[PATCH v2 0/4] clk: ti: add am33xx spread spectrum clock support

[PATCH v2 0/4] clk: ti: add am33xx spread spectrum clock support

[Dario Binacchi]

As reported by the TI spruh73x RM, MPU and LCD modules support spread
spectrum clocking (SSC) on their output clocks. SSC is used to spread
the spectral peaking of the clock to reduce any electromagnetic
interference (EMI) that may be caused due to the clock’s fundamental
or any of its harmonics.
The series allows you to enable and adjust the spread spectrum clocking
for all am33xx PLLs for which it is supported.


Changes in v2:
- Remove SSC registers from dpll_core_ck@490 node (SSC is not supported)
- Add SSC registers to dpll_mpu_ck@488 node.
- Move the DT changes to the previous patch in the series.

Dario Binacchi (4):
  clk: ti: fix typo in routine description
  dt-bindings: ti: dpll: add spread spectrum support
  ARM: dts: am33xx-clocks: add spread spectrum support
  clk: ti: add am33xx spread spectrum clock support

 .../devicetree/bindings/clock/ti/dpll.txt     | 20 +++++
 arch/arm/boot/dts/am33xx-clocks.dtsi          |  4 +-
 drivers/clk/ti/dpll.c                         | 41 +++++++++
 drivers/clk/ti/dpll3xxx.c                     | 87 ++++++++++++++++++-
 include/linux/clk/ti.h                        | 24 +++++
 5 files changed, 173 insertions(+), 3 deletions(-)

-- 
2.17.1

[PATCH v2 1/4] clk: ti: fix typo in routine description

[Dario Binacchi]

Replace _omap3_noncore_dpll_program with omap3_noncore_dpll_program.

Signed-off-by: Dario Binacchi <dariobin@libero.it>
---

(no changes since v1)

 drivers/clk/ti/dpll3xxx.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/clk/ti/dpll3xxx.c b/drivers/clk/ti/dpll3xxx.c
index 6097b099a5df..94d5b5fe9a2b 100644
--- a/drivers/clk/ti/dpll3xxx.c
+++ b/drivers/clk/ti/dpll3xxx.c
@@ -292,7 +292,7 @@ static void _lookup_sddiv(struct clk_hw_omap *clk, u8 *sd_div, u16 m, u8 n)
 }
 
 /**
- * _omap3_noncore_dpll_program - set non-core DPLL M,N values directly
+ * omap3_noncore_dpll_program - set non-core DPLL M,N values directly
  * @clk:	struct clk * of DPLL to set
  * @freqsel:	FREQSEL value to set
  *
-- 
2.17.1

[PATCH v2 2/4] dt-bindings: ti: dpll: add spread spectrum support

[Dario Binacchi]

DT bindings for enabling and adjusting spread spectrum clocking have
been added.

Signed-off-by: Dario Binacchi <dariobin@libero.it>
---

(no changes since v1)

 .../devicetree/bindings/clock/ti/dpll.txt     | 20 +++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/Documentation/devicetree/bindings/clock/ti/dpll.txt b/Documentation/devicetree/bindings/clock/ti/dpll.txt
index df57009ff8e7..0810ae073294 100644
--- a/Documentation/devicetree/bindings/clock/ti/dpll.txt
+++ b/Documentation/devicetree/bindings/clock/ti/dpll.txt
@@ -42,6 +42,11 @@ Required properties:
 	"idlest" - contains the idle status register base address
 	"mult-div1" - contains the multiplier / divider register base address
 	"autoidle" - contains the autoidle register base address (optional)
+	"ssc-deltam" - DPLL supports spread spectrum clocking (SSC), contains
+		       the frequency spreading register base address (optional)
+	"ssc-modfreq" - DPLL supports spread spectrum clocking (SSC), contains
+		        the modulation frequency register base address
+			(optional)
   ti,am3-* dpll types do not have autoidle register
   ti,omap2-* dpll type does not support idlest / autoidle registers
 
