[PATCH] clk: Don't write error code into divider register

[PATCH] clk: Don't write error code into divider register

[Peter De Schrijver]

From: Alex Frid <afrid@nvidia.com>

Add a check for error returned by divider value calculation to avoid
writing error code into hw register.

Signed-off-by: Alex Frid <afrid@nvidia.com>
Reviewed-by: Peter De Schrijver <pdeschrijver@nvidia.com>
Reviewed-by: Jon Mayo <jmayo@nvidia.com>
---
 drivers/clk/clk-divider.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/clk/clk-divider.c b/drivers/clk/clk-divider.c
index 9bb472c..4ed516c 100644
--- a/drivers/clk/clk-divider.c
+++ b/drivers/clk/clk-divider.c
@@ -385,12 +385,14 @@ static int clk_divider_set_rate(struct clk_hw *hw, unsigned long rate,
 				unsigned long parent_rate)
 {
 	struct clk_divider *divider = to_clk_divider(hw);
-	unsigned int value;
+	int value;
 	unsigned long flags = 0;
 	u32 val;
 
 	value = divider_get_val(rate, parent_rate, divider->table,
 				divider->width, divider->flags);
+	if (value < 0)
+		return value;
 
 	if (divider->lock)
 		spin_lock_irqsave(divider->lock, flags);
@@ -403,7 +405,7 @@ static int clk_divider_set_rate(struct clk_hw *hw, unsigned long rate,
 		val = clk_readl(divider->reg);
 		val &= ~(div_mask(divider->width) << divider->shift);
 	}
-	val |= value << divider->shift;
+	val |= (u32)value << divider->shift;
 	clk_writel(val, divider->reg);
 
 	if (divider->lock)
-- 
1.9.1

Re: [PATCH] clk: Don't write error code into divider register

[Stephen Boyd]

On 07/25, Peter De Schrijver wrote:
> From: Alex Frid <afrid@nvidia.com>
> 
> Add a check for error returned by divider value calculation to avoid
> writing error code into hw register.
> 
> Signed-off-by: Alex Frid <afrid@nvidia.com>
> Reviewed-by: Peter De Schrijver <pdeschrijver@nvidia.com>
> Reviewed-by: Jon Mayo <jmayo@nvidia.com>
> ---

Fixes: bca9690b9426 ("clk: divider: Make generic for usage elsewhere")

perhaps?

Also, curious how this got triggered? Presumably round_rate would
have failed before a set_rate call with something invalid came
through so that's why nobody has reported anything so far.

>  drivers/clk/clk-divider.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/clk/clk-divider.c b/drivers/clk/clk-divider.c
> index 9bb472c..4ed516c 100644
> --- a/drivers/clk/clk-divider.c
> +++ b/drivers/clk/clk-divider.c
> @@ -385,12 +385,14 @@ static int clk_divider_set_rate(struct clk_hw *hw, unsigned long rate,
>  				unsigned long parent_rate)
>  {
>  	struct clk_divider *divider = to_clk_divider(hw);
> -	unsigned int value;
> +	int value;
>  	unsigned long flags = 0;
>  	u32 val;
>  
>  	value = divider_get_val(rate, parent_rate, divider->table,
>  				divider->width, divider->flags);
> +	if (value < 0)

Perhaps value should be an s32 if we're doing a writel with it
shifted so much. And then, we could declare it as a u32 and test
it with

	if ((s32)value < 0)

to see if there was an error. Sort of annoying that we've limited
the available space of divider_get_val() by combining the value
with the error code number space. We may want to not do that in
case people have huge dividers.

