linux-kernel - Re: [PATCH v5 7/7] clk: qcom: add the driver for the MSM8996 APCS clocks

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Date:   Fri, 27 Jan 2023 13:04:03 -0800
From:   Stephen Boyd <sboyd@...nel.org>
To:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Jassi Brar <jassisinghbrar@...il.com>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Michael Turquette <mturquette@...libre.com>,
        Rob Herring <robh+dt@...nel.org>,
        Taniya Das <quic_tdas@...cinc.com>
Cc:     linux-arm-msm@...r.kernel.org, linux-clk@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 7/7] clk: qcom: add the driver for the MSM8996 APCS clocks

Quoting Dmitry Baryshkov (2023-01-26 15:03:19)
> diff --git a/drivers/clk/qcom/apcs-msm8996.c b/drivers/clk/qcom/apcs-msm8996.c
> new file mode 100644
> index 000000000000..48d22572b6ae
> --- /dev/null
> +++ b/drivers/clk/qcom/apcs-msm8996.c
> @@ -0,0 +1,88 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Qualcomm APCS clock controller driver
> + *
[...]
> +
> +       /*
> +        * This clock is used during CPU cluster setup while setting up CPU PLLs.
> +        * Add hardware mandated delay to make sure that the sys_apcs_aux clock
> +        * is stable (after setting the divider) before continuing
> +        * bootstrapping to keep CPUs from ending up in a weird state.
> +        */
> +       udelay(5);
> +
> +       /*
> +        * As this clocks is a parent of the CPU cluster clocks and is actually
> +        * used as a parent during CPU clocks setup, we want for it to gegister

s/gegister/register/

> +        * as early as possible, without letting fw_devlink to delay probing of
> +        * either of the drivers.

Ok, good to know fw_devlink is the problem in this case.

> +        *
> +        * The sys_apcs_aux is a child (divider) of gpll0, but we register it
> +        * as a fixed rate clock instead to ease bootstrapping procedure. By
> +        * doing this we make sure that CPU cluster clocks are able to be setup
> +        * early during the boot process (as it is recommended by Qualcomm).
> +        */
> +       hw = devm_clk_hw_register_fixed_rate(dev, "sys_apcs_aux", NULL, 0, 300000000);
> +       if (IS_ERR(hw))
> +               return PTR_ERR(hw);
> +