[PATCH v2 0/3] clk: ti: dpll: switch spread spectrum to the generic framework

[PATCH v2 0/3] clk: ti: dpll: switch spread spectrum to the generic framework

[Dario Binacchi]

The am33xx/am43xx DPLL spread spectrum clocking (SSC) is configured
through vendor specific DT properties. Since 7.3 the clock framework
provides a generic API and the assigned-clock-sscs DT property for it,
so the series moves the TI DPLL to the generic configuration and drops
the vendor specific properties.

The last patch applies the configuration right away, as the clock
core skips set_rate() when the requested rate is already the current
one, e.g. when the bootloader has set it up.

Tested on a BeagleBone Black with equivalent parameters. The
dpll_disp_ck SSC registers are programmed with the same values as with
the vendor specific properties.

Changes in v2:
- Check the DPLL lock state instead of its parent, as the reference
  and bypass clocks can be the same clock

Dario Binacchi (3):
  dt-bindings: clock: ti: dpll: drop the ti,ssc-* properties
  clk: ti: dpll: use the generic spread spectrum configuration
  clk: ti: dpll: apply the spread spectrum configuration right away

 .../devicetree/bindings/clock/ti/dpll.txt     |  6 --
 drivers/clk/ti/clock.h                        |  2 +
 drivers/clk/ti/dpll.c                         |  8 +-
 drivers/clk/ti/dpll3xxx.c                     | 95 +++++++++++++++++--
 include/linux/clk/ti.h                        |  9 +-
 5 files changed, 91 insertions(+), 29 deletions(-)

---
base-commit: 6b4b543fa18757297ac756a6fe6e64f506b7844a
branch: am33xx-assigned-clock-sscs

-- 
2.43.0

[PATCH v2 1/3] dt-bindings: clock: ti: dpll: drop the ti,ssc-* properties

[Dario Binacchi]

The common clock binding provides assigned-clock-sscs to configure
spread spectrum clocking (SSC), supported by the clock core since commit
a7f16660af39 ("clk: conf: Support assigned-clock-sscs"). Keeping the
vendor specific ti,ssc-deltam, ti,ssc-modfreq-hz and ti,ssc-downspread
properties would leave two ways to describe the same thing.

The properties have no in-tree users, so they can be dropped.

Existing DTS files using them continue to work, with SSC disabled,
until they switch to assigned-clock-sscs.

Signed-off-by: Dario Binacchi <dario.binacchi@amarulasolutions.com>

---
If keeping the properties as deprecated is preferred, I can add a
fallback to the driver in v2.

(no changes since v1)

 Documentation/devicetree/bindings/clock/ti/dpll.txt | 6 ------
 1 file changed, 6 deletions(-)

diff --git a/Documentation/devicetree/bindings/clock/ti/dpll.txt b/Documentation/devicetree/bindings/clock/ti/dpll.txt
index 14a1b72c2e71..ffbe50f46e68 100644
--- a/Documentation/devicetree/bindings/clock/ti/dpll.txt
+++ b/Documentation/devicetree/bindings/clock/ti/dpll.txt
@@ -56,12 +56,6 @@ Optional properties:
 	- 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-hz : DPLL supports spread spectrum clocking, spread
-			      spectrum modulation frequency
-	- ti,ssc-downspread : DPLL supports spread spectrum clocking, boolean
-			      to enable the downspread feature
 
 Examples:
 	dpll_core_ck: dpll_core_ck@44e00490 {
-- 
2.43.0

Re: [PATCH v2 1/3] dt-bindings: clock: ti: dpll: drop the ti,ssc-* properties

[Krzysztof Kozlowski]

On 26/10/2026 08:46, Dario Binacchi wrote:
> The common clock binding provides assigned-clock-sscs to configure
> spread spectrum clocking (SSC), supported by the clock core since commit
> a7f16660af39 ("clk: conf: Support assigned-clock-sscs"). Keeping the
> vendor specific ti,ssc-deltam, ti,ssc-modfreq-hz and ti,ssc-downspread
> properties would leave two ways to describe the same thing.
> 
> The properties have no in-tree users, so they can be dropped.
> 
> Existing DTS files using them continue to work, with SSC disabled,
> until they switch to assigned-clock-sscs.
> 
> Signed-off-by: Dario Binacchi <dario.binacchi@amarulasolutions.com>
> 
> ---
> If keeping the properties as deprecated is preferred, I can add a
> fallback to the driver in v2.
> 
> (no changes since v1)
> 

I responded under v1, so same here:

I see the user:
	git grep ti,ssc-deltam

Maybe you ordered patches incorrectly. Anyway, properties with in-tree
users must be documented, so make them deprecated instead.

