linux-kernel - [PATCH] clk: si5351: Add setup steps

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Message-Id: <1447940410-9728-1-git-send-email-jacob@teenage.engineering>
Date:	Thu, 19 Nov 2015 14:40:10 +0100
From:	Jacob Siverskog <jacob@...nage.engineering>
To:	Michael Turquette <mturquette@...libre.com>,
	Stephen Boyd <sboyd@...eaurora.org>,
	Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>,
	linux-kernel@...r.kernel.org, linux-clk@...r.kernel.org
Cc:	Jacob Siverskog <jacob@...nage.engineering>,
	Jens Rudberg <jens@...nage.engineering>
Subject: [PATCH] clk: si5351: Add setup steps

This is according to figure 12 ("I2C Programming Procedure") in
"Si5351A/B/C Data Sheet"
(https://www.silabs.com/Support%20Documents/TechnicalDocs/Si5351-B.pdf).

Without the PLL soft reset, we were unable to get three outputs
working at the same time.

According to Silicon Labs support, performing PLL soft reset will only
be noticable if the PLL parameters have been changed.

Signed-off-by: Jacob Siverskog <jacob@...nage.engineering>
Signed-off-by: Jens Rudberg <jens@...nage.engineering>
---
 drivers/clk/clk-si5351.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/drivers/clk/clk-si5351.c b/drivers/clk/clk-si5351.c
index e346b22..110de35 100644
--- a/drivers/clk/clk-si5351.c
+++ b/drivers/clk/clk-si5351.c
@@ -1091,6 +1091,11 @@ static int si5351_clkout_set_rate(struct clk_hw *hw, unsigned long rate,
 	si5351_set_bits(hwdata->drvdata, SI5351_CLK0_CTRL + hwdata->num,
 			SI5351_CLK_POWERDOWN, 0);
 
+	/* do a pll soft reset on both plls, needed in some cases to get all
+	 * outputs running */
+	si5351_reg_write(hwdata->drvdata, SI5351_PLL_RESET,
+			 SI5351_PLL_RESET_A | SI5351_PLL_RESET_B);
+
 	dev_dbg(&hwdata->drvdata->client->dev,
 		"%s - %s: rdiv = %u, parent_rate = %lu, rate = %lu\n",
 		__func__, clk_hw_get_name(hw), (1 << rdiv),
@@ -1359,6 +1364,14 @@ static int si5351_i2c_probe(struct i2c_client *client,
 		return PTR_ERR(drvdata->regmap);
 	}
 
+	/* Disable outputs */
+	si5351_reg_write(drvdata, SI5351_OUTPUT_ENABLE_CTRL, 0xff);
+
+	/* Power down all output drivers */
+	for (n = 0; n < 8; n++) {
+		si5351_reg_write(drvdata, SI5351_CLK0_CTRL + n, 0x80);
+	}
+
 	/* Disable interrupts */
 	si5351_reg_write(drvdata, SI5351_INTERRUPT_MASK, 0xf0);
 	/* Ensure pll select is on XTAL for Si5351A/B */
-- 
2.6.3

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