@@ -51,6 +56,14 @@ Optional properties:
 	- ti,low-power-stop : DPLL supports low power stop mode, gating output
 	- ti,low-power-bypass : DPLL output matches rate of parent bypass clock
 	- ti,lock : DPLL locks in programmed rate
+	- ti,min-div : the minimum divisor to start from to round the DPLL
+		       target rate
+	- ti,ssc-deltam : DPLL supports spread spectrum clocking, frequency
+			  spreading in permille (10th of a percent)
+	- ti,ssc-modfreq : DPLL supports spread spectrum clocking, spread
+			   spectrum modulation frequency in kHz
+	- ti,ssc-downspread : DPLL supports spread spectrum clocking, boolean
+			      to enable the downspread feature
 
 Examples:
 	dpll_core_ck: dpll_core_ck@44e00490 {
@@ -83,3 +96,10 @@ Examples:
 		clocks = <&sys_ck>, <&sys_ck>;
 		reg = <0x0500>, <0x0540>;
 	};
+
+	dpll_disp_ck: dpll_disp_ck {
+		#clock-cells = <0>;
+		compatible = "ti,am3-dpll-no-gate-clock";
+		clocks = <&sys_clkin_ck>, <&sys_clkin_ck>;
+		reg = <0x0498>, <0x0448>, <0x0454>, <0x044c>, <0x0450>;
+	};
-- 
2.17.1

[PATCH v2 3/4] ARM: dts: am33xx-clocks: add spread spectrum support

[Dario Binacchi]

Registers for adjusting the spread spectrum clocking (SSC) have been
added. As reported by the TI spruh73x RM, SSC is supported only for
LCD and MPU PLLs.

Signed-off-by: Dario Binacchi <dariobin@libero.it>

---

Changes in v2:
- Remove SSC registers from dpll_core_ck@490 node (SSC is not supported)
- Add SSC registers to dpll_mpu_ck@488 node.

 arch/arm/boot/dts/am33xx-clocks.dtsi | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/arm/boot/dts/am33xx-clocks.dtsi b/arch/arm/boot/dts/am33xx-clocks.dtsi
index dced92a8970e..a02e0b1229a4 100644
--- a/arch/arm/boot/dts/am33xx-clocks.dtsi
+++ b/arch/arm/boot/dts/am33xx-clocks.dtsi
@@ -204,7 +204,7 @@
 		#clock-cells = <0>;
 		compatible = "ti,am3-dpll-clock";
 		clocks = <&sys_clkin_ck>, <&sys_clkin_ck>;
-		reg = <0x0488>, <0x0420>, <0x042c>;
+		reg = <0x0488>, <0x0420>, <0x042c>, <0x0424>, <0x0428>;
 	};
 
 	dpll_mpu_m2_ck: dpll_mpu_m2_ck@4a8 {
@@ -244,7 +244,7 @@
 		#clock-cells = <0>;
 		compatible = "ti,am3-dpll-no-gate-clock";
 		clocks = <&sys_clkin_ck>, <&sys_clkin_ck>;
-		reg = <0x0498>, <0x0448>, <0x0454>;
+		reg = <0x0498>, <0x0448>, <0x0454>, <0x044c>, <0x0450>;
 	};
 
 	dpll_disp_m2_ck: dpll_disp_m2_ck@4a4 {
-- 
2.17.1

[PATCH v2 4/4] clk: ti: add am33xx spread spectrum clock support

[Dario Binacchi]

The patch enables spread spectrum clocking (SSC) for MPU and LCD PLLs.
As reported by the TI spruh73x RM, SSC is only supported for the
DISP/LCD and MPU PLLs on am33xx device. SSC is not supported for DDR,
PER, and CORE PLLs.

Calculating the required values and setting the registers accordingly
was taken from the set_mpu_spreadspectrum routine contained in the
arch/arm/mach-omap2/am33xx/clock_am33xx.c file of the u-boot project.

In locked condition, DPLL output clock = CLKINP *[M/N]. In case of
SSC enabled, the AM335x reference manual explains that there is a
restriction of range of M values. Since the omap2_dpll_round_rate
routine attempts to select the minimum possible N, the value of M
obtained is not guaranteed to be within the range required. With the new
"ti,min-div" parameter it is possible to increase N and consequently M
to satisfy the constraint imposed by SSC.