Best regards,
Krzysztof

[PATCH v2 2/3] clk: ti: dpll: use the generic spread spectrum configuration

[Dario Binacchi]

The clock framework provides a generic API and DT property for spread
spectrum clocking (SSC) since commit c86814e70390 ("clk: Introduce
clk_hw_set_spread_spectrum"). Implement the set_spread_spectrum callback
and drop the vendor specific properties.

The SSC registers are programmed at the next rate change, as with the
vendor specific properties. The generic framework expresses the spread
in permyriad rather than permille, hence the change in the deltaM step
computation, and also supports up-spread, which is rejected as the
hardware does not support it.

Signed-off-by: Dario Binacchi <dario.binacchi@amarulasolutions.com>
---

(no changes since v1)

 drivers/clk/ti/clock.h    |  2 ++
 drivers/clk/ti/dpll.c     |  8 ++---
 drivers/clk/ti/dpll3xxx.c | 61 ++++++++++++++++++++++++++++++++-------
 include/linux/clk/ti.h    |  9 ++----
 4 files changed, 57 insertions(+), 23 deletions(-)

diff --git a/drivers/clk/ti/clock.h b/drivers/clk/ti/clock.h
index d5e24fe4ae3a..83225e506314 100644
--- a/drivers/clk/ti/clock.h
+++ b/drivers/clk/ti/clock.h
@@ -271,6 +271,8 @@ int omap3_noncore_dpll_set_rate_and_parent(struct clk_hw *hw,
 					   unsigned long rate,
 					   unsigned long parent_rate,
 					   u8 index);
+int omap3_noncore_dpll_set_spread_spectrum(struct clk_hw *hw,
+					   const struct clk_spread_spectrum *ss_conf);
 int omap3_noncore_dpll_determine_rate(struct clk_hw *hw,
 				      struct clk_rate_request *req);
 int omap2_dpll_determine_rate(struct clk_hw *hw, struct clk_rate_request *req);
diff --git a/drivers/clk/ti/dpll.c b/drivers/clk/ti/dpll.c
index e01272cd628d..626b44297e42 100644
--- a/drivers/clk/ti/dpll.c
+++ b/drivers/clk/ti/dpll.c
@@ -51,6 +51,7 @@ static const struct clk_ops dpll_ck_ops = {
 	.set_parent	= &omap3_noncore_dpll_set_parent,
 	.set_rate_and_parent	= &omap3_noncore_dpll_set_rate_and_parent,
 	.determine_rate	= &omap3_noncore_dpll_determine_rate,
+	.set_spread_spectrum	= &omap3_noncore_dpll_set_spread_spectrum,
 	.get_parent	= &omap2_init_dpll_parent,
 	.save_context	= &omap3_noncore_dpll_save_context,
 	.restore_context = &omap3_noncore_dpll_restore_context,
@@ -63,6 +64,7 @@ static const struct clk_ops dpll_no_gate_ck_ops = {
 	.set_parent	= &omap3_noncore_dpll_set_parent,
 	.set_rate_and_parent	= &omap3_noncore_dpll_set_rate_and_parent,
 	.determine_rate	= &omap3_noncore_dpll_determine_rate,
+	.set_spread_spectrum	= &omap3_noncore_dpll_set_spread_spectrum,
 	.save_context	= &omap3_noncore_dpll_save_context,
 	.restore_context = &omap3_noncore_dpll_restore_context
 };
@@ -348,12 +350,6 @@ static void __init of_ti_dpll_setup(struct device_node *node,
 		if (ti_clk_get_reg_addr(node, ssc_clk_index++,
 					&dd->ssc_modfreq_reg))
 			goto cleanup;
-
-		of_property_read_u32(node, "ti,ssc-modfreq-hz",
-				     &dd->ssc_modfreq);
-		of_property_read_u32(node, "ti,ssc-deltam", &dd->ssc_deltam);
-		dd->ssc_downspread =
-			of_property_read_bool(node, "ti,ssc-downspread");
 	}
 
