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Subject: Re: [PATCH 05/13] clk: qcom: apcs-msm8916: get parent clock names
 from DT
To:     Niklas Cassel <niklas.cassel@linaro.org>,
        Stephen Boyd <sboyd@kernel.org>
Cc:     andy.gross@linaro.org, david.brown@linaro.org,
        jassisinghbrar@gmail.com, mark.rutland@arm.com,
        mturquette@baylibre.com, robh+dt@kernel.org, will.deacon@arm.com,
        bjorn.andersson@linaro.org, vkoul@kernel.org, sibis@codeaurora.org,
        georgi.djakov@linaro.org, arnd@arndb.de,
        horms+renesas@verge.net.au, heiko@sntech.de,
        enric.balletbo@collabora.com, jagan@amarulasolutions.com,
        olof@lixom.net, amit.kucheria@linaro.org,
        devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, linux-clk@vger.kernel.org
References: <1545039990-19984-1-git-send-email-jorge.ramirez-ortiz@linaro.org>
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 <154508986359.19322.1555129141976726505@swboyd.mtv.corp.google.com>
 <20181218143503.GA32562@centauri.ideon.se>
From:   Jorge Ramirez <jorge.ramirez-ortiz@linaro.org>
Message-ID: <72bc192f-b60a-1209-7818-78a2fed07831@linaro.org>
Date:   Wed, 26 Dec 2018 10:20:07 +0100
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On 12/18/18 15:35, Niklas Cassel wrote:
> On Mon, Dec 17, 2018 at 03:37:43PM -0800, Stephen Boyd wrote:
>> Quoting Jorge Ramirez-Ortiz (2018-12-17 01:46:22)
>>> Allow accessing the parent clock names required for the driver
>>> operation by using the device tree node.
>>>
>>> This permits extending the driver to other platforms without having to
>>> modify its source code.
>>>
>>> For backwards compatibility leave previous values as default.
>>
>> Why do we need to maintain backwards compatibility? Isn't is required
>> that the nodes have clocks properties?
>>
> 
> Hello Stephen,
> 
> 
> This is the existing DT nodes for msm8916:
> 
>                 a53pll: clock@b016000 {
>                          compatible = "qcom,msm8916-a53pll";
>                          reg = <0xb016000 0x40>;
>                          #clock-cells = <0>;
>                  };
> 
>                  apcs: mailbox@b011000 {
>                          compatible = "qcom,msm8916-apcs-kpss-global", "syscon";
>                          reg = <0xb011000 0x1000>;
>                          #mbox-cells = <1>;
>                          clocks = <&a53pll>;
>                          #clock-cells = <0>;
>                  };
> 
> 
> This is the (suggested) DT nodes for qcs404:
> 
>                  apcs_hfpll: clock-controller@0b016000 {
>                          compatible = "qcom,hfpll";
>                          reg = <0x0b016000 0x30>;
>                          #clock-cells = <0>;
>                          clock-output-names = "apcs_hfpll";
>                          clocks = <&xo_board>;
>                          clock-names = "xo";
>                  };
> 
>                  apcs_glb: mailbox@b011000 {
>                          compatible = "qcom,qcs404-apcs-apps-global", "syscon";
>                          reg = <0x0b011000 0x1000>;
>                          #mbox-cells = <1>;
>                          clocks = <&gcc GCC_GPLL0_AO_OUT_MAIN>, <&apcs_hfpll>;
>                          clock-names = "aux", "pll";
>                          #clock-cells = <0>;
>                  };
> 
> qcs404 specifies two clocks, with an accompanied clock-name for each clock.
> 
> msm8916 specifies a single clock, without an accompanied clock-name.
> 
> It is possible to append clock-names = "pll" for the existing clock,
> as well as to define the aux clock in the apcs node in the msm8916 DT:
> clocks = <&gcc GPLL0_VOTE>;
> clock-names = "aux";
> 
> However, since the DT is treated as an ABI, the existing DT for msm8916 must
> still work, so I don't think that it is possible to ignore having backwards
> compability in the apcs clock driver.


so where are we with this?

do we remove backwards compatibility (see below] for v2 or is the DT 
really an ABI and therefore the patch under review is good as is?


diff --git a/arch/arm64/boot/dts/qcom/msm8916.dtsi 
b/arch/arm64/boot/dts/qcom/msm8916.dtsi
index c5348c3..729c117 100644
--- a/arch/arm64/boot/dts/qcom/msm8916.dtsi
+++ b/arch/arm64/boot/dts/qcom/msm8916.dtsi
@@ -425,7 +425,8 @@
                         compatible = "qcom,msm8916-apcs-kpss-global", 
"syscon";
                         reg = <0xb011000 0x1000>;
                         #mbox-cells = <1>;
-                   clocks = <&a53pll>;
+                 clocks = <&gcc GPLL0_VOTE>, <&a53pll>;
+                 clock-names = "aux", "pll";
                         #clock-cells = <0>;
                 };


> 
> 
> Kind regards,
> Niklas
>