Signed-off-by: Dario Binacchi <dariobin@libero.it>

---

Changes in v2:
- Move the DT changes to the previous patch in the series.

 drivers/clk/ti/dpll.c     | 41 +++++++++++++++++++
 drivers/clk/ti/dpll3xxx.c | 85 +++++++++++++++++++++++++++++++++++++++
 include/linux/clk/ti.h    | 24 +++++++++++
 3 files changed, 150 insertions(+)

diff --git a/drivers/clk/ti/dpll.c b/drivers/clk/ti/dpll.c
index d6f1ac5b53e1..2738417a47b7 100644
--- a/drivers/clk/ti/dpll.c
+++ b/drivers/clk/ti/dpll.c
@@ -290,7 +290,9 @@ static void __init of_ti_dpll_setup(struct device_node *node,
 	struct clk_init_data *init = NULL;
 	const char **parent_names = NULL;
 	struct dpll_data *dd = NULL;
+	int ssc_clk_index;
 	u8 dpll_mode = 0;
+	u32 min_div;
 
 	dd = kmemdup(ddt, sizeof(*dd), GFP_KERNEL);
 	clk_hw = kzalloc(sizeof(*clk_hw), GFP_KERNEL);
@@ -345,6 +347,27 @@ static void __init of_ti_dpll_setup(struct device_node *node,
 	if (dd->autoidle_mask) {
 		if (ti_clk_get_reg_addr(node, 3, &dd->autoidle_reg))
 			goto cleanup;
+
+		ssc_clk_index = 4;
+	} else {
+		ssc_clk_index = 3;
+	}
+
+	if (dd->ssc_deltam_int_mask && dd->ssc_deltam_frac_mask &&
+	    dd->ssc_modfreq_mant_mask && dd->ssc_modfreq_exp_mask) {
+		if (ti_clk_get_reg_addr(node, ssc_clk_index++,
+					&dd->ssc_deltam_reg))
+			goto cleanup;
+
+		if (ti_clk_get_reg_addr(node, ssc_clk_index++,
+					&dd->ssc_modfreq_reg))
+			goto cleanup;
+
+		of_property_read_u32(node, "ti,ssc-modfreq", &dd->ssc_modfreq);
+		of_property_read_u32(node, "ti,ssc-deltam", &dd->ssc_deltam);
+		if (of_property_read_bool(node, "ti,ssc-downspread"))
+			dd->ssc_downspread = 1;
+
 	}
 
 	if (of_property_read_bool(node, "ti,low-power-stop"))
@@ -356,6 +379,10 @@ static void __init of_ti_dpll_setup(struct device_node *node,
 	if (of_property_read_bool(node, "ti,lock"))
 		dpll_mode |= 1 << DPLL_LOCKED;
 
+	if (!of_property_read_u32(node, "ti,min-div", &min_div) &&
+	    min_div > dd->min_divider)
+		dd->min_divider = min_div;
+
 	if (dpll_mode)
 		dd->modes = dpll_mode;
 
