Re: [PATCH 1/2] perf/arm-cmn: Fix PMU instance naming

From: Robin Murphy <robin.murphy@arm.com>
To: Will Deacon <will@kernel.org>
Cc: mark.rutland@arm.com, linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 1/2] perf/arm-cmn: Fix PMU instance naming
Date: Fri, 29 Jan 2021 00:14:55 +0000	[thread overview]
Message-ID: <07ec98a6-e773-69bd-d2fa-6737e433b43d@arm.com> (raw)
In-Reply-To: <20210128201422.GB3016@willie-the-truck>

On 2021-01-28 20:14, Will Deacon wrote:
> On Thu, Jan 28, 2021 at 01:12:43PM +0000, Robin Murphy wrote:
>> Although it's neat to avoid the suffix for the typical case of a
>> single PMU, it means systems with multiple CMN instances end up with
>> inconsistent naming. I think it also breaks perf tool's "uncore alias"
>> logic if the common instance prefix is also the full name of one.
>>
>> Avoid any surprises by not trying to be clever and simply numbering
>> every instance, even when it might technically prove redundant.
>>
>> Fixes: 0ba64770a2f2 ("perf: Add Arm CMN-600 PMU driver")
>> Signed-off-by: Robin Murphy <robin.murphy@arm.com>
>> ---
>>   Documentation/admin-guide/perf/arm-cmn.rst |  2 +-
>>   drivers/perf/arm-cmn.c                     | 13 ++++---------
>>   2 files changed, 5 insertions(+), 10 deletions(-)
> 
> Hmm, so usually I'd push-back on changes like this because it's a
> user-visible change, however in this case we're talking about a pretty
> niche PMU and a relatively new driver so I think we should proceed. However,
> if anybody complains then we'll need to support them in one way or another.

Yeah, I'm kicking myself for not remembering about the aliasing thing 
from the start - it came up tangentially from conversation with some 
interested users the other day - so hopefully the practicality will 
outweigh any possible early-adopter inconvenience.

Thanks,
Robin.

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