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

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Date:	Thu, 19 Nov 2015 15:18:00 +0100
From:	Belisko Marek <marek.belisko@...il.com>
To:	Jacob Siverskog <jacob@...nage.engineering>
Cc:	Michael Turquette <mturquette@...libre.com>,
	Stephen Boyd <sboyd@...eaurora.org>,
	Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>,
	LKML <linux-kernel@...r.kernel.org>, linux-clk@...r.kernel.org,
	Jens Rudberg <jens@...nage.engineering>
Subject: Re: [PATCH] clk: si5351: Add setup steps

Hi Jacob,

On Thu, Nov 19, 2015 at 2:40 PM, Jacob Siverskog
<jacob@...nage.engineering> 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@...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 */
          ^^^^ 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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