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@xxxxxxxxxx>
> Signed-off-by: Kathiravan T <quic_kathirav@xxxxxxxxxxx>
> Signed-off-by: Varadarajan Narayanan <quic_varada@xxxxxxxxxxx>
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;
> +
