Re: [PATCH v3 01/12] clk: introduce clk_set_phase function & callback

["Heiko Stübner" <heiko@sntech.de>]

Am Donnerstag, 11. September 2014, 22:18:15 schrieb Maxime Ripard:
> From: Mike Turquette <mturquette@linaro.org>
> 
> A common operation for a clock signal generator is to shift the phase of
> that signal. This patch introduces a new function to the clk.h API to
> dynamically adjust the phase of a clock signal. Additionally this patch
> introduces support for the new function in the common clock framework
> via the .set_phase call back in struct clk_ops.
> 
> Signed-off-by: Mike Turquette <mturquette@linaro.org>
> Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>

This looks nice and would also be very useful for Rockchip SoCs I'm working 
on. And the implementation looks very straightforward.

Reviewed-by: Heiko Stuebner <heiko@sntech.de>

> ---
>  drivers/clk/clk.c            | 85
> +++++++++++++++++++++++++++++++++++++++++--- include/linux/clk-private.h  |
>  1 +
>  include/linux/clk-provider.h |  5 +++
>  include/linux/clk.h          | 29 +++++++++++++++
>  4 files changed, 116 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
> index b76fa69b44cb..d87661af0c72 100644
> --- a/drivers/clk/clk.c
> +++ b/drivers/clk/clk.c
> @@ -117,11 +117,11 @@ static void clk_summary_show_one(struct seq_file *s,
> struct clk *c, int level) if (!c)
>  		return;
> 
> -	seq_printf(s, "%*s%-*s %11d %12d %11lu %10lu\n",
> +	seq_printf(s, "%*s%-*s %11d %12d %11lu %10lu %-3d\n",
>  		   level * 3 + 1, "",
>  		   30 - level * 3, c->name,
>  		   c->enable_count, c->prepare_count, clk_get_rate(c),
> -		   clk_get_accuracy(c));
> +		   clk_get_accuracy(c), clk_get_phase(c));
>  }
> 
>  static void clk_summary_show_subtree(struct seq_file *s, struct clk *c,
> @@ -143,8 +143,8 @@ static int clk_summary_show(struct seq_file *s, void
> *data) struct clk *c;
>  	struct hlist_head **lists = (struct hlist_head **)s->private;
> 
> -	seq_puts(s, "   clock                         enable_cnt  prepare_cnt     
>   rate   accuracy\n"); -	seq_puts(s,
> "--------------------------------------------------------------------------
> ------\n"); +	seq_puts(s, "   clock                         enable_cnt 
> prepare_cnt        rate   accuracy   phase\n"); +	seq_puts(s,
> "--------------------------------------------------------------------------
> --------------\n");
> 
>  	clk_prepare_lock();
> 
> @@ -180,6 +180,7 @@ static void clk_dump_one(struct seq_file *s, struct clk
> *c, int level) seq_printf(s, "\"prepare_count\": %d,", c->prepare_count);
>  	seq_printf(s, "\"rate\": %lu", clk_get_rate(c));
>  	seq_printf(s, "\"accuracy\": %lu", clk_get_accuracy(c));
> +	seq_printf(s, "\"phase\": %d", clk_get_phase(c));
>  }
> 
>  static void clk_dump_subtree(struct seq_file *s, struct clk *c, int level)
> @@ -264,6 +265,11 @@ static int clk_debug_create_one(struct clk *clk, struct
> dentry *pdentry) if (!d)
>  		goto err_out;
> 
> +	d = debugfs_create_u32("clk_phase", S_IRUGO, clk->dentry,
> +			(u32 *)&clk->phase);
> +	if (!d)
> +		goto err_out;
> +
>  	d = debugfs_create_x32("clk_flags", S_IRUGO, clk->dentry,
>  			(u32 *)&clk->flags);
>  	if (!d)
> @@ -1739,6 +1745,77 @@ out:
>  EXPORT_SYMBOL_GPL(clk_set_parent);
> 
>  /**
> + * clk_set_phase - adjust the phase shift of a clock signal
> + * @clk: clock signal source
> + * @degrees: number of degrees the signal is shifted
> + *
> + * Shifts the phase of a clock signal by the specified
> + * degrees. Returns 0 on success, -EERROR otherwise.
> + *
> + * This function makes no distinction about the input or reference
> + * signal that we adjust the clock signal phase against. For example
> + * phase locked-loop clock signal generators we may shift phase with
> + * respect to feedback clock signal input, but for other cases the
> + * clock phase may be shifted with respect to some other, unspecified
> + * signal.
> + *
> + * Additionally the concept of phase shift does not propagate through
