linux-kernel - Re: [PATCH v3] clk: si5351: fix .round

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Message-ID: <5528FF0B.80102@gmail.com>
Date:	Sat, 11 Apr 2015 13:01:31 +0200
From:	Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>
To:	Sergej Sawazki <ce3a@....de>, mturquette@...aro.org,
	sboyd@...eaurora.org
CC:	linux-clk@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] clk: si5351: fix .round_rate for multisynth 6-7

On 10.04.2015 21:14, Sergej Sawazki wrote:
> The divider calculation for multisynth 6 and 7 differs from the
> calculation for multisynth 0-5.
>
> For MS6 and MS7, set MSx_P1 directly, MSx_P1 = divide value
> [AN619, p. 6].
>
> Referenced document:
> [AN619] Manually Generating an Si5351 Register Map, Rev. 0.4
>
> Signed-off-by: Sergej Sawazki <ce3a@....de>

Looks good to me now,

Reviewed-by: Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>

Thanks!

> ---
>   drivers/clk/clk-si5351.c | 21 +++++++++++++++++----
>   1 file changed, 17 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/clk/clk-si5351.c b/drivers/clk/clk-si5351.c
> index 44ea107..8e90bdd 100644
> --- a/drivers/clk/clk-si5351.c
> +++ b/drivers/clk/clk-si5351.c
> @@ -552,7 +552,8 @@ static const struct clk_ops si5351_pll_ops = {
>    * MSx_P2[19:0] = 128 * b - c * floor(128 * b/c) = (128*b) mod c
>    * MSx_P3[19:0] = c
>    *
> - * MS[6,7] are integer (P1) divide only, P2 = 0, P3 = 0
> + * MS[6,7] are integer (P1) divide only, P1 = divide value,
> + * P2 and P3 are not applicable
>    *
>    * for 150MHz < fOUT <= 160MHz:
>    *
> @@ -679,6 +680,16 @@ static long si5351_msynth_round_rate(struct clk_hw *hw, unsigned long rate,
>   		c = 1;
>
>   		*parent_rate = a * rate;
> +	} else if (hwdata->num >= 6) {
> +		/* determine the closest integer divider */
> +		a = DIV_ROUND_CLOSEST(*parent_rate, rate);
> +		if (a < SI5351_MULTISYNTH_A_MIN)
> +			a = SI5351_MULTISYNTH_A_MIN;
> +		if (a > SI5351_MULTISYNTH67_A_MAX)
> +			a = SI5351_MULTISYNTH67_A_MAX;
> +
> +		b = 0;
> +		c = 1;
>   	} else {
>   		unsigned long rfrac, denom;
>
> @@ -692,9 +703,7 @@ static long si5351_msynth_round_rate(struct clk_hw *hw, unsigned long rate,
>   		a = *parent_rate / rate;
>   		if (a < SI5351_MULTISYNTH_A_MIN)
>   			a = SI5351_MULTISYNTH_A_MIN;
> -		if (hwdata->num >= 6 && a > SI5351_MULTISYNTH67_A_MAX)
> -			a = SI5351_MULTISYNTH67_A_MAX;
> -		else if (a > SI5351_MULTISYNTH_A_MAX)
> +		if (a > SI5351_MULTISYNTH_A_MAX)
>   			a = SI5351_MULTISYNTH_A_MAX;
>
>   		/* find best approximation for b/c = fVCO mod fOUT */
> @@ -723,6 +732,10 @@ static long si5351_msynth_round_rate(struct clk_hw *hw, unsigned long rate,
>   		hwdata->params.p3 = 1;
>   		hwdata->params.p2 = 0;
>   		hwdata->params.p1 = 0;
> +	} else if (hwdata->num >= 6) {
> +		hwdata->params.p3 = 0;
> +		hwdata->params.p2 = 0;
> +		hwdata->params.p1 = a;
>   	} else {
>   		hwdata->params.p3  = c;
>   		hwdata->params.p2  = (128 * b) % c;
>

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