Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1701208 > unrolled thread

[PATCH 1/2] clk: fractional-divider: allow overriding of approximation

Back to article view | Back to linux.kernel

This discussion starts older than the indexed window; earlier articles aren't shown. The article labeled Started by below is the oldest one visible, not the original post.

Contents

  [PATCH 1/2] clk: fractional-divider: allow overriding of approximation Heiko Stuebner <heiko@sntech.de> - 2017-08-01 18:30 +0200
    Re: [PATCH 1/2] clk: fractional-divider: allow overriding of approximation Elaine Zhang <zhangqing@rock-chips.com> - 2017-08-02 05:50 +0200
    Re: [PATCH 1/2] clk: fractional-divider: allow overriding of  approximation Stephen Boyd <sboyd@codeaurora.org> - 2017-08-08 01:10 +0200
    Re: [PATCH 1/2] clk: fractional-divider: allow overriding of approximation Heiko Stuebner <heiko@sntech.de> - 2017-08-08 18:00 +0200

#1701208 — [PATCH 1/2] clk: fractional-divider: allow overriding of approximation

From: Elaine Zhang <zhangqing@rock-chips.com>

Fractional dividers may have special requirements concerning numerator
and denominator selection that differ from just getting the best
approximation.

For example on Rockchip socs the denominator must be at least 20 times
larger than the numerator to generate precise clock frequencies.

Therefore add the ability to provide custom approximation functions.

Signed-off-by: Elaine Zhang <zhangqing@rock-chips.com>
---
 drivers/clk/clk-fractional-divider.c | 28 ++++++++++++++++++++--------
 include/linux/clk-provider.h         |  3 +++
 2 files changed, 23 insertions(+), 8 deletions(-)

diff --git a/drivers/clk/clk-fractional-divider.c b/drivers/clk/clk-fractional-divider.c
index aab904618eb6..fdf625fb10fa 100644
--- a/drivers/clk/clk-fractional-divider.c
+++ b/drivers/clk/clk-fractional-divider.c
@@ -49,16 +49,12 @@ static unsigned long clk_fd_recalc_rate(struct clk_hw *hw,
 	return ret;
 }
 
-static long clk_fd_round_rate(struct clk_hw *hw, unsigned long rate,
-			      unsigned long *parent_rate)
+static void clk_fd_general_approximation(struct clk_hw *hw, unsigned long rate,
+					 unsigned long *parent_rate,
+					 unsigned long *m, unsigned long *n)
 {
 	struct clk_fractional_divider *fd = to_clk_fd(hw);
 	unsigned long scale;
-	unsigned long m, n;
-	u64 ret;
-
-	if (!rate || rate >= *parent_rate)
-		return *parent_rate;
 
 	/*
 	 * Get rate closer to *parent_rate to guarantee there is no overflow
@@ -71,7 +67,23 @@ static long clk_fd_round_rate(struct clk_hw *hw, unsigned long rate,
 
 	rational_best_approximation(rate, *parent_rate,
 			GENMASK(fd->mwidth - 1, 0), GENMASK(fd->nwidth - 1, 0),
-			&m, &n);
+			m, n);
+}
+
+static long clk_fd_round_rate(struct clk_hw *hw, unsigned long rate,
+			      unsigned long *parent_rate)
+{
+	struct clk_fractional_divider *fd = to_clk_fd(hw);
+	unsigned long m, n;
+	u64 ret;
+
+	if (!rate || rate >= *parent_rate)
+		return *parent_rate;
+
+	if (fd->approximation)
+		fd->approximation(hw, rate, parent_rate, &m, &n);
+	else
+		clk_fd_general_approximation(hw, rate, parent_rate, &m, &n);
 
 	ret = (u64)*parent_rate * m;
 	do_div(ret, n);
diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h
index c59c62571e4f..1fc113fbf955 100644
--- a/include/linux/clk-provider.h
+++ b/include/linux/clk-provider.h
@@ -565,6 +565,9 @@ struct clk_fractional_divider {
 	u8		nwidth;
 	u32		nmask;
 	u8		flags;
+	void		(*approximation)(struct clk_hw *hw,
+				unsigned long rate, unsigned long *parent_rate,
+				unsigned long *m, unsigned long *n);
 	spinlock_t	*lock;
 };
 
-- 
2.11.0

[toc] | [next] | [standalone]

#1701684

hi,heiko:

This a good solution.And I tested it on RK SOCs.It's work well.

