linux-kernel - Re: [PATCH 05/13] clk: qcom: apcs-msm8916: get parent clock names from DT

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Message-ID: <72bc192f-b60a-1209-7818-78a2fed07831@linaro.org>
Date:   Wed, 26 Dec 2018 10:20:07 +0100
From:   Jorge Ramirez <jorge.ramirez-ortiz@...aro.org>
To:     Niklas Cassel <niklas.cassel@...aro.org>,
        Stephen Boyd <sboyd@...nel.org>
Cc:     andy.gross@...aro.org, david.brown@...aro.org,
        jassisinghbrar@...il.com, mark.rutland@....com,
        mturquette@...libre.com, robh+dt@...nel.org, will.deacon@....com,
        bjorn.andersson@...aro.org, vkoul@...nel.org, sibis@...eaurora.org,
        georgi.djakov@...aro.org, arnd@...db.de,
        horms+renesas@...ge.net.au, heiko@...ech.de,
        enric.balletbo@...labora.com, jagan@...rulasolutions.com,
        olof@...om.net, amit.kucheria@...aro.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-clk@...r.kernel.org
Subject: Re: [PATCH 05/13] clk: qcom: apcs-msm8916: get parent clock names
 from DT

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@...6000 {
>                          compatible = "qcom,msm8916-a53pll";
>                          reg = <0xb016000 0x40>;
>                          #clock-cells = <0>;
>                  };
> 
>                  apcs: mailbox@...1000 {
>                          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@...16000 {
>                          compatible = "qcom,hfpll";
>                          reg = <0x0b016000 0x30>;
>                          #clock-cells = <0>;
>                          clock-output-names = "apcs_hfpll";
>                          clocks = <&xo_board>;
>                          clock-names = "xo";
>                  };
> 
>                  apcs_glb: mailbox@...1000 {
>                          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
>