linux-kernel - Re: [PATCH 3/3] clocksource: arch_timer: Add arm,cortex-a7/15-timer in of

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Date:   Wed, 16 Mar 2022 23:11:08 +0530
From:   Kuldeep Singh <singh.kuldeep87k@...il.com>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>,
        Marc Zyngier <maz@...nel.org>
Cc:     Marc Zyngier <marc.zyngier@....com>,
        Mark Rutland <mark.rutland@....com>,
        Marc Zyngier <maz@...nel.org>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        devicetree@...r.kernel.org
Subject: Re: [PATCH 3/3] clocksource: arch_timer: Add arm,cortex-a7/15-timer
 in of_match list

On Wed, Mar 16, 2022 at 05:30:26PM +0100, Krzysztof Kozlowski wrote:
> On 16/03/2022 10:54, Kuldeep Singh wrote:
> > Few platforms such as Renesas RZ/N1D, Calxeda, Alpine etc. are using
> > arm,cortex-a15-timer and arm,cortex-a7-timer entries in conjugation with
> > arm,armv7-timer which are not currently defined in driver file. Add
> > these entries in arch_timer_of_match list to bring them in use.
> > 
> 
> This looks wrong (also Marc pointed this out) and rationale is not
> sufficient. Why do you need these compatibles in the driver?

Hi Krzysztof and Marc,

I find myself in trouble whenever dealing with compatible entries and
had 2 options when I stumble this issue.
	1. Remove unused compatible
	2. Add required compatible to binding and driver

My past experience and advise from other developer says not to remove an
existing compatible. And also I found "arm,cortex-a15-timer" in binding
which was again not documented and was present in DT. This prompted me
to go for second option and make necessary additions in binding and
driver following current entries.

As per your perspective, current configuration isn't apt which means
"arm,cortex-a15-timer" is a stub and is wrongly present in binding.

I also observed many other DTs have compatibles which are not present in
driver. What is an ideal idealogy behind such cases?

- Kuldeep