 	if (of_property_read_bool(node, "ti,low-power-stop"))
diff --git a/drivers/clk/ti/dpll3xxx.c b/drivers/clk/ti/dpll3xxx.c
index 8c51b988a04f..634fe0a1f9fd 100644
--- a/drivers/clk/ti/dpll3xxx.c
+++ b/drivers/clk/ti/dpll3xxx.c
@@ -295,30 +295,32 @@ static void _lookup_sddiv(struct clk_hw_omap *clk, u8 *sd_div, u16 m, u8 n)
  * 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.
+ * Enable the DPLL spread spectrum clocking according to the configuration
+ * set by omap3_noncore_dpll_set_spread_spectrum(), otherwise disable it.
  */
 static void omap3_noncore_dpll_ssc_program(struct clk_hw_omap *clk)
 {
 	struct dpll_data *dd = clk->dpll_data;
+	const struct clk_spread_spectrum *conf = &dd->ssc_conf;
+	bool downspread = conf->method == CLK_SPREAD_DOWN;
 	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) {
+	if (conf->method != CLK_SPREAD_NO) {
 		ctrl |= dd->ssc_enable_mask;
 
-		if (dd->ssc_downspread)
+		if (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))
+		    (ref_rate / dd->last_rounded_n) / (4 * conf->modfreq_hz);
+		if (conf->modfreq_hz > (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);
 
@@ -337,9 +339,10 @@ static void omap3_noncore_dpll_ssc_program(struct clk_hw_omap *clk)
 		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)
+		/* spread_bp is in permyriad, convert to percent first */
+		deltam_step = dd->last_rounded_m * conf->spread_bp;
+		deltam_step /= 100;
+		if (downspread)
 			deltam_step /= 2;
 
 		deltam_step <<= __ffs(dd->ssc_deltam_int_mask);
@@ -353,7 +356,7 @@ static void omap3_noncore_dpll_ssc_program(struct clk_hw_omap *clk)
 		if (deltam_step & dd->ssc_deltam_frac_mask)
 			deltam_ceil++;
 
-		if ((dd->ssc_downspread &&
+		if ((downspread &&
 		     ((dd->last_rounded_m - (2 * deltam_ceil)) < 20 ||
 		      dd->last_rounded_m > 2045)) ||
 		    ((dd->last_rounded_m - deltam_ceil) < 20 ||
@@ -682,6 +685,44 @@ int omap3_noncore_dpll_set_rate(struct clk_hw *hw, unsigned long rate,
 	return ret;
 }
 
+/**
+ * omap3_noncore_dpll_set_spread_spectrum - set the DPLL SSC configuration
+ * @hw: pointer to the clock to set the spread spectrum configuration for
+ * @ss_conf: spread spectrum configuration
+ *
+ * Stores the spread spectrum clocking (SSC) configuration of the DPLL. The
+ * configuration is programmed along with the DPLL multiplier and divider
+ * at the next rate change. The hardware supports center-spread and
+ * down-spread only. Returns 0 on success, or a negative error value on
+ * failure.
+ */
+int omap3_noncore_dpll_set_spread_spectrum(struct clk_hw *hw,
+					   const struct clk_spread_spectrum *ss_conf)
+{
+	struct clk_hw_omap *clk = to_clk_hw_omap(hw);
+	struct dpll_data *dd = clk->dpll_data;
+
+	if (!dd || !dd->ssc_enable_mask)
+		return -EOPNOTSUPP;
+
+	switch (ss_conf->method) {
+	case CLK_SPREAD_NO:
+		break;
+	case CLK_SPREAD_CENTER:
+	case CLK_SPREAD_DOWN:
+		if (!ss_conf->modfreq_hz || !ss_conf->spread_bp)
+			return -EINVAL;
+		break;
+	default:
+		/* Up-spread is not supported by the hardware */
+		return -EINVAL;
+	}
+
+	dd->ssc_conf = *ss_conf;
+
+	return 0;
+}
+
 /**
  * omap3_noncore_dpll_set_rate_and_parent - set rate and parent for a DPLL clock
  * @hw: pointer to the clock to set rate and parent for
diff --git a/include/linux/clk/ti.h b/include/linux/clk/ti.h
index 54a3fa370004..81ac070551f9 100644
--- a/include/linux/clk/ti.h
+++ b/include/linux/clk/ti.h
@@ -65,10 +65,7 @@ struct clk_omap_reg {
  * @ssc_enable_mask: mask of the DPLL SSC enable 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
+ * @ssc_conf: the DPLL SSC configuration, as set by clk_hw_set_spread_spectrum()
  * @flags: DPLL type/features (see below)
  *
  * Possible values for @flags:
@@ -124,9 +121,7 @@ struct dpll_data {
 	u32			ssc_modfreq_exp_mask;
 	u32                     ssc_enable_mask;
 	u32                     ssc_downspread_mask;
-	u32                     ssc_modfreq;
-	u32                     ssc_deltam;
-	bool                    ssc_downspread;
+	struct clk_spread_spectrum ssc_conf;
 	u8			flags;
 };
 
-- 
2.43.0

[PATCH v2 3/3] clk: ti: dpll: apply the spread spectrum configuration right away

[Dario Binacchi]

The spread spectrum clocking (SSC) registers are only programmed by
set_rate(), which the clock core skips when the requested rate is
already the current one, e.g. when the bootloader has set it up.
As a result, the SSC configuration is not applied, as it was with the
vendor specific properties.

