these events to the common PMUv3 table.
> > > 
> > > I can't find anything in the architecture that suggests these event
> > > numbers are necessarily portable between implementations. Am I missing
> > > something?
> > 
> > Aha, I just noticed appendix K3.1 (silly me for missing it...).
> > 
> > Lemme check whether or not that mandates that those encodings can't be
> > used for wildly different things.
> 
> To me it looks like we would just have duplicated code without the patch,
> and at least the event types (e.g. L1D_CACHE_RD) should be identical
> across implementations.
> 
> But I don't care too much, so please tell me if should drop the patch or
> keep it.

Tell you what then -- how about we simply rename those to ARMV8_IMPDEF_*
instead of ARMV8_A57_*? That way, we can easily identify them as distinct
from the architected events if we need to in future.

Will