@@ -585,8 +612,15 @@ static void __init of_ti_am3_no_gate_dpll_setup(struct device_node *node)
 	const struct dpll_data dd = {
 		.idlest_mask = 0x1,
 		.enable_mask = 0x7,
+		.ssc_enable_mask = 0x1 << 12,
+		.ssc_ack_mask = 0x1 << 13,
+		.ssc_downspread_mask = 0x1 << 14,
 		.mult_mask = 0x7ff << 8,
 		.div1_mask = 0x7f,
+		.ssc_deltam_int_mask = 0x3 << 18,
+		.ssc_deltam_frac_mask = 0x3ffff,
+		.ssc_modfreq_mant_mask = 0x7f,
+		.ssc_modfreq_exp_mask = 0x7 << 8,
 		.max_multiplier = 2047,
 		.max_divider = 128,
 		.min_divider = 1,
@@ -645,8 +679,15 @@ static void __init of_ti_am3_dpll_setup(struct device_node *node)
 	const struct dpll_data dd = {
 		.idlest_mask = 0x1,
 		.enable_mask = 0x7,
+		.ssc_enable_mask = 0x1 << 12,
+		.ssc_ack_mask = 0x1 << 13,
+		.ssc_downspread_mask = 0x1 << 14,
 		.mult_mask = 0x7ff << 8,
 		.div1_mask = 0x7f,
+		.ssc_deltam_int_mask = 0x3 << 18,
+		.ssc_deltam_frac_mask = 0x3ffff,
+		.ssc_modfreq_mant_mask = 0x7f,
+		.ssc_modfreq_exp_mask = 0x7 << 8,
 		.max_multiplier = 2047,
 		.max_divider = 128,
 		.min_divider = 1,
diff --git a/drivers/clk/ti/dpll3xxx.c b/drivers/clk/ti/dpll3xxx.c
index 94d5b5fe9a2b..e32b3515f9e7 100644
--- a/drivers/clk/ti/dpll3xxx.c
+++ b/drivers/clk/ti/dpll3xxx.c
@@ -291,6 +291,88 @@ static void _lookup_sddiv(struct clk_hw_omap *clk, u8 *sd_div, u16 m, u8 n)
 	*sd_div = sd;
 }
 
+/**
+ * omap3_noncore_dpll_ssc_program - set spread-spectrum clocking registers
+ * @clk:	struct clk * of DPLL to set
+ *
+ * Enable the DPLL spread spectrum clocking if frequency modulation and
+ * frequency spreading have been set, otherwise disable it.
+ */
+static void omap3_noncore_dpll_ssc_program(struct clk_hw_omap *clk)
+{
+	struct dpll_data *dd = clk->dpll_data;
+	unsigned long ref_rate;
+	u32 v, ctrl, mod_freq_divider, exponent, mantissa;
+	u32 deltam_step, deltam_ceil;
+
+	ctrl = ti_clk_ll_ops->clk_readl(&dd->control_reg);
+
+	if (dd->ssc_modfreq && dd->ssc_deltam) {
+		ctrl |= dd->ssc_enable_mask;
+
+		if (dd->ssc_downspread)
+			ctrl |= dd->ssc_downspread_mask;
+		else
+			ctrl &= ~dd->ssc_downspread_mask;
+
+		ref_rate = clk_hw_get_rate(dd->clk_ref);
+		mod_freq_divider =
+		    (ref_rate / dd->last_rounded_n) / (4 * dd->ssc_modfreq);
+		if (dd->ssc_modfreq > (ref_rate / 70))
+			pr_warn("clock: SSC modulation frequency of DPLL %s greater than %ld\n",
+				__clk_get_name(clk->hw.clk), ref_rate / 70);
+
+		exponent = 0;
+		mantissa = mod_freq_divider;
+		while ((mantissa > 127) && (exponent < 7)) {
+			exponent++;
+			mantissa /= 2;
+		}
+		if (mantissa > 127)
+			mantissa = 127;
+
+		v = ti_clk_ll_ops->clk_readl(&dd->ssc_modfreq_reg);
+		v &= ~(dd->ssc_modfreq_mant_mask | dd->ssc_modfreq_exp_mask);
+		v |= mantissa << __ffs(dd->ssc_modfreq_mant_mask);
+		v |= exponent << __ffs(dd->ssc_modfreq_exp_mask);
+		ti_clk_ll_ops->clk_writel(v, &dd->ssc_modfreq_reg);
+
+		deltam_step = dd->last_rounded_m * dd->ssc_deltam;
+		deltam_step /= 10;
+		if (dd->ssc_downspread)
+			deltam_step /= 2;
+
+		deltam_step <<= __ffs(dd->ssc_deltam_int_mask);
+		deltam_step /= 100;
+		deltam_step /= mod_freq_divider;
+		if (deltam_step > 0xFFFFF)
+			deltam_step = 0xFFFFF;
+
+		deltam_ceil = (deltam_step & dd->ssc_deltam_int_mask) >>
+		    __ffs(dd->ssc_deltam_int_mask);
+		if (deltam_step & dd->ssc_deltam_frac_mask)
+			deltam_ceil++;
+
+		if ((dd->ssc_downspread &&
+		     ((dd->last_rounded_m - (2 * deltam_ceil)) < 20 ||
+		      dd->last_rounded_m > 2045)) ||
+		    ((dd->last_rounded_m - deltam_ceil) < 20 ||
+		     (dd->last_rounded_m + deltam_ceil) > 2045))
+			pr_warn("clock: SSC multiplier of DPLL %s is out of range\n",
+				__clk_get_name(clk->hw.clk));
+
+		v = ti_clk_ll_ops->clk_readl(&dd->ssc_deltam_reg);
+		v &= ~(dd->ssc_deltam_int_mask | dd->ssc_deltam_frac_mask);
+		v |= deltam_step << __ffs(dd->ssc_deltam_int_mask |
+					  dd->ssc_deltam_frac_mask);
+		ti_clk_ll_ops->clk_writel(v, &dd->ssc_deltam_reg);
+	} else {
+		ctrl &= ~dd->ssc_enable_mask;
+	}
+
+	ti_clk_ll_ops->clk_writel(ctrl, &dd->control_reg);
+}
+
 /**
  * omap3_noncore_dpll_program - set non-core DPLL M,N values directly
  * @clk:	struct clk * of DPLL to set
@@ -390,6 +472,9 @@ static int omap3_noncore_dpll_program(struct clk_hw_omap *clk, u16 freqsel)
 		ti_clk_ll_ops->clk_writel(v, &dd->control_reg);
 	}
 
