Re: [PATCH] clk: si5351: Add setup steps

From: Belisko Marek
Date: Thu Nov 19 2015 - 09:18:08 EST


Hi Jacob,

On Thu, Nov 19, 2015 at 2:40 PM, Jacob Siverskog
<jacob@xxxxxxxxxxxxxxxxxxx> wrote:
> 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@xxxxxxxxxxxxxxxxxxx>
> Signed-off-by: Jens Rudberg <jens@xxxxxxxxxxxxxxxxxxx>
> ---
> 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 */
^^^^ wrong format of multi line comment, please look at
Documentation/CodingStyle
> + si5351_reg_write(hwdata->drvdata, SI5351_PLL_RESET,
> + SI5351_PLL_RESET_A | SI5351_PLL_RESET_B);
^^^^ according datasheet PLL_RESET_A/B are self clearing bits
valid for Si5351A/C only
so probably we need to add some code for B model
> +
> 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);
> + }
^^^ single line after for statement doesn't need curly
braces (if you run ./scripts/check_patch it will complain)
> +
> /* 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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BR,

marek

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