On 08/02/2017 12:21 AM, Heiko Stuebner wrote:
> From: Elaine Zhang <zhangqing@rock-chips.com>
>
> Fractional dividers may have special requirements concerning numerator
> and denominator selection that differ from just getting the best
> approximation.
>
> For example on Rockchip socs the denominator must be at least 20 times
> larger than the numerator to generate precise clock frequencies.
>
> Therefore add the ability to provide custom approximation functions.
>
> Signed-off-by: Elaine Zhang <zhangqing@rock-chips.com>
> ---
>   drivers/clk/clk-fractional-divider.c | 28 ++++++++++++++++++++--------
>   include/linux/clk-provider.h         |  3 +++
>   2 files changed, 23 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/clk/clk-fractional-divider.c b/drivers/clk/clk-fractional-divider.c
> index aab904618eb6..fdf625fb10fa 100644
> --- a/drivers/clk/clk-fractional-divider.c
> +++ b/drivers/clk/clk-fractional-divider.c
> @@ -49,16 +49,12 @@ static unsigned long clk_fd_recalc_rate(struct clk_hw *hw,
>   	return ret;
>   }
>
> -static long clk_fd_round_rate(struct clk_hw *hw, unsigned long rate,
> -			      unsigned long *parent_rate)
> +static void clk_fd_general_approximation(struct clk_hw *hw, unsigned long rate,
> +					 unsigned long *parent_rate,
> +					 unsigned long *m, unsigned long *n)
>   {
>   	struct clk_fractional_divider *fd = to_clk_fd(hw);
>   	unsigned long scale;
> -	unsigned long m, n;
> -	u64 ret;
> -
> -	if (!rate || rate >= *parent_rate)
> -		return *parent_rate;
>
>   	/*
>   	 * Get rate closer to *parent_rate to guarantee there is no overflow
> @@ -71,7 +67,23 @@ static long clk_fd_round_rate(struct clk_hw *hw, unsigned long rate,
>
>   	rational_best_approximation(rate, *parent_rate,
>   			GENMASK(fd->mwidth - 1, 0), GENMASK(fd->nwidth - 1, 0),
> -			&m, &n);
> +			m, n);
> +}
> +
> +static long clk_fd_round_rate(struct clk_hw *hw, unsigned long rate,
> +			      unsigned long *parent_rate)
> +{
> +	struct clk_fractional_divider *fd = to_clk_fd(hw);
> +	unsigned long m, n;
> +	u64 ret;
> +
> +	if (!rate || rate >= *parent_rate)
> +		return *parent_rate;
> +
> +	if (fd->approximation)
> +		fd->approximation(hw, rate, parent_rate, &m, &n);
> +	else
> +		clk_fd_general_approximation(hw, rate, parent_rate, &m, &n);
>
>   	ret = (u64)*parent_rate * m;
>   	do_div(ret, n);
> diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h
> index c59c62571e4f..1fc113fbf955 100644
> --- a/include/linux/clk-provider.h
> +++ b/include/linux/clk-provider.h
> @@ -565,6 +565,9 @@ struct clk_fractional_divider {
>   	u8		nwidth;
>   	u32		nmask;
>   	u8		flags;
> +	void		(*approximation)(struct clk_hw *hw,
> +				unsigned long rate, unsigned long *parent_rate,
> +				unsigned long *m, unsigned long *n);
>   	spinlock_t	*lock;
>   };
>
>
Tested-by: Elaine Zhang <zhangqing@rock-chips.com>

[toc] | [prev] | [next] | [standalone]

#1705911 — Re: [PATCH 1/2] clk: fractional-divider: allow overriding of approximation

On 08/01, Heiko Stuebner wrote:
> From: Elaine Zhang <zhangqing@rock-chips.com>
> 
> Fractional dividers may have special requirements concerning numerator
> and denominator selection that differ from just getting the best
> approximation.
> 
> For example on Rockchip socs the denominator must be at least 20 times
> larger than the numerator to generate precise clock frequencies.
> 
> Therefore add the ability to provide custom approximation functions.
> 
> Signed-off-by: Elaine Zhang <zhangqing@rock-chips.com>
> ---

Acked-by: Stephen Boyd <sboyd@codeaurora.org>

-- 
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
a Linux Foundation Collaborative Project

[toc] | [prev] | [next] | [standalone]

#1706696

Am Dienstag, 1. August 2017, 18:21:22 CEST schrieb Heiko Stuebner:
> From: Elaine Zhang <zhangqing@rock-chips.com>
> 
> Fractional dividers may have special requirements concerning numerator
> and denominator selection that differ from just getting the best
> approximation.
> 
> For example on Rockchip socs the denominator must be at least 20 times
> larger than the numerator to generate precise clock frequencies.
> 
> Therefore add the ability to provide custom approximation functions.
> 
> Signed-off-by: Elaine Zhang <zhangqing@rock-chips.com>

applied for 4.14 with Stephen's Ack


Heiko

[toc] | [prev] | [standalone]

Back to top | Article view | linux.kernel

csiph-web