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In-Reply-To: <b995dead-5cca-de05-5840-bed882d2c4ff@linaro.org>
From:   Sergio Paracuellos <sergio.paracuellos@gmail.com>
Date:   Sat, 17 Jun 2023 21:01:09 +0200
Message-ID: <CAMhs-H-kBNKLQMgAPgt7M7wO+hcHqRiYsgqnuJYkK1NFk1jYGw@mail.gmail.com>
Subject: Re: [PATCH v4 8/9] mips: ralink: get cpu rate from new driver code
To:     Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Cc:     linux-clk@vger.kernel.org, linux-mips@vger.kernel.org,
        tsbogend@alpha.franken.de, john@phrozen.org,
        linux-kernel@vger.kernel.org, p.zabel@pengutronix.de,
        mturquette@baylibre.com, sboyd@kernel.org, robh+dt@kernel.org,
        krzysztof.kozlowski+dt@linaro.org, matthias.bgg@gmail.com,
        devicetree@vger.kernel.org, arinc.unal@arinc9.com
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On Sat, Jun 17, 2023 at 7:27=E2=80=AFPM Krzysztof Kozlowski
<krzysztof.kozlowski@linaro.org> wrote:
>
> On 17/06/2023 17:35, Sergio Paracuellos wrote:
> > On Sat, Jun 17, 2023 at 4:48=E2=80=AFPM Krzysztof Kozlowski
> > <krzysztof.kozlowski@linaro.org> wrote:
> >>
> >> On 17/06/2023 07:24, Sergio Paracuellos wrote:
> >>> At very early stage on boot, there is a need to set 'mips_hpt_frequen=
cy'.
> >>> This timer frequency is a half of the CPU frequency. To get clocks pr=
operly
> >>> set we need to call to 'of_clk_init()' and properly get cpu clock fre=
quency
> >>> afterwards. Depending on the SoC, CPU clock index in the clock provid=
er is
> >>> different being two for MT7620 SoC and one for the rest. Hence, adapt=
 code
> >>> to be aligned with new clock driver.
> >>
> >>
> >>>  void __init plat_time_init(void)
> >>>  {
> >>> +     struct of_phandle_args clkspec;
> >>>       struct clk *clk;
> >>> +     int cpu_clk_idx;
> >>>
> >>>       ralink_of_remap();
> >>>
> >>> -     ralink_clk_init();
> >>> -     clk =3D clk_get_sys("cpu", NULL);
> >>> +     cpu_clk_idx =3D clk_cpu_index();
> >>> +     if (cpu_clk_idx =3D=3D -1)
> >>> +             panic("unable to get CPU clock index");
> >>> +
> >>> +     of_clk_init(NULL);
> >>> +     clkspec.np =3D of_find_node_by_name(NULL, "sysc");
> >>> +     clkspec.args_count =3D 1;
> >>> +     clkspec.args[0] =3D cpu_clk_idx;
> >>> +     clk =3D of_clk_get_from_provider(&clkspec);
> >>
> >> This is very obfuscated way of getting clock. Why can't you get it fro=
m
> >> "clocks" property of "cpu", like every other recent platform?
> >
> > I did not find any other approach that works for me. So I ended up in t=
his one.
> > Can you point me out in a sample of code doing the same so I can check
> > if it works for me then?
>
> You mean bindings?
> git grep cpus.yaml
>
> Driver?
> git grep clk_get_rate
> clk_get
> eventually of_clk_get
>
> It all depends on the context.
>
> Anyway, it is very easy to find existing solutions not using
> of_find_node_by_name for your platform:
>
> git grep mips_hpt_frequency
>
> First result.

I have tested before all of these and got into panic because clock
cannot get retrieved:

For example first result is to make use of clk_get so change the code into:

void __init plat_time_init(void)
{
    struct clk *clk;

    of_clk_init(NULL);
    clk =3D clk_get(NULL, "cpu");
    if (IS_ERR(clk))
       panic("unable to get CPU clock, err=3D%ld", PTR_ERR(clk));

    pr_info("CPU Clock: %ldMHz\n", clk_get_rate(clk) / 1000000);
    mips_hpt_frequency =3D clk_get_rate(clk) / 2;
    clk_put(clk);
    timer_probe();
}

And I panic because I cannot get the cpu clock...

>
>
> Best regards,
> Krzysztof
>

Thanks,
    Sergio Paracuellos