> + * the clock tree hierarchy, which sets it apart from clock rates and
> + * clock accuracy. A parent clock phase attribute does not have an
> + * impact on the phase attribute of a child clock.
> + */
> +int clk_set_phase(struct clk *clk, int degrees)
> +{
> +	int ret = 0;
> +
> +	if (!clk)
> +		goto out;
> +
> +	/* sanity check degrees */
> +	degrees %= 360;
> +	if (degrees < 0)
> +		degrees += 360;
> +
> +	clk_prepare_lock();
> +
> +	if (!clk->ops->set_phase)
> +		goto out_unlock;
> +
> +	ret = clk->ops->set_phase(clk->hw, degrees);
> +
> +	if (!ret)
> +		clk->phase = degrees;
> +
> +out_unlock:
> +	clk_prepare_unlock();
> +
> +out:
> +	return ret;
> +}
> +
> +/**
> + * clk_get_phase - return the phase shift of a clock signal
> + * @clk: clock signal source
> + *
> + * Returns the phase shift of a clock node in degrees, otherwise returns
> + * -EERROR.
> + */
> +int clk_get_phase(struct clk *clk)
> +{
> +	int ret = 0;
> +
> +	if (!clk)
> +		goto out;
> +
> +	clk_prepare_lock();
> +	ret = clk->phase;
> +	clk_prepare_unlock();
> +
> +out:
> +	return ret;
> +}
> +
> +/**
>   * __clk_init - initialize the data structures in a struct clk
>   * @dev:	device initializing this clk, placeholder for now
>   * @clk:	clk being initialized
> diff --git a/include/linux/clk-private.h b/include/linux/clk-private.h
> index efbf70b9fd84..845be30be50f 100644
> --- a/include/linux/clk-private.h
> +++ b/include/linux/clk-private.h
> @@ -46,6 +46,7 @@ struct clk {
>  	unsigned int		enable_count;
>  	unsigned int		prepare_count;
>  	unsigned long		accuracy;
> +	int			phase;
>  	struct hlist_head	children;
>  	struct hlist_node	child_node;
>  	unsigned int		notifier_count;
> diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h
> index 411dd7eb2653..201a6195a3eb 100644
> --- a/include/linux/clk-provider.h
> +++ b/include/linux/clk-provider.h
> @@ -129,6 +129,10 @@ struct dentry;
>   *		set then clock accuracy will be initialized to parent accuracy
>   *		or 0 (perfect clock) if clock has no parent.
>   *
> + * @set_phase:	Shift the phase this clock signal in degrees specified
> + *		by the second argument. Valid values for degrees are
> + *		0-359. Return 0 on success, otherwise -EERROR.
> + *
>   * @init:	Perform platform-specific initialization magic.
>   *		This is not not used by any of the basic clock types.
>   *		Please consider other ways of solving initialization problems
> @@ -177,6 +181,7 @@ struct clk_ops {
>  				    unsigned long parent_rate, u8 index);
>  	unsigned long	(*recalc_accuracy)(struct clk_hw *hw,
>  					   unsigned long parent_accuracy);
> +	int		(*set_phase)(struct clk_hw *hw, int degrees);
>  	void		(*init)(struct clk_hw *hw);
>  	int		(*debug_init)(struct clk_hw *hw, struct dentry *dentry);
>  };
> diff --git a/include/linux/clk.h b/include/linux/clk.h
> index fb5e097d8f72..38bdedd3e389 100644
> --- a/include/linux/clk.h
> +++ b/include/linux/clk.h
> @@ -106,6 +106,25 @@ int clk_notifier_unregister(struct clk *clk, struct
> notifier_block *nb); */
>  long clk_get_accuracy(struct clk *clk);
> 
> +/**
> + * clk_set_phase - adjust the phase shift of a clock signal
> + * @clk: clock signal source
> + * @degrees: number of degrees the signal is shifted
> + *
> + * Shifts the phase of a clock signal by the specified degrees. Returns 0
> on + * success, -EERROR otherwise.
> + */
> +int clk_set_phase(struct clk *clk, int degrees);
> +
> +/**
> + * clk_get_phase - return the phase shift of a clock signal
> + * @clk: clock signal source
> + *
> + * Returns the phase shift of a clock node in degrees, otherwise returns
> + * -EERROR.
> + */
> +int clk_get_phase(struct clk *clk);
> +
>  #else
> 
>  static inline long clk_get_accuracy(struct clk *clk)
> @@ -113,6 +132,16 @@ static inline long clk_get_accuracy(struct clk *clk)
>  	return -ENOTSUPP;
>  }
> 
> +static inline long clk_set_phase(struct clk *clk, int phase)
> +{
> +	return -ENOTSUPP;
> +}
> +
> +static inline long clk_get_phase(struct clk *clk)
> +{
> +	return -ENOTSUPP;
> +}
> +
>  #endif
> 
>  /**