Apply it from set_spread_spectrum() instead, reprogramming the DPLL
at its current rate.

Signed-off-by: Dario Binacchi <dario.binacchi@amarulasolutions.com>

---

Changes in v2:
- Check the DPLL lock state instead of its parent, as the reference
  and bypass clocks can be the same clock

 drivers/clk/ti/dpll3xxx.c | 46 ++++++++++++++++++++++++++++++++++-----
 1 file changed, 40 insertions(+), 6 deletions(-)

diff --git a/drivers/clk/ti/dpll3xxx.c b/drivers/clk/ti/dpll3xxx.c
index 634fe0a1f9fd..16da86fbb25d 100644
--- a/drivers/clk/ti/dpll3xxx.c
+++ b/drivers/clk/ti/dpll3xxx.c
@@ -690,17 +690,22 @@ int omap3_noncore_dpll_set_rate(struct clk_hw *hw, unsigned long rate,
  * @hw: pointer to the clock to set the spread spectrum configuration for
  * @ss_conf: spread spectrum configuration
  *
- * Stores the spread spectrum clocking (SSC) configuration of the DPLL. The
- * configuration is programmed along with the DPLL multiplier and divider
- * at the next rate change. The hardware supports center-spread and
- * down-spread only. Returns 0 on success, or a negative error value on
- * failure.
+ * Stores the spread spectrum clocking (SSC) configuration of the DPLL and,
+ * if the DPLL is locked, reprograms it at its current rate to apply it.
+ * Otherwise the configuration is applied at the next rate change. The
+ * hardware supports center-spread and down-spread only. Returns 0 on
+ * success, negative error value otherwise.
  */
 int omap3_noncore_dpll_set_spread_spectrum(struct clk_hw *hw,
 					   const struct clk_spread_spectrum *ss_conf)
 {
 	struct clk_hw_omap *clk = to_clk_hw_omap(hw);
 	struct dpll_data *dd = clk->dpll_data;
+	struct clk_spread_spectrum old_conf;
+	struct clk_rate_request req;
+	unsigned long rate;
+	int ret;
+	u32 ctrl;
 
 	if (!dd || !dd->ssc_enable_mask)
 		return -EOPNOTSUPP;
@@ -718,9 +723,38 @@ int omap3_noncore_dpll_set_spread_spectrum(struct clk_hw *hw,
 		return -EINVAL;
 	}
 
+	if (!memcmp(ss_conf, &dd->ssc_conf, sizeof(*ss_conf)))
+		return 0;
+
+	old_conf = dd->ssc_conf;
 	dd->ssc_conf = *ss_conf;
 
-	return 0;
+	/* Disabling SSC does not need to reprogram the DPLL */
+	if (ss_conf->method == CLK_SPREAD_NO) {
+		omap3_noncore_dpll_ssc_program(clk);
+		return 0;
+	}
+
+	/* Not locked: SSC is programmed along with the next rate change */
+	ctrl = ti_clk_ll_ops->clk_readl(&dd->control_reg);
+	if (((ctrl & dd->enable_mask) >> __ffs(dd->enable_mask)) != DPLL_LOCKED)
+		return 0;
+
+	rate = clk_hw_get_rate(hw);
+	clk_hw_init_rate_request(hw, &req, rate);
+	ret = omap2_dpll_determine_rate(hw, &req);
+	if (!ret && req.rate != rate)
+		ret = -EINVAL;
+	if (!ret)
+		ret = omap3_noncore_dpll_set_rate(hw, rate,
+						  clk_hw_get_rate(dd->clk_ref));
+	if (ret) {
+		pr_warn("clock: %s: rate %lu can't be kept with SSC enabled\n",
+			clk_hw_get_name(hw), rate);
+		dd->ssc_conf = old_conf;
+	}
+
+	return ret;
 }
 
 /**
-- 
2.43.0