Re: [PATCH v3 03/12] clk: Add a function to retrieve phase

["Heiko Stübner" <heiko@sntech.de>]

Am Donnerstag, 11. September 2014, 22:18:17 schrieb Maxime Ripard:
> The current phase API doesn't look into the actual hardware to get the phase
> value, but will rather get it from a variable only set by the set_phase
> function.
> 
> This will cause issue when the client driver will never call the set_phase
> function, where we can end up having a reported phase that will not match
> what the hardware has been programmed to by the bootloader or what phase is
> programmed out of reset.
> 
> Add a new get_phase function for the drivers to implement so that we can get
> this value.
> 
> Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>

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

> ---
>  drivers/clk/clk.c            | 10 ++++++++++
>  include/linux/clk-provider.h |  5 +++++
>  2 files changed, 15 insertions(+)
> 
> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
> index d87661af0c72..113d75db371d 100644
> --- a/drivers/clk/clk.c
> +++ b/drivers/clk/clk.c
> @@ -1934,6 +1934,16 @@ int __clk_init(struct device *dev, struct clk *clk)
>  		clk->accuracy = 0;
> 
>  	/*
> +	 * Set clk's phase.
> +	 * Since a phase is by definition relative to its parent, just
> +	 * query the current clock phase, or just assume it's in phase.
> +	 */
> +	if (clk->ops->get_phase)
> +		clk->phase = clk->ops->get_phase(clk->hw);
> +	else
> +		clk->phase = 0;
> +
> +	/*
>  	 * Set clk's rate.  The preferred method is to use .recalc_rate.  For
>  	 * simple clocks and lazy developers the default fallback is to use the
>  	 * parent's rate.  If a clock doesn't have a parent (or is orphaned)
> diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h
> index 69b20d4c1e1a..abec961092a7 100644
> --- a/include/linux/clk-provider.h
> +++ b/include/linux/clk-provider.h
> @@ -130,6 +130,10 @@ struct dentry;
>   *		set then clock accuracy will be initialized to parent accuracy
>   *		or 0 (perfect clock) if clock has no parent.
>   *
> + * @get_phase:	Queries the hardware to get the current phase of a clock.
> + *		Returned values are 0-359 degrees on success, negative
> + *		error codes on failure.
> + *
>   * @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.
> @@ -182,6 +186,7 @@ struct clk_ops {
>  				    unsigned long parent_rate, u8 index);
>  	unsigned long	(*recalc_accuracy)(struct clk_hw *hw,
>  					   unsigned long parent_accuracy);
> +	int		(*get_phase)(struct clk_hw *hw);
>  	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);