[v3,06/10] clk: add clk_set_rate_protect

Commit Message

Jerome Brunet June 12, 2017, 7:44 p.m. UTC

clk_set_rate_protect is a combination of clk_set_rate and clk_rate_protect
within a critical section. In case where several protecting consumers
compete to set the rate of the same provider, it provides a way to make
sure that at least one of them will be satisfied before the resource is
locked.

This is to avoid the unlikely situation where several consumers protect a
clock provider and none actually get a rate it can work with.

Signed-off-by: Jerome Brunet <[e-mail]>
---
 drivers/clk/clk.c   | 45 +++++++++++++++++++++++++++++++++++++++++++++
 include/linux/clk.h | 14 ++++++++++++++
 2 files changed, 59 insertions(+)

Comments

Stephen Boyd July 26, 2017, 12:59 a.m. UTC | #1

On 06/12, Jerome Brunet wrote:
> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
> index d688b8f59a59..d91236e70a04 100644
> --- a/drivers/clk/clk.c
> +++ b/drivers/clk/clk.c
> @@ -1809,6 +1809,51 @@ int clk_set_rate(struct clk *clk, unsigned long rate)
>  EXPORT_SYMBOL_GPL(clk_set_rate);
>  
>  /**
> + * clk_set_rate_protect - specify a new rate and protect it
> + * @clk: the clk whose rate is being changed
> + * @rate: the new rate for clk
> + *
> + * This is a combination of clk_set_rate and clk_rate_protect within

s/clk_set_rate/clk_set_rate()/
s/clk_rate_protect/clk_rate_protect()/

> + * a critical section
> + *
> + * This can be used initially to ensure that at least 1 consumers is

s/consumers/consumer/

> + * statisfied when several protecting consummers are competing for the

s/consummers/consumers/

> + * same clock provider.
> + *
> + * The protection is not applied if setting the rate failed.
> + *
> + * Returns 0 on success, -EERROR otherwise.
> + */
> +int clk_set_rate_protect(struct clk *clk, unsigned long rate)
> +{
> +	int ret;
> +
> +	if (!clk)
> +		return 0;
> +
> +	/* prevent racing with updates to the clock topology */
> +	clk_prepare_lock();
> +
> +	/*
> +	 * The temporary protection removal is not here, on purpose
> +	 * This function is meant to be used in instead of clk_rate_protect,

s/in//

> +	 * so before the consumer code path protect the clock provider
> +	 */
> +
> +	ret = clk_core_set_rate_nolock(clk->core, rate);
> +

Drop newline please.

> +	if (!ret) {
> +		clk_core_rate_protect(clk->core);
> +		clk->protect_count++;
> +	}
> +
> +	clk_prepare_unlock();
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(clk_set_rate_protect);
> +
> +/**
>   * clk_set_rate_range - set a rate range for a clock source
>   * @clk: clock source
>   * @min: desired minimum clock rate in Hz, inclusive

Patch

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index d688b8f59a59..d91236e70a04 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -1809,6 +1809,51 @@  int clk_set_rate(struct clk *clk, unsigned long rate)
 EXPORT_SYMBOL_GPL(clk_set_rate);
 
 /**
+ * clk_set_rate_protect - specify a new rate and protect it
+ * @clk: the clk whose rate is being changed
+ * @rate: the new rate for clk
+ *
+ * This is a combination of clk_set_rate and clk_rate_protect within
+ * a critical section
+ *
+ * This can be used initially to ensure that at least 1 consumers is
+ * statisfied when several protecting consummers are competing for the
+ * same clock provider.
+ *
+ * The protection is not applied if setting the rate failed.
+ *
+ * Returns 0 on success, -EERROR otherwise.
+ */
+int clk_set_rate_protect(struct clk *clk, unsigned long rate)
+{
+	int ret;
+
+	if (!clk)
+		return 0;
+
+	/* prevent racing with updates to the clock topology */
+	clk_prepare_lock();
+
+	/*
+	 * The temporary protection removal is not here, on purpose
+	 * This function is meant to be used in instead of clk_rate_protect,
+	 * so before the consumer code path protect the clock provider
+	 */
+
+	ret = clk_core_set_rate_nolock(clk->core, rate);
+
+	if (!ret) {
+		clk_core_rate_protect(clk->core);
+		clk->protect_count++;
+	}
+
+	clk_prepare_unlock();
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(clk_set_rate_protect);
+
+/**
  * clk_set_rate_range - set a rate range for a clock source
  * @clk: clock source
  * @min: desired minimum clock rate in Hz, inclusive
diff --git a/include/linux/clk.h b/include/linux/clk.h
index b60c36f2e6b0..7a01b32f7029 100644
--- a/include/linux/clk.h
+++ b/include/linux/clk.h
@@ -497,6 +497,15 @@  long clk_round_rate(struct clk *clk, unsigned long rate);
 int clk_set_rate(struct clk *clk, unsigned long rate);
 
 /**
+ * clk_set_rate_protect - set and protect the clock rate for a clock source
+ * @clk: clock source
+ * @rate: desired clock rate in Hz
+ *
+ * Returns success (0) or negative errno.
+ */
+int clk_set_rate_protect(struct clk *clk, unsigned long rate);
+
+/**
  * clk_has_parent - check if a clock is a possible parent for another
  * @clk: clock source
  * @parent: parent clock source
@@ -638,6 +647,11 @@  static inline int clk_set_rate(struct clk *clk, unsigned long rate)
 	return 0;
 }
 
+static inline int clk_set_rate_protect(struct clk *clk, unsigned long rate)
+{
+	return 0;
+}
+
 static inline long clk_round_rate(struct clk *clk, unsigned long rate)
 {
 	return 0;