Message-ID: <41e4f293-99eb-f157-b4a9-3d00b15f4652@linaro.org>
Date:   Sat, 18 Feb 2023 11:20:30 +0100
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Subject: Re: [PATCH v3 07/11] dt-bindings: clock: Add StarFive JH7110 system
 clock and reset generator
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To:     Conor Dooley <conor@kernel.org>
Cc:     Conor Dooley <conor.dooley@microchip.com>,
        Hal Feng <hal.feng@starfivetech.com>,
        linux-riscv@lists.infradead.org, devicetree@vger.kernel.org,
        linux-clk@vger.kernel.org, Palmer Dabbelt <palmer@dabbelt.com>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Stephen Boyd <sboyd@kernel.org>,
        Michael Turquette <mturquette@baylibre.com>,
        Philipp Zabel <p.zabel@pengutronix.de>,
        Emil Renner Berthing <emil.renner.berthing@canonical.com>,
        linux-kernel@vger.kernel.org
References: <Y6JB37Pd5TZoGMy4@spud>
 <7a7bccb1-4d47-3d32-36e6-4aab7b5b8dad@starfivetech.com>
 <Y6tSWB2+98a8k9Qw@spud>
 <5cf0fe71-fd17-fb28-c01e-28356081ba76@starfivetech.com>
 <Y+5z8skN2DuvxDEL@spud>
 <68e61f28-daec-ce72-726a-1fffe8e94829@starfivetech.com>
 <Y+8x/KSujhgNLAd6@wendy>
 <d3b06d0b-ff17-ebab-bae5-e1ec836fe667@starfivetech.com>
 <Y++B43uCnPQlRYFi@wendy> <dcba75b5-7b62-35aa-6836-5d5edd785002@linaro.org>
 <Y++q9ln8P3XegqfN@spud>
From:   Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
In-Reply-To: <Y++q9ln8P3XegqfN@spud>
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Precedence: bulk

On 17/02/2023 17:27, Conor Dooley wrote:
> On Fri, Feb 17, 2023 at 04:47:48PM +0100, Krzysztof Kozlowski wrote:
>> On 17/02/2023 14:32, Conor Dooley wrote:
>>>>>> Yes, it is.
>>>>>
>>>>> Which would then make GMAC1 RGMII RX optional, rather than required?
>>>>
>>>> If thinking in this way, I must say yes, it is optional. But actually
>>>> GMAC1 RGMII RX feeds gmac1_rx by default. 
>>>> For a mux, it usually works if you populate only one input to it.
>>>> Does it mean all the other inputs are optional? And how can we define
>>>> which input is required?
>>>
>>> I'm not sure, that is a question for Krzysztof and/or Rob.
>>
>> That's a long thread, please summarize what you ask. Otherwise I have no
>> clue what is the question.
> 
> Sorry. I tried to preserve the context of the conversation the last time
> I cropped it so that things would be contained on one email.
> 
> For me at least, I am wondering how you convey that out of a list of
> clock inputs (for example a, b, c, d) that two of the clocks are inputs
> to a mux and it is only required to provide one of the two (say b & c).
> 
>> Does the mux works correctly if clock input is not connected? I mean,
>> are you now talking about real hardware or some simplification from SW
>> point of view?
> 
> I'm coming at this from an angle of "is a StarFive customer going to show
> up with a devicetree containing dummy fixed-clocks to satisfy dtbs_check
> because they opted to only populate one input to the mux".
> I don't really care about implications for the driver, just about
> whether the hardware allows for inputs to the mux to be left
> un-populated.

Whether hardware allows - not a question to me. BTW, this is rather
question coming from me...

Best regards,
Krzysztof