Messages in this thread | | | Date | Thu, 22 Apr 2010 17:00:00 -0600 | From | Tim Gardner <> | Subject | Re: [PATCH 1/1] arm: mxc: utilise usecount field in clock operations |
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On 04/22/2010 02:30 PM, Amit Kucheria wrote: > From: Amit Kucheria<amit.kucheria@canonical.com> > > This patch fixes the clock refcounting when reparenting is used. > > Sascha just pointed out a good explanation of refcounting here: > http://www.spinics.net/lists/arm-kernel/msg85879.html > > Signed-off-by: Amit Kucheria<amit.kucheria@canonical.com> > --- > arch/arm/plat-mxc/clock.c | 34 ++++++++++++++++++++++------------ > 1 files changed, 22 insertions(+), 12 deletions(-) > > diff --git a/arch/arm/plat-mxc/clock.c b/arch/arm/plat-mxc/clock.c > index 323ff8c..14781cc 100644 > --- a/arch/arm/plat-mxc/clock.c > +++ b/arch/arm/plat-mxc/clock.c > @@ -50,15 +50,16 @@ static DEFINE_MUTEX(clocks_mutex); > > static void __clk_disable(struct clk *clk) > { > - if (clk == NULL || IS_ERR(clk)) > + WARN_ON(!clk->usecount); > + if (clk == NULL || IS_ERR(clk) || !clk->usecount) > return; >
The clk==NULL check seem superfluous if WARN_ON(!clk->usecount) has already dereferenced clk (and possibly crashed). You might need two statements if its likely that clk could be NULL.
> - __clk_disable(clk->parent); > - __clk_disable(clk->secondary); > - > - WARN_ON(!clk->usecount); > - if (!(--clk->usecount)&& clk->disable) > - clk->disable(clk); > + if (!(--clk->usecount)) { > + if (clk->disable) > + clk->disable(clk); > + __clk_disable(clk->parent); > + __clk_disable(clk->secondary); > + } > } > > static int __clk_enable(struct clk *clk) > @@ -66,12 +67,13 @@ static int __clk_enable(struct clk *clk) > if (clk == NULL || IS_ERR(clk)) > return -EINVAL; > > - __clk_enable(clk->parent); > - __clk_enable(clk->secondary); > - > - if (clk->usecount++ == 0&& clk->enable) > - clk->enable(clk); > + if (clk->usecount++ == 0) { > + __clk_enable(clk->parent); > + __clk_enable(clk->secondary); > > + if (clk->enable) > + clk->enable(clk); > + } > return 0; > } > > @@ -160,17 +162,25 @@ EXPORT_SYMBOL(clk_set_rate); > int clk_set_parent(struct clk *clk, struct clk *parent) > { > int ret = -EINVAL; > + struct clk *prev_parent = clk->parent; > > if (clk == NULL || IS_ERR(clk) || parent == NULL || > IS_ERR(parent) || clk->set_parent == NULL) > return ret; > > + if (clk->usecount != 0) > + clk_enable(parent); > + > mutex_lock(&clocks_mutex); > ret = clk->set_parent(clk, parent); > if (ret == 0) > clk->parent = parent; > + > mutex_unlock(&clocks_mutex); > > + if (clk->usecount != 0) > + clk_disable(prev_parent); > + > return ret; > } > EXPORT_SYMBOL(clk_set_parent);
-- Tim Gardner tim.gardner@canonical.com
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