+	if (dd->ssc_enable_mask)
+		omap3_noncore_dpll_ssc_program(clk);
+
 	/* We let the clock framework set the other output dividers later */
 
 	/* REVISIT: Set ramp-up delay? */
diff --git a/include/linux/clk/ti.h b/include/linux/clk/ti.h
index c62f6fa6763d..cba093de62d8 100644
--- a/include/linux/clk/ti.h
+++ b/include/linux/clk/ti.h
@@ -63,6 +63,18 @@ struct clk_omap_reg {
  * @auto_recal_bit: bitshift of the driftguard enable bit in @control_reg
  * @recal_en_bit: bitshift of the PRM_IRQENABLE_* bit for recalibration IRQs
  * @recal_st_bit: bitshift of the PRM_IRQSTATUS_* bit for recalibration IRQs
+ * @ssc_deltam_reg: register containing the DPLL SSC frequency spreading
+ * @ssc_modfreq_reg: register containing the DPLL SSC modulation frequency
+ * @ssc_modfreq_mant_mask: mask of the mantissa component in @ssc_modfreq_reg
+ * @ssc_modfreq_exp_mask: mask of the exponent component in @ssc_modfreq_reg
+ * @ssc_enable_mask: mask of the DPLL SSC enable bit in @control_reg
+ * @ssc_ack_mask: mask of the DPLL SSC turned on/off bit in @control_reg
+ * @ssc_downspread_mask: mask of the DPLL SSC low frequency only bit in
+ *                       @control_reg
+ * @ssc_modfreq: the DPLL SSC frequency modulation in kHz
+ * @ssc_deltam: the DPLL SSC frequency spreading in permille (10th of percent)
+ * @ssc_downspread: require the only low frequency spread of the DPLL in SSC
+ *                   mode
  * @flags: DPLL type/features (see below)
  *
  * Possible values for @flags:
@@ -110,6 +122,18 @@ struct dpll_data {
 	u8			auto_recal_bit;
 	u8			recal_en_bit;
 	u8			recal_st_bit;
+	struct clk_omap_reg	ssc_deltam_reg;
+	struct clk_omap_reg	ssc_modfreq_reg;
+	u32			ssc_deltam_int_mask;
+	u32			ssc_deltam_frac_mask;
+	u32			ssc_modfreq_mant_mask;
+	u32			ssc_modfreq_exp_mask;
+	u32                     ssc_enable_mask;
+	u32                     ssc_ack_mask;
+	u32                     ssc_downspread_mask;
+	u32                     ssc_modfreq;
+	u32                     ssc_deltam;
+	u8                      ssc_downspread;
 	u8			flags;
 };
 
-- 
2.17.1

Re: [PATCH v2 3/4] ARM: dts: am33xx-clocks: add spread spectrum support

[Tony Lindgren]

* Dario Binacchi <dariobin@libero.it> [210318 17:28]:
> Registers for adjusting the spread spectrum clocking (SSC) have been
> added. As reported by the TI spruh73x RM, SSC is supported only for
> LCD and MPU PLLs.

