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[73.183.52.120]) by smtp.gmail.com with ESMTPSA id af79cd13be357-80aaacfeb4bsm15561385a.41.2025.09.02.15.01.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 02 Sep 2025 15:01:15 -0700 (PDT) Date: Tue, 2 Sep 2025 18:01:12 -0400 From: Brian Masney To: Peng Fan Cc: Michael Turquette , Stephen Boyd , Sudeep Holla , Cristian Marussi , Marco Felsch , Dan Carpenter , Geert Uytterhoeven , linux-clk@vger.kernel.org, linux-kernel@vger.kernel.org, arm-scmi@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH v2 1/3] clk: Introduce clk_hw_set_spread_spectrum Message-ID: References: <20250901-clk-ssc-version1-v2-0-1d0a486dffe6@nxp.com> <20250901-clk-ssc-version1-v2-1-1d0a486dffe6@nxp.com> MIME-Version: 1.0 In-Reply-To: <20250901-clk-ssc-version1-v2-1-1d0a486dffe6@nxp.com> User-Agent: Mutt/2.2.14 (2025-02-20) X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: ZTgUJ_cOzZwC-HJ43wvktM4tjRsKjJZDJxbvOp-RqH4_1756850477 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250902_150120_334401_72320005 X-CRM114-Status: GOOD ( 27.07 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, Sep 01, 2025 at 11:51:45AM +0800, Peng Fan wrote: > 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 > --- > drivers/clk/clk.c | 26 ++++++++++++++++++++++++++ > include/linux/clk-provider.h | 26 ++++++++++++++++++++++++++ > 2 files changed, 52 insertions(+) > > diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c > index b821b2cdb155331c85fafbd2fac8ab3703a08e4d..06db8918a1b35e3280e565272bc4603a88295a92 100644 > --- a/drivers/clk/clk.c > +++ b/drivers/clk/clk.c > @@ -2802,6 +2802,32 @@ 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, struct clk_spread_spectrum *conf) > +{ > + struct clk_core *core; > + int ret; > + > + if (!hw) > + return 0; > + > + core = hw->core; > + > + 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, conf); > + > + 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 630705a47129453c241f1b1755f2c2f2a7ed8f77..251035a96244c34ff2cbaaa349a08f4ea094e7fc 100644 > --- a/include/linux/clk-provider.h > +++ b/include/linux/clk-provider.h > @@ -84,6 +84,24 @@ struct clk_duty { > unsigned int den; > }; > > +#define CLK_SSC_NO_SPREAD 0 > +#define CLK_SSC_CENTER_SPREAD 1 > +#define CLK_SSC_UP_SPREAD 2 > +#define CLK_SSC_DOWN_SPREAD 3 > + > +/** > + * struct clk_spread_spectrum - Structure encoding spread spectrum of a clock > + * > + * @modfreq_hz: Modulation frequency > + * @spread_bp: Modulation percent in permyriad > + * @method: Modulation method > + */ > +struct clk_spread_spectrum { > + u32 modfreq_hz; > + u32 spread_bp; > + u32 method; > +}; > + > /** > * 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 +196,11 @@ 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. I think it would be worthwhile to call out in the kdocs that this helps to reduce EMI. How does this sound? @set_spread_spectrum: Optional callback used to configure the spread spectrum modulation frequency, percentage, and method to reduce EMI by spreading the clock frequency over a wider range. Returns 0 on success, -EERROR otherwise. Everything else looks good to me. Brian