Message-ID: <8b41827a-605a-3a65-5384-130fb0555b33@linaro.org>
Date:   Wed, 8 Feb 2023 11:27:21 +0100
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Subject: Re: [PATCH 07/15] dt-bindings: clock: Add Ambarella clock bindings
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To:     Li Chen <me@linux.beauty>
Cc:     li chen <lchen@ambarella.com>,
        michael turquette <mturquette@baylibre.com>,
        stephen boyd <sboyd@kernel.org>,
        rob herring <robh+dt@kernel.org>,
        krzysztof kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        "moderated list:arm/ambarella soc support" 
        <linux-arm-kernel@lists.infradead.org>,
        "open list:common clk framework" <linux-clk@vger.kernel.org>,
        "open list:open firmware and flattened device tree bindings" 
        <devicetree@vger.kernel.org>,
        open list <linux-kernel@vger.kernel.org>,
        arnd bergmann <arnd@arndb.de>
References: <20230123073305.149940-1-lchen@ambarella.com>
 <20230123073305.149940-8-lchen@ambarella.com>
 <0c19efb4-3bca-f500-ca24-14b9d24369ef@linaro.org>
 <87y1prgdyu.wl-me@linux.beauty>
 <b26a52ff-6b8a-8a64-7189-346cd2b0d705@linaro.org>
 <87tu0ehl88.wl-me@linux.beauty>
 <ec9fc589-2612-3315-3550-83b68bead926@linaro.org>
 <87sffyhgvw.wl-me@linux.beauty>
 <f70def8e-b148-616f-a93e-c2a8fb85be03@linaro.org>
 <185f3b3a330.11c135c37327076.6300919877819761183@linux.beauty>
 <33c2038b-5e06-4eb2-82b8-007bb735bfb1@linaro.org>
 <186267bd495.c0d336602542450.72693939722996463@linux.beauty>
 <8b164c2f-b7b9-c5df-3b9c-ea39bd3eb424@linaro.org>
 <186273b85d1.e6e326dd2609909.4901324458297607618@linux.beauty>
From:   Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
In-Reply-To: <186273b85d1.e6e326dd2609909.4901324458297607618@linux.beauty>
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On 06/02/2023 15:57, Li Chen wrote:
> Hi Krzysztof,
>  ---- On Mon, 06 Feb 2023 21:41:44 +0800  Krzysztof Kozlowski  wrote --- 
>  > On 06/02/2023 12:28, Li Chen wrote:
>  > > Hi Krzysztof ,
>  > > 
>  > >  ---- On Fri, 27 Jan 2023 23:08:09 +0800  Krzysztof Kozlowski  wrote --- 
>  > >  > On 27/01/2023 15:48, Li Chen wrote:
>  > >  > >  > 
>  > >  > >  > but what you are saying is that there is no separate clock controller
>  > >  > >  > device with its own IO address but these clocks are part of rct_syscon.
>  > >  > >  > Then model it that way in DTS. The rct_syscon is then your clock
>  > >  > >  > controller and all these fake gclk-core and gclk-ddr nodes should be gone.
>  > >  > > 
>  > >  > > Ok, I will remove these fake nodes, and model the hardware as:
>  > >  > > 
>  > >  > > rct_syscon node
>  > >  > > | clock node(pll, div, mux, composite  clocks live in the same driver)
>  > >  > > | other periphal nodes
>  > >  > 
>  > >  > You need clock node if it takes any resources. If it doesn't, you do not
>  > >  > need it.
>  > > 
>  > > If the only hardware resource the clock node can take is its parent clock(clocks = &osc;),
>  > > then can I have this clock node?
>  > 
>  > I am not sure if I understand. osc does not look like parent device, so
>  > this part of comment confuses me.
> 
> Sorry for the confusion. I mean osc is the root of clock tree:
> 
> osc
>   | pll A
>   | pll B
>   | ...
> 
> So if I have a clock node under rct_syscon node, I think it should take osc as the parent(node) clock:
> rct_syscon {
>     ......
>     clock_controller {
>           clocks = <&osc>;
>           ......
> 
> You have said "You need clock node if it takes any resources. ", do you think osc here can be counted as a used resource?

Yes, in that matter osc should be the input to this clock controller.

Best regards,
Krzysztof