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

[Dario Binacchi <dario.binacchi@amarulasolutions.com>]

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>

---

 drivers/clk/ti/dpll3xxx.c | 49 ++++++++++++++++++++++++++++++++++-----
 1 file changed, 43 insertions(+), 6 deletions(-)

diff --git a/drivers/clk/ti/dpll3xxx.c b/drivers/clk/ti/dpll3xxx.c
index 634fe0a1f9fd..c181bba2792d 100644
--- a/drivers/clk/ti/dpll3xxx.c
+++ b/drivers/clk/ti/dpll3xxx.c
@@ -690,17 +690,26 @@ 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
+ * applies it right away. The clock framework does not call set_rate()
+ * when the rate is unchanged, so the current rate is rounded again and
+ * the DPLL is reprogrammed. If the DPLL is in bypass the configuration is
+ * applied at the next rate change. Setting again the current
+ * configuration is a no-op, so that the DPLL is not relocked for nothing
+ * (e.g. of_clk_set_defaults() runs twice for CLK_OF_DECLARE providers
+ * that register themselves with of_clk_add_provider()). 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;
+	struct clk_spread_spectrum old_conf;
+	struct clk_rate_request req;
+	unsigned long rate;
+	int ret;
 
 	if (!dd || !dd->ssc_enable_mask)
 		return -EOPNOTSUPP;
@@ -718,9 +727,37 @@ 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;
+	/* In bypass: SSC is programmed along with the next rate change */
+	if (clk_hw_get_parent(hw) != dd->clk_ref)
+		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;
+	}
+
+	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