linux-kernel - Re: [PATCH 1/2] media: dt-bindings: Remove assigned-clock-* from various schema

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Message-ID: <17b5032b-8ad2-470b-8d92-41f2721930ac@kernel.org>
Date: Wed, 16 Oct 2024 09:47:32 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Rob Herring <robh@...nel.org>,
 Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc: Bryan O'Donoghue <bryan.odonoghue@...aro.org>,
 Mauro Carvalho Chehab <mchehab@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, Dave Stevenson <dave.stevenson@...pberrypi.com>,
 Sakari Ailus <sakari.ailus@...ux.intel.com>, Shawn Guo
 <shawnguo@...nel.org>, Sascha Hauer <s.hauer@...gutronix.de>,
 Pengutronix Kernel Team <kernel@...gutronix.de>,
 Fabio Estevam <festevam@...il.com>, Martin Kepplinger <martink@...teo.de>,
 Paul Kocialkowski <paul.kocialkowski@...tlin.com>,
 "Paul J. Murphy" <paul.j.murphy@...el.com>,
 Daniele Alessandrelli <daniele.alessandrelli@...el.com>,
 Tommaso Merciai <tomm.merciai@...il.com>,
 Martin Hecht <martin.hecht@...et.eu>, Zhi Mao <zhi.mao@...iatek.com>,
 Alain Volmat <alain.volmat@...s.st.com>,
 Mikhail Rudenko <mike.rudenko@...il.com>,
 Ricardo Ribalda <ribalda@...nel.org>,
 Kieran Bingham <kieran.bingham@...asonboard.com>,
 Umang Jain <umang.jain@...asonboard.com>,
 Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
 Vladimir Zapolskiy <vladimir.zapolskiy@...aro.org>,
 Dongchun Zhu <dongchun.zhu@...iatek.com>,
 Quentin Schulz <quentin.schulz@...obroma-systems.com>,
 Todor Tomov <todor.too@...il.com>, linux-media@...r.kernel.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 imx@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 1/2] media: dt-bindings: Remove assigned-clock-* from
 various schema

On 15/10/2024 18:46, Rob Herring wrote:
>>>>
>>>> How so ? Even if we assume that the device requires a specific clock
>>>> frequency (which is often not the case for camera sensors, the
>>>> limitation usually comes from drivers, so the constraint shouldn't be
>>>> expressed in the bindings in that case), there is no overall requirement
>>>> to assign a clock rate as in many cases the clock will come from a
>>>> fixed-frequency oscillator. This seems to be a constraint that is
>>>> outside of the scope of DT bindings. It is similar to regulators, where
>>>> the regulator consumer doesn't have a way to express supported voltages
>>>> in its DT bindings.
>>>
>>> This property does not say it comes from a fixed-frequency oscillator,
>>> so I do not understand why you think it is unreasonable constraint. I
>>> have no clue what the author wanted to say here, so I just explained
>>> that there is a meaning behind requiring such properties. If you claim
>>> device or implementations do not have such requirement, after
>>> investigating each case, feel free to drop this. I think I also stated
>>> this already in other reply.
>>
>> For camera sensor drivers I'm pretty sure we can drop those properties
>> when they're marked as required, as there's no intrinsic characteristics
>> of camera sensors that would require assigned-clock*.
> 
> I tend to agree, and would take it one step further to say that applies 
> everywhere. Whatever clock setup needed is outside the scope of a 
> binding. The simplest case is all input clocks are fixed. The next 
> simplest case is firmware did all clock setup needed for a specific 
> board and the boot time default works.

Ack.

Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>

Best regards,
Krzysztof