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Message-ID: <20111011114906.GB27815@b20223-02.ap.freescale.net>
Date: Tue, 11 Oct 2011 19:49:07 +0800
From: Richard Zhao <richard.zhao@...escale.com>
To: Mike Turquette <mturquette@...com>
CC: <linux-kernel@...r.kernel.org>, <paul@...an.com>,
<linaro-dev@...ts.linaro.org>, <linus.walleij@...ricsson.com>,
<patches@...aro.org>, <eric.miao@...aro.org>,
<broonie@...nsource.wolfsonmicro.com>, <magnus.damm@...il.com>,
<amit.kucheria@...aro.org>, <richard.zhao@...aro.org>,
<grant.likely@...retlab.ca>, <dsaxena@...aro.org>,
<arnd.bergmann@...aro.org>, <shawn.guo@...escale.com>,
<skannan@...cinc.com>, <linux@....linux.org.uk>,
<jeremy.kerr@...onical.com>, <tglx@...utronix.de>,
<linux-arm-kernel@...ts.infradead.org>, <sboyd@...inc.com>
Subject: Re: [PATCH v2 2/7] clk: Implement clk_set_rate
On Thu, Sep 22, 2011 at 03:26:57PM -0700, Mike Turquette wrote:
> From: Jeremy Kerr <jeremy.kerr@...onical.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.kerr@...onical.com>
> Signed-off-by: Mark Brown <broonie@...nsource.wolfsonmicro.com>
> Signed-off-by: Mike Turquette <mturquette@...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-kernel@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
>
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