Re: [PATCH v5 5/9] clk: qcom: apss-ipq6018: ipq5332: add safe source switch for a53pll

[Stephen Boyd <sboyd@kernel.org>]

Quoting Varadarajan Narayanan (2023-10-19 23:19:35)
> 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.
> 
> Additionally, not all SKUs of IPQ53xx support scaling. Hence,
> do the above to the SKUs that support scaling.
> 
> Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
> Signed-off-by: Kathiravan T <quic_kathirav@quicinc.com>
> Signed-off-by: Varadarajan Narayanan <quic_varada@quicinc.com>

The Kconfig change (patch#1) should be squashed into here. Otherwise
there isn't a call to qcom_smem_get_soc_id() in the clk driver.

> ---
> v5:     clk_notifier_register -> devm_clk_notifier_register
> v3:     devm_kzalloc for cpu_clk_notifier instead of global static
> v2:     Handle ABORT_RATE_CHANGE
>         Use local variable for apcs_alias0_clk_src.clkr.hw
>         Use single line comment instead of multi line style
> ---
>  drivers/clk/qcom/apss-ipq6018.c | 58 ++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 57 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/clk/qcom/apss-ipq6018.c b/drivers/clk/qcom/apss-ipq6018.c
> index 4e13a08..e6295b8 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 +87,68 @@ 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)
> +{
> +       struct clk_hw *hw;
> +       u8 index;
> +       int err;
> +
> +       if (action == PRE_RATE_CHANGE)
> +               index = P_GPLL0;
> +       else if (action == POST_RATE_CHANGE || action == ABORT_RATE_CHANGE)
> +               index = P_APSS_PLL_EARLY;
> +       else
> +               return NOTIFY_OK;
> +
> +       hw = &apcs_alias0_clk_src.clkr.hw;
> +       err = clk_rcg2_mux_closest_ops.set_parent(hw, index);
> +
> +       return notifier_from_errno(err);
> +}
> +
>  static int apss_ipq6018_probe(struct platform_device *pdev)
>  {
> +       struct clk_hw *hw = &apcs_alias0_clk_src.clkr.hw;
> +       struct notifier_block *cpu_clk_notifier;
>         struct regmap *regmap;
> +       u32 soc_id;
> +       int ret;
> +
> +       ret = qcom_smem_get_soc_id(&soc_id);

You need to explain why this information can't come from the compatible string.

> +       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:
> +               cpu_clk_notifier = devm_kzalloc(&pdev->dev,
> +                                               sizeof(*cpu_clk_notifier),
> +                                               GFP_KERNEL);
> +               if (!cpu_clk_notifier)
> +                       return -ENOMEM;
> +