On Thu, Sep 22, 2011 at 03:26:57PM -0700, Mike Turquette wrote:
> From: Jeremy Kerr <jeremy.k...@canonical.com>
> 
> Implement clk_set_rate by adding a set_rate callback to clk_hw_ops.
> Rates are propagated down the clock tree and recalculated.  Also adds a
> flag for signaling that parents must change rates to achieve the desired
> frequency (upstream propagation).
> 
> TODO:
> Upstream propagation is not yet implemented.
> Device pre-change and post-change notifications are not implemented, but
> are marked up as FIXME comments.
> 
> Signed-off-by: Jeremy Kerr <jeremy.k...@canonical.com>
> Signed-off-by: Mark Brown <broo...@opensource.wolfsonmicro.com>
> Signed-off-by: Mike Turquette <mturque...@ti.com>
> ---
> Changes since v1:
> Remove upstream propagation (for now)
> Rename CLK_SET_RATE_PROPAGATE to CLK_PARENT_RATE_CHANGE
> 
>  drivers/clk/clk.c   |   71 ++++++++++++++++++++++++++++++++++++++++++++++----
>  include/linux/clk.h |   12 ++++++++
>  2 files changed, 77 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
> index 1cd7315..86636c2 100644
> --- a/drivers/clk/clk.c
> +++ b/drivers/clk/clk.c
> @@ -21,6 +21,8 @@ struct clk {
>       unsigned int            enable_count;
>       unsigned int            prepare_count;
>       struct clk              *parent;
> +     struct hlist_head       children;
> +     struct hlist_node       child_node;
>       unsigned long           rate;
>  };
>  
> @@ -176,10 +178,57 @@ long clk_round_rate(struct clk *clk, unsigned long rate)
>  }
>  EXPORT_SYMBOL_GPL(clk_round_rate);
>  
> +/*
> + * clk_recalc_rates - Given a clock (with a recently updated clk->rate),
> + *   notify its children that the rate may need to be recalculated, using
> + *   ops->recalc_rate().
> + */
> +static void clk_recalc_rates(struct clk *clk)
> +{
> +     struct hlist_node *tmp;
> +     struct clk *child;
> +
> +     if (clk->ops->recalc_rate)
> +             clk->rate = clk->ops->recalc_rate(clk->hw);
pass it parent rate if recalc_rate is NULL?
> +
> +     /* FIXME add post-rate change notification here */
> +
> +     hlist_for_each_entry(child, tmp, &clk->children, child_node)
> +             clk_recalc_rates(child);
> +}
> +
>  int clk_set_rate(struct clk *clk, unsigned long rate)
>  {
> -     /* not yet implemented */
> -     return -ENOSYS;
> +     unsigned long parent_rate, new_rate;
> +     int ret = 0;
> +
> +     if (!clk->ops->set_rate)
> +             return -ENOSYS;
> +
> +     new_rate = rate;
> +
> +     /* prevent racing with updates to the clock topology */
> +     mutex_lock(&prepare_lock);
> +
> +     /* FIXME add pre-rate change notification here */
> +
> +     ret = clk->ops->set_rate(clk->hw, new_rate, &parent_rate);
> +
> +     /* FIXME ignores CLK_PARENT_RATE_CHANGE */
why do we need upstream propagate? for cascaded dividers? It may effect
parent's other children.
Does rate have to be rate returned by round_rate? I guess we can
accept none exact rate.

Thanks
Richard
> +     if (ret < 0)
> +             /* FIXME add rate change abort notification here */
> +             goto out;
> +
> +     /*
> +      * If successful recalculate the rates of the clock, including
> +      * children.
> +      */
> +     clk_recalc_rates(clk);
> +
> +out:
> +     mutex_unlock(&prepare_lock);
> +
> +     return ret;
>  }
>  EXPORT_SYMBOL_GPL(clk_set_rate);
>  
> @@ -216,16 +265,26 @@ struct clk *clk_register(const struct clk_hw_ops *ops, 
> struct clk_hw *hw,
>       clk->hw = hw;
>       hw->clk = clk;
>  
> -     /* Query the hardware for parent and initial rate */
> +     /*
> +      * Query the hardware for parent and initial rate. We may alter
> +      * the clock topology, making this clock available from the parent's
> +      * children list. So, we need to protect against concurrent
> +      * accesses through set_rate
> +      */
> +     mutex_lock(&prepare_lock);
>  
> -     if (clk->ops->get_parent)
> -             /* We don't to lock against prepare/enable here, as
> -              * the clock is not yet accessible from anywhere */
> +     if (clk->ops->get_parent) {
>               clk->parent = clk->ops->get_parent(clk->hw);
> +             if (clk->parent)
> +                     hlist_add_head(&clk->child_node,
> +                                     &clk->parent->children);
> +     }
>  
>       if (clk->ops->recalc_rate)
>               clk->rate = clk->ops->recalc_rate(clk->hw);
>  
> +     mutex_unlock(&prepare_lock);
> +
>  
>       return clk;
>  }
> diff --git a/include/linux/clk.h b/include/linux/clk.h
> index d6ae10b..0d2cd5e 100644
> --- a/include/linux/clk.h
> +++ b/include/linux/clk.h
> @@ -58,6 +58,12 @@ struct clk_hw {
>   *           parent. Currently only called when the clock is first
>   *           registered.
>   *
> + * @set_rate Change the rate of this clock. If this callback returns
> + *           CLK_SET_RATE_PROPAGATE, the rate change will be propagated to
> + *           the parent clock (which may propagate again). The requested
> + *           rate of the parent is passed back from the callback in the
> + *           second 'unsigned long *' argument.
> + *
>   * The clk_enable/clk_disable and clk_prepare/clk_unprepare pairs allow
>   * implementations to split any work between atomic (enable) and sleepable
>   * (prepare) contexts.  If a clock requires sleeping code to be turned on, 
> this
> @@ -76,9 +82,15 @@ struct clk_hw_ops {
>       void            (*disable)(struct clk_hw *);
>       unsigned long   (*recalc_rate)(struct clk_hw *);
>       long            (*round_rate)(struct clk_hw *, unsigned long);
> +     int             (*set_rate)(struct clk_hw *,
> +                                     unsigned long, unsigned long *);
>       struct clk *    (*get_parent)(struct clk_hw *);
>  };
>  
> +enum {
> +     CLK_PARENT_RATE_CHANGE = 1,
> +};
> +
>  /**
>   * clk_prepare - prepare clock for atomic enabling.
>   *
> -- 
> 1.7.4.1
> 
> 
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-ker...@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
> 


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