Re: [PATCH v2 1/4] clk: Introduce clk_hw_set_spread_spectrum

Marco Felsch
2025-02-05T12:02:36Z

Hi Peng,

On 25-02-05, Peng Fan (OSS) wrote:
> From: Peng Fan <peng.fan@nxp.com>
>
> Add clk_hw_set_spread_spectrum to configure a clock to enable spread
> spectrum feature. set_spread_spectrum ops is added for clk drivers to
> have their own hardware specific implementation.
>
> Signed-off-by: Peng Fan <peng.fan@nxp.com>
> ---
> drivers/clk/clk.c | 34 ++++++++++++++++++++++++++++++++++
> include/linux/clk-provider.h | 32 ++++++++++++++++++++++++++++++++
> include/linux/clk.h | 22 ++++++++++++++++++++++
> 3 files changed, 88 insertions(+)
>
> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
> index cf7720b9172ff223d86227aad144e15375ddfd86..e11f9615e683af52c719d4c8419bd30f369f301b 100644
> --- a/drivers/clk/clk.c
> +++ b/drivers/clk/clk.c
> @@ -2790,6 +2790,40 @@ int clk_set_max_rate(struct clk *clk, unsigned long rate)
> }
> EXPORT_SYMBOL_GPL(clk_set_max_rate);
>
> +int clk_hw_set_spread_spectrum(struct clk_hw *hw, unsigned int modfreq,
> + unsigned int spreaddepth, enum clk_ssc_method method,
> + bool enable)
> +{
> + struct clk_spread_spectrum clk_ss;
> + struct clk_core *core;
> + int ret;
> +
> + if (!hw)
> + return 0;
> +
> + core = hw->core;
> +
> + clk_ss.modfreq = modfreq;
> + clk_ss.spreaddepth = spreaddepth;
> + clk_ss.method = method;
> + clk_ss.enable = enable;
> +
> + clk_prepare_lock();
> +
> + ret = clk_pm_runtime_get(core);
> + if (ret)
> + goto fail;
> +
> + if (core->ops->set_spread_spectrum)
> + ret = core->ops->set_spread_spectrum(hw, &clk_ss);
> +
> + clk_pm_runtime_put(core);
> +
> +fail:
> + clk_prepare_unlock();
> + return ret;
> +}
> +
> /**
> * clk_get_parent - return the parent of a clk
> * @clk: the clk whose parent gets returned
> diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h
> index 2e6e603b749342931c0d0693c3e72b62c000791b..ac0270cc9ec133954b1f8dcffed015723bd1ff5d 100644
> --- a/include/linux/clk-provider.h
> +++ b/include/linux/clk-provider.h
> @@ -84,6 +84,28 @@ struct clk_duty {
> unsigned int den;
> };
>
> +/* Aligned with dtschema/schemas/clock/clock.yaml */
> +enum clk_ssc_method {
> + CLK_SSC_CENTER_SPREAD,
> + CLK_SSC_UP_SPREAD,
> + CLK_SSC_DOWN_SPREAD,
> +};
> +
> +/**
> + * struct clk_spread_spectrum - Structure encoding spread spectrum of a clock
> + *
> + * @modfreq: Modulation frequency
> + * @spreadpercent: Modulation percent
> + * @method: Modulation method
> + * @enable: Modulation enable or disable
> + */
> +struct clk_spread_spectrum {
> + unsigned int modfreq;
> + unsigned int spreaddepth;

Please use per mil as unit since I noticed that 0.x% is a common value
too.

Regards,
Marco

> + enum clk_ssc_method method;
> + bool enable;
> +};
> +
> /**
> * struct clk_ops - Callback operations for hardware clocks; these are to
> * be provided by the clock implementation, and will be called by drivers
> @@ -178,6 +200,11 @@ struct clk_duty {
> * separately via calls to .set_parent and .set_rate.
> * Returns 0 on success, -EERROR otherwise.
> *
> + * @set_spread_spectrum: Configure the modulation frequency, modulation percentage
> + * and method. This callback is optional for clocks that does not
> + * support spread spectrum feature or no need to enable this feature.
> + * Returns 0 on success, -EERROR otherwise.
> + *
> * @recalc_accuracy: Recalculate the accuracy of this clock. The clock accuracy
> * is expressed in ppb (parts per billion). The parent accuracy is
> * an input parameter.
> @@ -255,6 +282,8 @@ struct clk_ops {
> int (*set_rate_and_parent)(struct clk_hw *hw,
> unsigned long rate,
> unsigned long parent_rate, u8 index);
> + int (*set_spread_spectrum)(struct clk_hw *hw,
> + struct clk_spread_spectrum *clk_ss);
> unsigned long (*recalc_accuracy)(struct clk_hw *hw,
> unsigned long parent_accuracy);
> int (*get_phase)(struct clk_hw *hw);
> @@ -1404,6 +1433,9 @@ void clk_hw_get_rate_range(struct clk_hw *hw, unsigned long *min_rate,
> unsigned long *max_rate);
> void clk_hw_set_rate_range(struct clk_hw *hw, unsigned long min_rate,
> unsigned long max_rate);
> +int clk_hw_set_spread_spectrum(struct clk_hw *hw, unsigned int modfreq,
> + unsigned int spreaddepth, enum clk_ssc_method method,
> + bool enable);
>
> static inline void __clk_hw_set_clk(struct clk_hw *dst, struct clk_hw *src)
> {
> diff --git a/include/linux/clk.h b/include/linux/clk.h
> index b607482ca77e987b9344c38f25ebb5c8d35c1d39..49a7f7eb8b03233e11cd3b92768896c4e45c4e7c 100644
> --- a/include/linux/clk.h
> +++ b/include/linux/clk.h
> @@ -858,6 +858,21 @@ int clk_set_rate(struct clk *clk, unsigned long rate);
> */
> int clk_set_rate_exclusive(struct clk *clk, unsigned long rate);
>
> +/**
> + * clk_set_spread_spectrum - set the spread spectrum for a clock
> + * @clk: clock source
> + * @modfreq: modulation freq
> + * @spreadpercent: modulation percentage
> + * @method: down spread, up spread, center spread or else
> + * @enable: enable or disable
> + *
> + * Configure the spread spectrum parameters for a clock.
> + *
> + * Returns success (0) or negative errno.
> + */
> +int clk_set_spread_spectrum(struct clk *clk, unsigned int modfreq,
> + unsigned int spreadpercent, unsigned int method,
> + bool enable);
> /**
> * clk_has_parent - check if a clock is a possible parent for another
> * @clk: clock source
> @@ -1088,6 +1103,13 @@ static inline int clk_set_rate_exclusive(struct clk *clk, unsigned long rate)
> return 0;
> }
>
> +static inline int clk_set_spread_spectrum(struct clk *clk, unsigned int modfreq,
> + unsigned int spreadpercent,
> + unsigned int method, bool enable)
> +{
> + return 0;
> +}
> +
> static inline long clk_round_rate(struct clk *clk, unsigned long rate)
> {
> return 0;
>
> --
> 2.37.1
>
>
>