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Wed, 06 Dec 2023 09:42:34 -0800 (PST) Received: from [192.168.1.20] ([178.197.218.27]) by smtp.gmail.com with ESMTPSA id h15-20020a1709062dcf00b00a0d672bfbb0sm213002eji.142.2023.12.06.09.42.33 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 06 Dec 2023 09:42:34 -0800 (PST) Message-ID: <3fff866f-fbe8-4d23-87f3-275380adf3d4@linaro.org> Date: Wed, 6 Dec 2023 18:42:31 +0100 Precedence: bulk X-Mailing-List: devicetree@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/4] dt-bindings: memory: additional compatible strings for Broadcom DPFE Content-Language: en-US To: Florian Fainelli , Markus Mayer , Rob Herring , Conor Dooley Cc: Linux ARM Kernel List , Device Tree Mailing List , Linux Kernel Mailing List References: <20231205184741.3092376-1-mmayer@broadcom.com> <20231205184741.3092376-2-mmayer@broadcom.com> <42677f2d-190c-4043-a61d-8bfba581a764@broadcom.com> <5497447c-023b-4837-a5e2-b465ba2f624d@linaro.org> <25177e5c-880e-4c7b-8a72-2d908a970afb@broadcom.com> From: Krzysztof Kozlowski Autocrypt: addr=krzysztof.kozlowski@linaro.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 06/12/2023 18:36, Florian Fainelli wrote: > On 12/6/23 09:29, Krzysztof Kozlowski wrote: >> On 06/12/2023 17:32, Florian Fainelli wrote: >>> >>> >>> On 12/6/2023 3:09 AM, Krzysztof Kozlowski wrote: >>>> On 05/12/2023 19:47, Markus Mayer wrote: >>>>> Add versioned compatible strings for Broadcom DPFE. These take the form >>>>> brcm,dpfe-cpu-v where is a number from 1 to 4. >>>>> >>>>> These API version related compatible strings are more specific than the >>>>> catch-all "brcm,dpfe-cpu" and more generic than chip-specific compatible >>>>> strings. >>>> >>>> None of this explains: Why? I don't see any point in this and commit >>>> does not explain. >>>> >>>>> >>>>> Signed-off-by: Markus Mayer >>>>> --- >>>>> .../bindings/memory-controllers/brcm,dpfe-cpu.yaml | 8 +++++++- >>>>> 1 file changed, 7 insertions(+), 1 deletion(-) >>>>> >>>>> diff --git a/Documentation/devicetree/bindings/memory-controllers/brcm,dpfe-cpu.yaml b/Documentation/devicetree/bindings/memory-controllers/brcm,dpfe-cpu.yaml >>>>> index 08cbdcddfead..6dffa7b62baf 100644 >>>>> --- a/Documentation/devicetree/bindings/memory-controllers/brcm,dpfe-cpu.yaml >>>>> +++ b/Documentation/devicetree/bindings/memory-controllers/brcm,dpfe-cpu.yaml >>>>> @@ -16,6 +16,11 @@ properties: >>>>> - enum: >>>>> - brcm,bcm7271-dpfe-cpu >>>>> - brcm,bcm7268-dpfe-cpu >>>>> + - enum: >>>>> + - brcm,dpfe-cpu-v1 >>>>> + - brcm,dpfe-cpu-v2 >>>>> + - brcm,dpfe-cpu-v3 >>>>> + - brcm,dpfe-cpu-v4 >>>> >>>> No, that's just wrong. So you want to say bcm7271 is brcm,dpfe-cpu-v4? >>> >>> No as the example shows it "speaks" API v1. >> >> Example is not a binding. It does not matter except of validating the >> binding. This is just incorrect. >> >>> >>> I would be inclined to completely remove the chip specific compatible >>> strings from the binding because they are not sufficient or descriptive >>> enough to determine which API version is being spoken, since the >>> firmware is unfortunately allowed to change major APIs (and the >>> messaging format, because why not?) at a moments notice. >> >> Then versions do not give you anything more. > > The versions indicate exactly which API to be spoken to with the > firmware. The firmware API was not properly designed, it should have had > a way to indicate which API it has, regardless of the messaging format > it implements, but for reasons unknown that is not how it was implemented. > > Essentially we need to know right away and ahead of time which API to be > used, otherwise that means doing runtime detection like what patch 4 > does which you do not want to see. Yeah, I see, you explained this deeper in response to 3/4, which I read after this one. Deprecating specific compatibles makes sense. If you have subset of FW per given SoC, you could keep the specific compatible followed by subset of version-compatibles (e.g. bcm7271 + v1 + generic fallback). However then generic fallback is useless and you should actually drop it. The only, *ONLY* point of generic fallback is to be used by OS alone. In that case it cannot be used alone, so it is useless. We do not use generic compatibles in a way of "I want to call all of these devices a DPFE" or "I want to call it a default". Now, if you do not have subset of FW per given SoC, so anything can match with anything, then in one commit: 1. Deprecate specific compatible followed by useless generic fallback 2. Add versioned-compatibles alone, since generic fallback gives nothing. Best regards, Krzysztof