* [PATCH] clk: fractional-divider: prevent division by zero
@ 2015-01-16 12:37 Heikki Krogerus
2015-01-16 22:29 ` Stephen Boyd
0 siblings, 1 reply; 3+ messages in thread
From: Heikki Krogerus @ 2015-01-16 12:37 UTC (permalink / raw)
To: Mike Turquette, Stephen Boyd
Cc: Mika Westerberg, Andy Shevchenko, linux-kernel
Preventing division by zero condition by making sure that
the initial n and m values are not 0.
Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
---
drivers/clk/clk-fractional-divider.c | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/drivers/clk/clk-fractional-divider.c b/drivers/clk/clk-fractional-divider.c
index 82a59d0..dc91da7 100644
--- a/drivers/clk/clk-fractional-divider.c
+++ b/drivers/clk/clk-fractional-divider.c
@@ -104,6 +104,7 @@ struct clk *clk_register_fractional_divider(struct device *dev,
struct clk_fractional_divider *fd;
struct clk_init_data init;
struct clk *clk;
+ u32 val;
fd = kzalloc(sizeof(*fd), GFP_KERNEL);
if (!fd) {
@@ -126,6 +127,14 @@ struct clk *clk_register_fractional_divider(struct device *dev,
fd->lock = lock;
fd->hw.init = &init;
+ /* Prevent division by zero */
+ val = clk_readl(fd->reg);
+ if (!(val & fd->nmask))
+ val |= 1 << fd->nshift;
+ if (!(val & fd->mmask))
+ val |= 1 << fd->mshift;
+ clk_writel(val, fd->reg);
+
clk = clk_register(dev, &fd->hw);
if (IS_ERR(clk))
kfree(fd);
--
2.1.4
^ permalink raw reply related [flat|nested] 3+ messages in thread* Re: [PATCH] clk: fractional-divider: prevent division by zero
2015-01-16 12:37 [PATCH] clk: fractional-divider: prevent division by zero Heikki Krogerus
@ 2015-01-16 22:29 ` Stephen Boyd
2015-01-19 11:56 ` Heikki Krogerus
0 siblings, 1 reply; 3+ messages in thread
From: Stephen Boyd @ 2015-01-16 22:29 UTC (permalink / raw)
To: Heikki Krogerus, Mike Turquette
Cc: Mika Westerberg, Andy Shevchenko, linux-kernel
On 01/16/2015 04:37 AM, Heikki Krogerus wrote:
> Preventing division by zero condition by making sure that
> the initial n and m values are not 0.
>
> Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
> ---
> drivers/clk/clk-fractional-divider.c | 9 +++++++++
> 1 file changed, 9 insertions(+)
>
> diff --git a/drivers/clk/clk-fractional-divider.c b/drivers/clk/clk-fractional-divider.c
> index 82a59d0..dc91da7 100644
> --- a/drivers/clk/clk-fractional-divider.c
> +++ b/drivers/clk/clk-fractional-divider.c
> @@ -104,6 +104,7 @@ struct clk *clk_register_fractional_divider(struct device *dev,
> struct clk_fractional_divider *fd;
> struct clk_init_data init;
> struct clk *clk;
> + u32 val;
>
> fd = kzalloc(sizeof(*fd), GFP_KERNEL);
> if (!fd) {
> @@ -126,6 +127,14 @@ struct clk *clk_register_fractional_divider(struct device *dev,
> fd->lock = lock;
> fd->hw.init = &init;
>
> + /* Prevent division by zero */
> + val = clk_readl(fd->reg);
> + if (!(val & fd->nmask))
> + val |= 1 << fd->nshift;
> + if (!(val & fd->mmask))
> + val |= 1 << fd->mshift;
> + clk_writel(val, fd->reg);
> +
> clk = clk_register(dev, &fd->hw);
> if (IS_ERR(clk))
> kfree(fd);
Sorry I don't understand this at all. Does your hardware support a value
of 0 in the register? Doesn't that mean "bypass" so that the rate of the
parent bypasses the divider? If so, why aren't we fixing the
recalc_rate() logic to check for a special case of 0?
--
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
a Linux Foundation Collaborative Project
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH] clk: fractional-divider: prevent division by zero
2015-01-16 22:29 ` Stephen Boyd
@ 2015-01-19 11:56 ` Heikki Krogerus
0 siblings, 0 replies; 3+ messages in thread
From: Heikki Krogerus @ 2015-01-19 11:56 UTC (permalink / raw)
To: Stephen Boyd
Cc: Mike Turquette, Mika Westerberg, Andy Shevchenko, linux-kernel
On Fri, Jan 16, 2015 at 02:29:13PM -0800, Stephen Boyd wrote:
> On 01/16/2015 04:37 AM, Heikki Krogerus wrote:
> > Preventing division by zero condition by making sure that
> > the initial n and m values are not 0.
> >
> > Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
> > ---
> > drivers/clk/clk-fractional-divider.c | 9 +++++++++
> > 1 file changed, 9 insertions(+)
> >
> > diff --git a/drivers/clk/clk-fractional-divider.c b/drivers/clk/clk-fractional-divider.c
> > index 82a59d0..dc91da7 100644
> > --- a/drivers/clk/clk-fractional-divider.c
> > +++ b/drivers/clk/clk-fractional-divider.c
> > @@ -104,6 +104,7 @@ struct clk *clk_register_fractional_divider(struct device *dev,
> > struct clk_fractional_divider *fd;
> > struct clk_init_data init;
> > struct clk *clk;
> > + u32 val;
> >
> > fd = kzalloc(sizeof(*fd), GFP_KERNEL);
> > if (!fd) {
> > @@ -126,6 +127,14 @@ struct clk *clk_register_fractional_divider(struct device *dev,
> > fd->lock = lock;
> > fd->hw.init = &init;
> >
> > + /* Prevent division by zero */
> > + val = clk_readl(fd->reg);
> > + if (!(val & fd->nmask))
> > + val |= 1 << fd->nshift;
> > + if (!(val & fd->mmask))
> > + val |= 1 << fd->mshift;
> > + clk_writel(val, fd->reg);
> > +
> > clk = clk_register(dev, &fd->hw);
> > if (IS_ERR(clk))
> > kfree(fd);
>
> Sorry I don't understand this at all. Does your hardware support a value
> of 0 in the register? Doesn't that mean "bypass" so that the rate of the
> parent bypasses the divider? If so, why aren't we fixing the
> recalc_rate() logic to check for a special case of 0?
OK. Makes sense.
--
heikki
^ permalink raw reply [flat|nested] 3+ messages in thread
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2015-01-16 12:37 [PATCH] clk: fractional-divider: prevent division by zero Heikki Krogerus
2015-01-16 22:29 ` Stephen Boyd
2015-01-19 11:56 ` Heikki Krogerus
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