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Message-Id: <1332404298-18891-1-git-send-email-LW@KARO-electronics.de>
Date: Thu, 22 Mar 2012 09:18:17 +0100
From: Lothar Waßmann <LW@...O-electronics.de>
To: Shawn Guo <shawn.guo@...aro.org>
Cc: Lothar Waßmann <LW@...O-electronics.de>,
Sascha Hauer <kernel@...gutronix.de>,
Russell King <linux@....linux.org.uk>,
linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH] ARM: mxs: enforce semantics of clk_prepare()/clk_unprepare() and clk_enable()/clk_disable()
After introducing clk_prepare()/clk_unprepare() there may still be
drivers out there that don't use the new functions.
This patch warns about drivers calling clk_enable() without a
preceding clk_prepare() and various other invalid sequences of calls
to clk_enable()/clk_disable() and clk_prepare()/clk_unprepare().
To not make a system unusable due to excessive warning messages the
warnings are limited to 1 per clk by a flag in the 'flags' member of
struct clk.
Signed-off-by: Lothar Waßmann <LW@...O-electronics.de>
---
arch/arm/mach-mxs/clock.c | 98 ++++++++++++++++++++++++++++----
arch/arm/mach-mxs/include/mach/clock.h | 6 ++
2 files changed, 93 insertions(+), 11 deletions(-)
diff --git a/arch/arm/mach-mxs/clock.c b/arch/arm/mach-mxs/clock.c
index 97a6f4a..4c23351 100644
--- a/arch/arm/mach-mxs/clock.c
+++ b/arch/arm/mach-mxs/clock.c
@@ -56,24 +56,61 @@ static void __clk_disable(struct clk *clk)
if (!(--clk->usecount)) {
if (clk->disable)
clk->disable(clk);
- __clk_disable(clk->parent);
}
}
static int __clk_enable(struct clk *clk)
{
- if (clk == NULL || IS_ERR(clk))
- return -EINVAL;
+ if (clk == NULL)
+ return 0;
- if (clk->usecount++ == 0) {
- __clk_enable(clk->parent);
+ if (IS_ERR(clk))
+ return -EINVAL;
- if (clk->enable)
- clk->enable(clk);
+ if (clk->usecount == 0) {
+ if (clk->enable) {
+ int ret = clk->enable(clk);
+ if (ret)
+ return ret;
+ }
}
+ clk->usecount++;
+
return 0;
}
+static void __clk_unprepare(struct clk *clk)
+{
+ if (clk == NULL || IS_ERR(clk))
+ return;
+
+ if (clk->parent)
+ __clk_unprepare(clk->parent);
+
+ __clk_disable(clk);
+}
+
+static int __clk_prepare(struct clk *clk)
+{
+ int ret;
+
+ if (clk == NULL)
+ return 0;
+
+ if (IS_ERR(clk))
+ return -EINVAL;
+
+ ret = __clk_prepare(clk->parent);
+ if (ret)
+ return ret;
+
+ ret = __clk_enable(clk);
+ if (ret)
+ __clk_unprepare(clk->parent);
+
+ return ret;
+}
+
/*
* The clk_enable/clk_disable could be called by drivers in atomic context,
* so they should not really hold mutex. Instead, clk_prepare/clk_unprepare
@@ -86,11 +123,18 @@ int clk_prepare(struct clk *clk)
{
int ret = 0;
- if (clk == NULL || IS_ERR(clk))
+ if (clk == NULL)
+ return 0;
+
+ if (IS_ERR(clk))
return -EINVAL;
mutex_lock(&clocks_mutex);
- ret = __clk_enable(clk);
+ if (clk->prepared++ == 0) {
+ ret = __clk_prepare(clk);
+ if (ret)
+ clk->prepared--;
+ }
mutex_unlock(&clocks_mutex);
return ret;
@@ -103,20 +147,52 @@ void clk_unprepare(struct clk *clk)
return;
mutex_lock(&clocks_mutex);
- __clk_disable(clk);
+ if (WARN_ON(!clk->prepared && !(clk->flags & CLK_WARNED))) {
+ pr_err("clk_unprepare() called without clk_prepare()\n");
+ clk->flags |= CLK_WARNED;
+ }
+ if (WARN_ON(clk->prepared == 1 && clk->usecount > 1)) {
+ pr_err("unbalanced calls (%d) to clk_enable()/clk_disable() before clk_unprepare()\n",
+ clk->usecount);
+ clk->flags |= CLK_WARNED;
+ }
+ if (!(--clk->prepared))
+ __clk_unprepare(clk);
mutex_unlock(&clocks_mutex);
}
EXPORT_SYMBOL(clk_unprepare);
int clk_enable(struct clk *clk)
{
+ if (clk == NULL)
+ return 0;
+
+ if (IS_ERR(clk))
+ return -EINVAL;
+
+ if (WARN_ON(!clk->prepared && !(clk->flags & CLK_WARNED))) {
+ pr_err("clk_enable() called without clk_prepare()\n");
+ clk->flags |= CLK_WARNED;
+ }
+ clk->usecount++;
return 0;
}
EXPORT_SYMBOL(clk_enable);
void clk_disable(struct clk *clk)
{
- /* nothing to do */
+ if (clk == NULL || IS_ERR(clk))
+ return;
+
+ if (WARN_ON(!clk->prepared && !(clk->flags & CLK_WARNED))) {
+ pr_err("clk_disable() called without clk_prepare()\n");
+ clk->flags |= CLK_WARNED;
+ }
+ if (WARN_ON(clk->usecount <= 1 && !(clk->flags & CLK_WARNED))) {
+ pr_err("unbalanced clk_disable()\n");
+ clk->flags |= CLK_WARNED;
+ }
+ clk->usecount--;
}
EXPORT_SYMBOL(clk_disable);
diff --git a/arch/arm/mach-mxs/include/mach/clock.h b/arch/arm/mach-mxs/include/mach/clock.h
index 592c9ab..285ca6b 100644
--- a/arch/arm/mach-mxs/include/mach/clock.h
+++ b/arch/arm/mach-mxs/include/mach/clock.h
@@ -25,12 +25,18 @@
struct module;
+enum clk_flags {
+ CLK_WARNED = 0x01,
+};
+
struct clk {
int id;
/* Source clock this clk depends on */
struct clk *parent;
/* Reference count of clock enable/disable */
__s8 usecount;
+ /* Reference count of clock prepare/unprepare */
+ __s8 prepared;
/* Register bit position for clock's enable/disable control. */
u8 enable_shift;
/* Register address for clock's enable/disable control. */
--
1.7.2.5
--
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