linux-kernel - Re: [PATCH v1 04/10] clk: qcom: apss-ipq6018: ipq5332: add safe source switch for a53pll

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Message-ID: <CAA8EJppXxiX7+6nhfKyJYDU0i2pkBzXL5J3EQUapLJXxx3b=HA@mail.gmail.com>
Date:   Thu, 7 Sep 2023 16:54:56 +0300
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Varadarajan Narayanan <quic_varada@...cinc.com>
Cc:     ilia.lin@...nel.org, agross@...nel.org, andersson@...nel.org,
        konrad.dybcio@...aro.org, rafael@...nel.org,
        viresh.kumar@...aro.org, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org,
        mturquette@...libre.com, sboyd@...nel.org,
        quic_kathirav@...cinc.com, linux-pm@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-clk@...r.kernel.org
Subject: Re: [PATCH v1 04/10] clk: qcom: apss-ipq6018: ipq5332: add safe
 source switch for a53pll

On Thu, 7 Sept 2023 at 08:22, Varadarajan Narayanan
<quic_varada@...cinc.com> wrote:
>
> Stromer Plus PLL found on IPQ53xx doesn't support dynamic
> frequency scaling. To achieve the same, we need to park the APPS
> PLL source to GPLL0, re configure the PLL and then switch the
> source to APSS_PLL_EARLY.
>
> To support this, register a clock notifier to get the PRE_RATE
> and POST_RATE notification. Change the APSS PLL source to GPLL0
> when PRE_RATE notification is received, then configure the PLL
> and then change back the source to APSS_PLL_EARLY.

This means that we are changing the parents behind the back of CCF,
which is not great.

>
> Signed-off-by: Kathiravan T <quic_kathirav@...cinc.com>
> Signed-off-by: Varadarajan Narayanan <quic_varada@...cinc.com>
> ---
>  drivers/clk/qcom/apss-ipq6018.c | 54 ++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 53 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/clk/qcom/apss-ipq6018.c b/drivers/clk/qcom/apss-ipq6018.c
> index 4e13a08..ffb6ab5 100644
> --- a/drivers/clk/qcom/apss-ipq6018.c
> +++ b/drivers/clk/qcom/apss-ipq6018.c
> @@ -9,8 +9,11 @@
>  #include <linux/clk-provider.h>
>  #include <linux/regmap.h>
>  #include <linux/module.h>
> +#include <linux/clk.h>
> +#include <linux/soc/qcom/smem.h>
>
>  #include <dt-bindings/clock/qcom,apss-ipq.h>
> +#include <dt-bindings/arm/qcom,ids.h>
>
>  #include "common.h"
>  #include "clk-regmap.h"
> @@ -84,15 +87,64 @@ static const struct qcom_cc_desc apss_ipq6018_desc = {
>         .num_clks = ARRAY_SIZE(apss_ipq6018_clks),
>  };
>
> +static int cpu_clk_notifier_fn(struct notifier_block *nb, unsigned long action,
> +                               void *data)
> +{
> +       u8 index;
> +       int err;
> +
> +       if (action == PRE_RATE_CHANGE)
> +               index = P_GPLL0;

I don't see P_GPLL0 being supported in the ipq6018 driver.

> +       else if (action == POST_RATE_CHANGE)
> +               index = P_APSS_PLL_EARLY;

You also have to handle ABORT_RATE_CHANGE here.

> +       else
> +               return 0;
> +
> +       err = clk_rcg2_mux_closest_ops.set_parent(&apcs_alias0_clk_src.clkr.hw,
> +                                                 index);
> +
> +       return notifier_from_errno(err);
> +}
> +
> +static struct notifier_block cpu_clk_notifier = {
> +       .notifier_call = cpu_clk_notifier_fn,
> +};
> +
>  static int apss_ipq6018_probe(struct platform_device *pdev)
>  {
>         struct regmap *regmap;
> +       u32 soc_id;
> +       int ret;
> +
> +       ret = qcom_smem_get_soc_id(&soc_id);
> +       if (ret)
> +               return ret;
>
>         regmap = dev_get_regmap(pdev->dev.parent, NULL);
>         if (!regmap)
>                 return -ENODEV;
>
> -       return qcom_cc_really_probe(pdev, &apss_ipq6018_desc, regmap);
> +       ret = qcom_cc_really_probe(pdev, &apss_ipq6018_desc, regmap);
> +       if (ret)
> +               return ret;
> +
> +       switch (soc_id) {
> +       /*
> +        * Only below variants of IPQ53xx support scaling
> +        */
> +       case QCOM_ID_IPQ5332:
> +       case QCOM_ID_IPQ5322:
> +       case QCOM_ID_IPQ5300:

Please use compat strings instead of using the soc-id.

> +               ret = clk_notifier_register(apcs_alias0_clk_src.clkr.hw.clk,
> +                                               &cpu_clk_notifier);
> +               if (ret)
> +                       return ret;
> +               break;
> +       default:
> +               break;
> +       }
> +
> +       return 0;
>  }
>
>  static struct platform_driver apss_ipq6018_driver = {
> --
> 2.7.4
>


--
With best wishes

Dmitry