[PATCH] clk: si5351: Add gapless tuning for SI5351 PLL

[Michal Bachraty]

For gapless tuning, there is no need for PLL reset and clkout power-down
when tuning output. "silabs,gapless-tuning" parameter enables gapless tuning
for specific clock output.

Signed-off-by: Michal Bachraty <michal.bachraty at streamunlimited.com>
---
 .../devicetree/bindings/clock/silabs,si5351.txt    |    2 ++
 drivers/clk/clk-si5351.c                           |   27 +++++++++++++++++---
 2 files changed, 25 insertions(+), 4 deletions(-)

diff --git a/Documentation/devicetree/bindings/clock/silabs,si5351.txt b/Documentation/devicetree/bindings/clock/silabs,si5351.txt
index cc37465..e16ab2b 100644
--- a/Documentation/devicetree/bindings/clock/silabs,si5351.txt
+++ b/Documentation/devicetree/bindings/clock/silabs,si5351.txt
@@ -44,6 +44,8 @@ Optional child node properties:
 - silabs,multisynth-source: source pll A(0) or B(1) of corresponding multisynth
   divider.
 - silabs,pll-master: boolean, multisynth can change pll frequency.
+- silabs,gapless-tuning: boolean, enable gapless (glitch-free) tuning. Depends on
+  "silabs,multisynth-source" parameter.
 
 ==Example==
 
diff --git a/drivers/clk/clk-si5351.c b/drivers/clk/clk-si5351.c
index e259cec..d3933a9 100644
--- a/drivers/clk/clk-si5351.c
+++ b/drivers/clk/clk-si5351.c
@@ -54,6 +54,7 @@ struct si5351_hw_data {
 	struct si5351_driver_data	*drvdata;
 	struct si5351_parameters	params;
 	unsigned char			num;
+	unsigned char			gapless_tuning;
 };
 
 struct si5351_driver_data {
@@ -526,8 +527,10 @@ static int si5351_pll_set_rate(struct clk_hw *hw, unsigned long rate,
 		(hwdata->params.p2 == 0) ? SI5351_CLK_INTEGER_MODE : 0);
 
 	/* reset pll */
-	val = (hwdata->num == 0) ? SI5351_PLL_RESET_A : SI5351_PLL_RESET_B;
-	si5351_set_bits(hwdata->drvdata, SI5351_PLL_RESET, val, val);
+	if (!hwdata->gapless_tuning) {
+		val = (hwdata->num == 0) ? SI5351_PLL_RESET_A : SI5351_PLL_RESET_B;
+		si5351_set_bits(hwdata->drvdata, SI5351_PLL_RESET, val, val);
+	}
 
 	dev_dbg(&hwdata->drvdata->client->dev,
 		"%s - %s: p1 = %lu, p2 = %lu, p3 = %lu, parent_rate = %lu, rate = %lu\n",
@@ -1064,8 +1067,9 @@ static int si5351_clkout_set_rate(struct clk_hw *hw, unsigned long rate,
 	} while (1);
 
 	/* powerdown clkout */
-	si5351_set_bits(hwdata->drvdata, SI5351_CLK0_CTRL + hwdata->num,
-			SI5351_CLK_POWERDOWN, SI5351_CLK_POWERDOWN);
+	if (!hwdata->gapless_tuning)
+		si5351_set_bits(hwdata->drvdata, SI5351_CLK0_CTRL + hwdata->num,
+				SI5351_CLK_POWERDOWN, SI5351_CLK_POWERDOWN);
 
 	/* write output divider */
 	switch (hwdata->num) {
@@ -1117,6 +1121,7 @@ static void si5351_dt_setup(
 	struct property *prop;
 	const __be32 *p;
 	unsigned int num, val;
+	int pll = -1;
 
 	if (np == NULL)
 		return;
@@ -1167,6 +1172,8 @@ static void si5351_dt_setup(
 				dev_warn(&client->dev,
 					 "unable to reparent multisynth %d to %d\n",
 					 num, val);
+			else
+				pll = val;
 		}
 
 		if (!of_property_read_u32(np, "silabs,clock-source", &val)) {
@@ -1178,6 +1185,15 @@ static void si5351_dt_setup(
 
 		if (!of_property_read_u32(np, "clock-frequency", &val))
 			clk_set_rate(drvdata->onecell.clks[num], val);
+
+		if (of_property_read_bool(np, "silabs,gapless-tuning")) {
+			if (pll >= 0) {
+				drvdata->clkout[num].gapless_tuning = 1;
+				drvdata->pll[pll].gapless_tuning = 1;
+			} else
+				dev_warn(&client->dev,
+					"unable to set gapless tuning");
+		}
 	}
 }
 
@@ -1294,6 +1310,7 @@ static int si5351_i2c_probe(struct i2c_client *client,
 	drvdata->pll[0].num = 0;
 	drvdata->pll[0].drvdata = drvdata;
 	drvdata->pll[0].hw.init = &init;
+	drvdata->pll[0].gapless_tuning = 0;
 	memset(&init, 0, sizeof(init));
 	init.name = si5351_pll_names[0];
 	init.ops = &si5351_pll_ops;
@@ -1310,6 +1327,7 @@ static int si5351_i2c_probe(struct i2c_client *client,
 	drvdata->pll[1].num = 1;
 	drvdata->pll[1].drvdata = drvdata;
 	drvdata->pll[1].hw.init = &init;
+	drvdata->pll[1].gapless_tuning = 0;
 	memset(&init, 0, sizeof(init));
 	if (drvdata->variant == SI5351_VARIANT_B) {
 		init.name = si5351_pll_names[2];
@@ -1380,6 +1398,7 @@ static int si5351_i2c_probe(struct i2c_client *client,
 		drvdata->clkout[n].num = n;
 		drvdata->clkout[n].drvdata = drvdata;
 		drvdata->clkout[n].hw.init = &init;
+		drvdata->clkout[n].gapless_tuning = 0;
 		memset(&init, 0, sizeof(init));
 		init.name = si5351_clkout_names[n];
 		init.ops = &si5351_clkout_ops;
-- 
1.7.9.5