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Date:   Mon, 31 Jan 2022 10:41:47 -0600
From:   Bjorn Andersson <bjorn.andersson@linaro.org>
To:     Stephen Boyd <swboyd@chromium.org>
Cc:     Doug Anderson <dianders@chromium.org>,
        Viresh Kumar <viresh.kumar@linaro.org>,
        Konrad Dybcio <konrad.dybcio@somainline.org>,
        kgodara@codeaurora.org, Matthias Kaehlcke <mka@chromium.org>,
        Sibi Sankar <sibis@codeaurora.org>,
        Prasad Malisetty <pmaliset@codeaurora.org>,
        quic_rjendra@quicinc.com, Andy Gross <agross@kernel.org>,
        Rob Herring <robh+dt@kernel.org>, devicetree@vger.kernel.org,
        linux-arm-msm <linux-arm-msm@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2 5/5] arm64: dts: qcom: sc7280: Add herobrine-r1
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References: <20220125224422.544381-1-dianders@chromium.org>
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On Thu 27 Jan 15:16 CST 2022, Stephen Boyd wrote:

> Quoting Bjorn Andersson (2022-01-25 19:01:31)
> > On Tue 25 Jan 15:46 PST 2022, Doug Anderson wrote:
> >
> > > Hi,
> > >
> > > On Tue, Jan 25, 2022 at 2:58 PM Stephen Boyd <swboyd@chromium.org> wrote:
> > > >
> > > > Quoting Douglas Anderson (2022-01-25 14:44:22)
> > > > > diff --git a/arch/arm64/boot/dts/qcom/sc7280-herobrine-herobrine-r1.dts b/arch/arm64/boot/dts/qcom/sc7280-herobrine-herobrine-r1.dts
> > > > > new file mode 100644
> > > > > index 000000000000..f95273052da0
> > > > > --- /dev/null
> > > > > +++ b/arch/arm64/boot/dts/qcom/sc7280-herobrine-herobrine-r1.dts
> > > > > @@ -0,0 +1,313 @@
> > > > > +// SPDX-License-Identifier: (GPL-2.0+ OR MIT)
> > > > > +/*
> > > > > + * Google Herobrine board device tree source
> > > > > + *
> > > > > + * Copyright 2022 Google LLC.
> > > > > + */
> > > > > +
> > > > > +/dts-v1/;
> > > > > +
> > > > > +#include "sc7280-herobrine.dtsi"
> > > > > +
> > > > > +/ {
> > > > > +       model = "Google Herobrine (rev1+)";
> > > > > +       compatible = "google,herobrine", "qcom,sc7280";
> > > >
> > > > Can we stop adding "qcom,sc7280" to the board compatible string? It
> > > > looks out of place. It's the compatible for the SoC and should really be
> > > > the compatible for the /soc node.
> > >
> > > I don't have any objections, but I feel like this is the type of thing
> > > I'd like Bjorn to have the final say on. What say you, Bjorn?
> > >
> >
> > One practical case I can think of right away, where this matters is in
> > cpufreq-dt-plat.c where we blocklist qcom,sc7280.
> >
> > I don't know if we rely on this in any other places, but I'm not keen on
> > seeing a bunch of board-specific compatibles sprinkled throughout the
> > implementation - it's annoying enough having to add each platform to
> > these drivers.
> 
> Looking at sc7180, grep only shows cpufreq-dt-plat.c
> 

Good, then we handle all other platform specifics in drivers using
platform-specific compatibles.

>  $ git grep qcom,sc7180\" -- drivers
>  drivers/cpufreq/cpufreq-dt-platdev.c:   { .compatible = "qcom,sc7180", },
> 
> Simplest solution would be to look at / and /soc for a compatible
> string.
> 

You mean that / would contain the device's compatible and /soc the soc's
compatible? I'm afraid I don't see how this would help you - you still
need the compatible in the dts, just now in two places.


Either we leave it as is - which follows my interpretation of what the DT
spec says - or we (and the DT maitainers) agree that it shouldn't be
there (because this dtb won't run on any random qcom,sc7180 anyways) at
all.

Regards,
Bjorn

>  $ git grep -W 'soc[^:]*{' -- arch/arm*/boot/dts/ | grep compatible |
> grep -v "simple-bus"
> 
> doesn't show many hits. The first hit is "ti,omap-infra" which is
> actually inside an soc node, but even then I don't see anything that
> matches the cpufreq-dt-plat.c lists.
> 
> ----8<-----
> diff --git a/drivers/cpufreq/cpufreq-dt-platdev.c
> b/drivers/cpufreq/cpufreq-dt-platdev.c
> index ca1d103ec449..32bfe453f8b4 100644
> --- a/drivers/cpufreq/cpufreq-dt-platdev.c
> +++ b/drivers/cpufreq/cpufreq-dt-platdev.c
> @@ -179,25 +179,29 @@ static bool __init cpu0_node_has_opp_v2_prop(void)
>  static int __init cpufreq_dt_platdev_init(void)
>  {
>  	struct device_node *np = of_find_node_by_path("/");
> +	struct device_node *soc_np = of_find_node_by_path("/soc");
>  	const struct of_device_id *match;
>  	const void *data = NULL;
> 
> -	if (!np)
> +	if (!np && !soc_np)
>  		return -ENODEV;
> 
>  	match = of_match_node(allowlist, np);
> -	if (match) {
> +	if (match || (match = of_match_node(allowlist, soc_np))) {
>  		data = match->data;
>  		goto create_pdev;
>  	}
> 
> -	if (cpu0_node_has_opp_v2_prop() && !of_match_node(blocklist, np))
> +	if (cpu0_node_has_opp_v2_prop() && !of_match_node(blocklist, np) &&
> +	    !of_match_node(blocklist, soc_np))
>  		goto create_pdev;
> 
> +	of_node_put(soc_np);
>  	of_node_put(np);
>  	return -ENODEV;
> 
>  create_pdev:
> +	of_node_put(soc_np);
>  	of_node_put(np);
>  	return PTR_ERR_OR_ZERO(platform_device_register_data(NULL, "cpufreq-dt",
>  			       -1, data,