[PATCH v2 3/7] omap: clock: Add allow_idle/deny_idle support in clkops

[Paul Walmsley]

Hi Rajendra

On Thu, 10 Feb 2011, Rajendra Nayak wrote:

> diff --git a/arch/arm/plat-omap/clock.c b/arch/arm/plat-omap/clock.c
> index fc62fb5..6889c5a 100644
> --- a/arch/arm/plat-omap/clock.c
> +++ b/arch/arm/plat-omap/clock.c
> @@ -335,6 +335,32 @@ struct clk *omap_clk_get_by_name(const char *name)
>  	return ret;
>  }
>
> +void omap_clk_enable_autoidle(void)
> +{
> +	struct clk *c;
> +
> +	mutex_lock(&clocks_mutex);

With the current OMAP clock code, it isn't sufficient to use a mutex here.  
Your underlying functions have to read, modify, and write a register that 
is also touched by clock functions like clk_set_rate(), which take the 
clockfw spinlock and not the mutex.  This is potentially racy and could 
result in inconsistencies between the internal clock tree data and the 
hardware settings.

While it is true that these functions are currently only called during PM 
init, I'd rather not commit code that is subject to known races into the 
tree.

So, before applying this patch, the mutexes have been converted into 
spinlocks.  I would appreciate it if you could help test this.  Updated 
patch follows, which has been queued for 2.6.39 as part of the 
'clk_autoidle_a_2.6.39' branch of git://git.pwsan.com/linux-2.6.


- Paul

From: Rajendra Nayak <rnayak at ti.com>
Date: Thu, 10 Feb 2011 14:46:36 +0530
Subject: [PATCH] omap: clock: Add allow_idle/deny_idle support in clkops

On OMAP various clock nodes (dpll's, mx post dividers, interface clocks)
support hardware level autogating which can be controlled from
software.
Support such functionality by adding two new function pointer
allow_idle and deny_idle in the clkops structure.

These function pointers can be populated for any clock
node which supports hardware level autogating.

Also add 2 new functions (omap_clk_enable_auotidle and
omap_clk_disable_autoidle) which can be called from
architecture specific PM core code, if hardware level
autogating (for all supported clock nodes) is to be
enabled or disabled.

Signed-off-by: Rajendra Nayak <rnayak at ti.com>
[paul at pwsan.com: use spinlock rather than mutex due to race]
Signed-off-by: Paul Walmsley <paul at pwsan.com>
---
 arch/arm/plat-omap/clock.c              |   28 ++++++++++++++++++++++++++++
 arch/arm/plat-omap/include/plat/clock.h |    6 ++++++
 2 files changed, 34 insertions(+), 0 deletions(-)

diff --git a/arch/arm/plat-omap/clock.c b/arch/arm/plat-omap/clock.c
index fc62fb5..0cdac8d 100644
--- a/arch/arm/plat-omap/clock.c
+++ b/arch/arm/plat-omap/clock.c
@@ -335,6 +335,34 @@ struct clk *omap_clk_get_by_name(const char *name)
 	return ret;
 }
 
+void omap_clk_enable_autoidle(void)
+{
+	struct clk *c;
+	unsigned long flags;
+
+	spin_lock_irqsave(&clockfw_lock, flags);
+
+	list_for_each_entry(c, &clocks, node)
+		if (c->ops->allow_idle)
+			c->ops->allow_idle(c);
+
+	spin_lock_irqrestore(&clockfw_lock, flags);
+}
+
+void omap_clk_disable_autoidle(void)
+{
+	struct clk *c;
+	unsigned long flags;
+
+	spin_lock_irqsave(&clockfw_lock, flags);
+
+	list_for_each_entry(c, &clocks, node)
+		if (c->ops->deny_idle)
+			c->ops->deny_idle(c);
+
+	spin_lock_irqrestore(&clockfw_lock, flags);
+}
+
 /*
  * Low level helpers
  */
diff --git a/arch/arm/plat-omap/include/plat/clock.h b/arch/arm/plat-omap/include/plat/clock.h
index 8eb0ada..167f1e0f 100644
--- a/arch/arm/plat-omap/include/plat/clock.h
+++ b/arch/arm/plat-omap/include/plat/clock.h
@@ -25,6 +25,8 @@ struct clockdomain;
  * @disable: fn ptr that enables the current clock in hardware
  * @find_idlest: function returning the IDLEST register for the clock's IP blk
  * @find_companion: function returning the "companion" clk reg for the clock
+ * @allow_idle: fn ptr that enables autoidle for the current clock in hardware
+ * @deny_idle: fn ptr that disables autoidle for the current clock in hardware
  *
  * A "companion" clk is an accompanying clock to the one being queried
  * that must be enabled for the IP module connected to the clock to
@@ -42,6 +44,8 @@ struct clkops {
 					       u8 *, u8 *);
 	void			(*find_companion)(struct clk *, void __iomem **,
 						  u8 *);
+	void			(*allow_idle)(struct clk *);
+	void			(*deny_idle)(struct clk *);
 };
 
 #ifdef CONFIG_ARCH_OMAP2PLUS
@@ -292,6 +296,8 @@ extern void clk_init_cpufreq_table(struct cpufreq_frequency_table **table);
 extern void clk_exit_cpufreq_table(struct cpufreq_frequency_table **table);
 #endif
 extern struct clk *omap_clk_get_by_name(const char *name);
+extern void omap_clk_enable_autoidle(void);
+extern void omap_clk_disable_autoidle(void);
 
 extern const struct clkops clkops_null;
 
-- 
1.7.2.3