Probably best to keep the series together:

Acked-by: Tony Lindgren <tony@atomide.com>

Re: [PATCH v2 2/4] dt-bindings: ti: dpll: add spread spectrum support

[Rob Herring]

On Thu, Mar 18, 2021 at 06:26:24PM +0100, Dario Binacchi wrote:
> DT bindings for enabling and adjusting spread spectrum clocking have
> been added.
> 
> Signed-off-by: Dario Binacchi <dariobin@libero.it>
> ---
> 
> (no changes since v1)
> 
>  .../devicetree/bindings/clock/ti/dpll.txt     | 20 +++++++++++++++++++
>  1 file changed, 20 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/clock/ti/dpll.txt b/Documentation/devicetree/bindings/clock/ti/dpll.txt
> index df57009ff8e7..0810ae073294 100644
> --- a/Documentation/devicetree/bindings/clock/ti/dpll.txt
> +++ b/Documentation/devicetree/bindings/clock/ti/dpll.txt
> @@ -42,6 +42,11 @@ Required properties:
>  	"idlest" - contains the idle status register base address
>  	"mult-div1" - contains the multiplier / divider register base address
>  	"autoidle" - contains the autoidle register base address (optional)
> +	"ssc-deltam" - DPLL supports spread spectrum clocking (SSC), contains
> +		       the frequency spreading register base address (optional)
> +	"ssc-modfreq" - DPLL supports spread spectrum clocking (SSC), contains
> +		        the modulation frequency register base address
> +			(optional)
>    ti,am3-* dpll types do not have autoidle register
>    ti,omap2-* dpll type does not support idlest / autoidle registers
>  
> @@ -51,6 +56,14 @@ Optional properties:
>  	- ti,low-power-stop : DPLL supports low power stop mode, gating output
>  	- ti,low-power-bypass : DPLL output matches rate of parent bypass clock
>  	- ti,lock : DPLL locks in programmed rate
> +	- ti,min-div : the minimum divisor to start from to round the DPLL
> +		       target rate
> +	- ti,ssc-deltam : DPLL supports spread spectrum clocking, frequency
> +			  spreading in permille (10th of a percent)
> +	- ti,ssc-modfreq : DPLL supports spread spectrum clocking, spread
> +			   spectrum modulation frequency in kHz

Use a standard unit suffix (-hz or -mhz).

> +	- ti,ssc-downspread : DPLL supports spread spectrum clocking, boolean
> +			      to enable the downspread feature
>  
>  Examples:
>  	dpll_core_ck: dpll_core_ck@44e00490 {
> @@ -83,3 +96,10 @@ Examples:
>  		clocks = <&sys_ck>, <&sys_ck>;
>  		reg = <0x0500>, <0x0540>;
>  	};
> +
> +	dpll_disp_ck: dpll_disp_ck {
> +		#clock-cells = <0>;
> +		compatible = "ti,am3-dpll-no-gate-clock";
> +		clocks = <&sys_clkin_ck>, <&sys_clkin_ck>;
> +		reg = <0x0498>, <0x0448>, <0x0454>, <0x044c>, <0x0450>;
> +	};
> -- 
> 2.17.1
> 

Re: [PATCH v2 1/4] clk: ti: fix typo in routine description

[Stephen Boyd]

Quoting Dario Binacchi (2021-03-18 10:26:23)
> Replace _omap3_noncore_dpll_program with omap3_noncore_dpll_program.
> 
> Signed-off-by: Dario Binacchi <dariobin@libero.it>
> ---

Reviewed-by: Stephen Boyd <sboyd@kernel.org>