Received-SPF: pass (google.com: domain of linux-kernel+bounces-111774-linux.lists.archive=gmail.com@vger.kernel.org designates 147.75.80.249 as permitted sender) client-ip=147.75.80.249;
Message-ID: <bcb82d05-3c8f-40f4-a8d3-a0d7c17497b3@linux.dev>
Date: Fri, 22 Mar 2024 12:26:10 -0400
Precedence: bulk
MIME-Version: 1.0
Subject: Re: [PATCH 1/2] dt-bindings: nvmem: Remove fsl,t1023-sfp in favor of
 fsl,layerscape-sfp
Content-Language: en-US
To: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>,
 Conor Dooley <conor@kernel.org>
Cc: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>,
 Richard Alpe <richard@bit42.se>, linux-kernel@vger.kernel.org,
 =?UTF-8?Q?Niklas_S=C3=B6derlund?= <niklas.soderlund@ragnatech.se>,
 Michael Walle <michael@walle.cc>,
 Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
 Conor Dooley <conor+dt@kernel.org>,
 Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
 Rob Herring <robh+dt@kernel.org>, devicetree@vger.kernel.org
References: <20240316002026.1808336-1-sean.anderson@linux.dev>
 <20240317-starved-pager-7a81c5045cfc@spud>
 <9daf9c8f-6606-4ff6-8065-6a32fa0d152c@linux.dev>
 <20240318-scarf-startup-64088b1d8d35@spud>
 <fa047914-da03-4234-b48f-eebdf350795e@linux.dev>
 <20240319-fondling-implode-322a9cb570b8@spud>
 <d947cb15-aafc-487e-8bbd-54d786683470@linux.dev>
 <024ca6eb-c3d8-4764-946e-1070d1bfb806@linaro.org>
From: Sean Anderson <sean.anderson@linux.dev>
In-Reply-To: <024ca6eb-c3d8-4764-946e-1070d1bfb806@linaro.org>
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 7bit

On 3/22/24 03:01, Krzysztof Kozlowski wrote:
> On 21/03/2024 17:21, Sean Anderson wrote:
>> On 3/19/24 13:55, Conor Dooley wrote:
>>> On Mon, Mar 18, 2024 at 11:48:06AM -0400, Sean Anderson wrote:
>>>> On 3/18/24 11:40, Conor Dooley wrote:
>>>>> On Mon, Mar 18, 2024 at 11:08:00AM -0400, Sean Anderson wrote:
>>>>>> On 3/17/24 11:10, Conor Dooley wrote:
>>>>>
>>>>>>> Additionally, should
>>>>>>> they fall back to t1023-sfp? I see that there's already some dts files
>>>>>>> with these compatibles in them but seemingly no driver support as there
>>>>>>> is for the t1023-sfp.
>>>>>>
>>>>>> I checked the reference manuals for these processors, and all of them use TA 2.0.
>>>>>
>>>>> Sounds like a fallback is suitable then, although that will require
>>>>> updating the various dts files.
>>>>
>>>> Yes, a fallback (like what is done for the T-series) would be suitable,
>>>> but given that these devicetrees have been in-tree for eight years I
>>>> think it would be preferable to support the existing bindings for
>>>> compatibility purposes.
>>>
>>> Just cos stuff snuck into the tree in dts files doesn't make it right
>>> though, I'd rather the bindings were done correctly. I don't care if you
>>> want to support all of the compatibles in the driver so that it works
>>> with the existing devicetrees though, as long as you mention the
>>> rationale in the commit message.
>> 
>> It doesn't really matter what the schema has as long as the driver supports
>> existing device trees.
> 
> We do not talk about driver now but bindings. You add new compatibles on
> a basis that they were already used. This cannot bypass regular review
> comments, so if during regular review process we would require
> fallbacks, then you are expected to listen to review also when
> documenting existing compatibles. Otherwise everyone would prefer to
> snuck in incorrect code and later document it "it was there!".

To be clear, the existing nodes look like

	sfp: sfp@e8000 {
		compatible = "fsl,t1040-sfp";
		reg	   = <0xe8000 0x1000>;
	};

which is perfectly serviceable for read-only use (as the clock is only
necessary for writing). As these devices are effectively identical, the
compatible could also look like what the P-series has:

	sfp: sfp@e8000 {
		compatible = "fsl,p2041-sfp", "fsl,qoriq-sfp-1.0";
		reg	   = <0xe8000 0x1000>;
	};

but in either case, it is desirable for the driver to match based on the
more-specific compatible (as well as the less-specific compatible) as we
already have enough information from the more-specific compatible to
select the correct implementation.

--Sean