linux-kernel - Re: [PATCH 2/5] clk: qcom: apcs-msm8916: get parent clock names from DT

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Date:   Mon, 9 Sep 2019 18:54:08 +0200
From:   "Jorge Ramirez-Ortiz, Linaro" <jorge.ramirez-ortiz@...aro.org>
To:     Stephen Boyd <sboyd@...nel.org>
Cc:     "Jorge Ramirez-Ortiz, Linaro" <jorge.ramirez-ortiz@...aro.org>,
        agross@...nel.org, mturquette@...libre.com,
        bjorn.andersson@...aro.org, niklas.cassel@...aro.org,
        linux-arm-msm@...r.kernel.org, linux-clk@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/5] clk: qcom: apcs-msm8916: get parent clock names from
 DT

On 09/09/19 09:17:03, Stephen Boyd wrote:
> Quoting Jorge Ramirez-Ortiz, Linaro (2019-09-09 07:17:40)
> > On 09/09/19 03:21:16, Stephen Boyd wrote:
> > > Quoting Jorge Ramirez-Ortiz (2019-08-26 09:45:07)
> > > > @@ -76,10 +88,11 @@ static int qcom_apcs_msm8916_clk_probe(struct platform_device *pdev)
> > > >         a53cc->src_shift = 8;
> > > >         a53cc->parent_map = gpll0_a53cc_map;
> > > >  
> > > > -       a53cc->pclk = devm_clk_get(parent, NULL);
> > > > +       a53cc->pclk = of_clk_get(parent->of_node, pll_index);
> > > 
> > > Presumably the PLL was always index 0, so why are we changing it to
> > > index 1 sometimes? Seems unnecessary.
> > > 
> > 
> > it came as a personal preference. hope it is acceptable (I would
> > rather not change it)
> > 
> > apcs-msm8916.c declares the following
> > 
> > [..]
> > static const u32 gpll0_a53cc_map[] = { 4, 5 };
> > static const char *gpll0_a53cc[] = {
> >        "gpll0_vote",
> >         "a53pll",
> >         };
> > [..]
> > 
> > 
> > now will be doing this
> > 
> > --- a/arch/arm64/boot/dts/qcom/msm8916.dtsi
> > +++ b/arch/arm64/boot/dts/qcom/msm8916.dtsi
> > @@ -429,7 +429,8 @@
> >      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>;
> >                };
> >                                                                                                                 
> > 
> > so I chose to keep the consistency between the clocks definition and
> > just change the index before calling of_clk_get.
> > 
> 
> But now the binding is different for the same compatible. I'd prefer we
> keep using devm_clk_get() and use a device pointer here and reorder the
> map and parent arrays instead. The clocks property shouldn't change in a
> way that isn't "additive" so that we maintain backwards compatibility.
> 

but the backwards compatibility is fully maintained - that is the main reason
behind the change. the new stuff is that  instead of hardcoding the
names in the source - like it is being done on the msm8916- we provide
the clocks in the dts node (a cleaner approach with the obvious
benefit of allowing new users to be added without having to modify the
sources).