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[78.26.46.173]) by smtp.gmail.com with ESMTPSA id b16-20020a196450000000b00489e011bad7sm2948033lfj.218.2022.07.27.05.02.26 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 27 Jul 2022 05:02:27 -0700 (PDT) Message-ID: <0f5f75c3-269d-a804-7a46-9fa7aec03245@linaro.org> Date: Wed, 27 Jul 2022 14:02:26 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.12.0 Subject: Re: [[PATCH v2] 1/9] dt-bindings: pwm: Document Synopsys DesignWare snps,pwm Content-Language: en-US To: Ben Dooks , linux-pwm@vger.kernel.org Cc: devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, Lee Jones , u.kleine-koenig@pengutronix.de, Thierry Reding , Krzysztof Kozlowski , Greentime Hu References: <20220725212140.741644-1-ben.dooks@sifive.com> <922628f6-cbb1-b563-6464-e57959bafbcd@linaro.org> <8bb5103d-803e-90d2-fd93-132bb2aac2d6@sifive.com> <6317212b-1fca-65b4-9bce-0b9f7408fdae@linaro.org> <1d4573fc-407a-13c2-b049-e7a060d7929b@sifive.com> From: Krzysztof Kozlowski In-Reply-To: <1d4573fc-407a-13c2-b049-e7a060d7929b@sifive.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 27/07/2022 12:32, Ben Dooks wrote: > On 26/07/2022 12:05, Krzysztof Kozlowski wrote: >> On 26/07/2022 12:12, Ben Dooks wrote: >>> On 26/07/2022 11:05, Krzysztof Kozlowski wrote: >>>> On 25/07/2022 23:21, Ben Dooks wrote: >>>>> Add documentation for the bindings for Synopsys' DesignWare PWM block >>>>> as we will be adding DT/platform support to the Linux driver soon. >>>>> >>>>> Signed-off-by: Ben Dooks >>>>> -- >>>> >>>> This is not proper delimiter and causes the changelog to end up in commit. >>>> >>>> Correct also wrong formatting of subject PATCH. >>> >>> I realised that once sent and forgot the cover letter. >>> Maybe I'll try some more post covid recovery. >>> >>>>> v2: >>>>> - fix #pwm-cells to be 3 >>>>> - fix indentation and ordering issues >>>>> --- >>>>> .../devicetree/bindings/pwm/snps,pwm.yaml | 40 +++++++++++++++++++ >>>>> 1 file changed, 40 insertions(+) >>>>> create mode 100644 Documentation/devicetree/bindings/pwm/snps,pwm.yaml >>>>> >>>>> diff --git a/Documentation/devicetree/bindings/pwm/snps,pwm.yaml b/Documentation/devicetree/bindings/pwm/snps,pwm.yaml >>>>> new file mode 100644 >>>>> index 000000000000..594085e5e26f >>>>> --- /dev/null >>>>> +++ b/Documentation/devicetree/bindings/pwm/snps,pwm.yaml >>>>> @@ -0,0 +1,40 @@ >>>>> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause) >>>>> +# Copyright (C) 2022 SiFive, Inc. >>>>> +%YAML 1.2 >>>>> +--- >>>>> +$id: http://devicetree.org/schemas/pwm/snps,pwm.yaml# >>>>> +$schema: http://devicetree.org/meta-schemas/core.yaml# >>>>> + >>>>> +title: Synopsys PWM controller >>>>> + >>>>> +maintainers: >>>>> + - Ben Dooks >>>>> + >>>>> +allOf: >>>>> + - $ref: pwm.yaml# >>>>> + >>>>> +properties: >>>>> + compatible: >>>>> + const: snps,pwm >>>> >>>> This is very generic compatible. I doubt that you cover here all >>>> Synopsys PWM designs, past and future. You need a specific compatible. >>> >>> From what I can get from the documentation (2.13a) there hasn't been >>> a huge external interface change and what has been added is all part >>> of synthesis time options. >> >> But you have some specific version, right? Usually these blocks are >> versioned, so you must include it. I would even argue that such generic >> compatible should not be used as fallback at all, because it is simply >> to generic (PWM is not some model name but common acronym), > > I suppose dw-apb-timers is the actual document name, but that's already > been used for the timer mode in a number of SoCs so probably isn't going > to be useful. dw-apb-timers-pwm might be a better prefix if snps,pwm is > not going to be acceptable. (Yes, the block can be built as either a > PWM or a generic interrupt generating timer at IP generation time) > > As for the version numbers, we could have the -v.vv suffix for these > blocks, but the v2.xx log has 22 entries already and only one feature > for programming (which is also a configurable one so can't be just > enabled by default - it's the 0/100 mode flag in the control registers). > > I'm not sure what the v1.xx timers had, but I don't have access to this > information and we're getting these documents as second-generation so I > am not sure if we can get a v1.xx at-all (I suspect this is also going > to have a number of revisions and about 1 useful register api change > which would be the "new mode" double counter method which we currently > rely on having being implicitly enabled by the IP builder (again this > feature is still something that can be configured on IP genaration)) But why would you need v1.xx documentation? > > Given the configurability of the core, the version numbers might be > usable at some point, but it does seem to be a lot of churn for what > currently can be described by one boolean for the 0/100 feature that > might-be available. Is there a way of saying the compatible string > can be dw-apb-timers-pwm-2.[0-9][0-9][a-z] ? I don't understand why. Aren't you documenting here only v2.13a version? Best regards, Krzysztof