-- 
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
a Linux Foundation Collaborative Project

Re: [PATCH] clk: Don't write error code into divider register

[Peter De Schrijver]

On Tue, Jul 25, 2017 at 05:32:08PM -0700, Stephen Boyd wrote:
> On 07/25, Peter De Schrijver wrote:
> > From: Alex Frid <afrid@nvidia.com>
> > 
> > Add a check for error returned by divider value calculation to avoid
> > writing error code into hw register.
> > 
> > Signed-off-by: Alex Frid <afrid@nvidia.com>
> > Reviewed-by: Peter De Schrijver <pdeschrijver@nvidia.com>
> > Reviewed-by: Jon Mayo <jmayo@nvidia.com>
> > ---
> 
> Fixes: bca9690b9426 ("clk: divider: Make generic for usage elsewhere")
> 
> perhaps?
> 
> Also, curious how this got triggered? Presumably round_rate would
> have failed before a set_rate call with something invalid came
> through so that's why nobody has reported anything so far.
> 

I don't really know. Aleks do you remember?

> >  drivers/clk/clk-divider.c | 6 ++++--
> >  1 file changed, 4 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/clk/clk-divider.c b/drivers/clk/clk-divider.c
> > index 9bb472c..4ed516c 100644
> > --- a/drivers/clk/clk-divider.c
> > +++ b/drivers/clk/clk-divider.c
> > @@ -385,12 +385,14 @@ static int clk_divider_set_rate(struct clk_hw *hw, unsigned long rate,
> >  				unsigned long parent_rate)
> >  {
> >  	struct clk_divider *divider = to_clk_divider(hw);
> > -	unsigned int value;
> > +	int value;
> >  	unsigned long flags = 0;
> >  	u32 val;
> >  
> >  	value = divider_get_val(rate, parent_rate, divider->table,
> >  				divider->width, divider->flags);
> > +	if (value < 0)
> 
> Perhaps value should be an s32 if we're doing a writel with it
> shifted so much. And then, we could declare it as a u32 and test
> it with
> 
> 	if ((s32)value < 0)
> 
> to see if there was an error. Sort of annoying that we've limited
> the available space of divider_get_val() by combining the value
> with the error code number space. We may want to not do that in
> case people have huge dividers.
> 

Yes. It would have been better to return the divider in a separate variable.
There seem to be few users though, only 6.

Peter.

> -- 
> Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
> a Linux Foundation Collaborative Project

Re: [PATCH] clk: Don't write error code into divider register

[Stephen Boyd]

On 07/26, Peter De Schrijver wrote:
> On Tue, Jul 25, 2017 at 05:32:08PM -0700, Stephen Boyd wrote:
> > On 07/25, Peter De Schrijver wrote:
> > > From: Alex Frid <afrid@nvidia.com>
> > > 
> > > Add a check for error returned by divider value calculation to avoid
> > > writing error code into hw register.
> > > 
> > > Signed-off-by: Alex Frid <afrid@nvidia.com>
> > > Reviewed-by: Peter De Schrijver <pdeschrijver@nvidia.com>
> > > Reviewed-by: Jon Mayo <jmayo@nvidia.com>
> > > ---
> > 
> > Fixes: bca9690b9426 ("clk: divider: Make generic for usage elsewhere")
> > 
> > perhaps?
> > 
> > Also, curious how this got triggered? Presumably round_rate would
> > have failed before a set_rate call with something invalid came
> > through so that's why nobody has reported anything so far.
> > 
> 
> I don't really know. Aleks do you remember?
> 

Still wondering.

> > 	if ((s32)value < 0)
> > 
> > to see if there was an error. Sort of annoying that we've limited
> > the available space of divider_get_val() by combining the value
> > with the error code number space. We may want to not do that in
> > case people have huge dividers.
> > 
> 
> Yes. It would have been better to return the divider in a separate variable.
> There seem to be few users though, only 6.

Patches welcome.

-- 
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
a Linux Foundation Collaborative Project

Re: [PATCH] clk: Don't write error code into divider register

[Stephen Boyd]

On 07/25, Peter De Schrijver wrote:
> From: Alex Frid <afrid@nvidia.com>
> 
> Add a check for error returned by divider value calculation to avoid
> writing error code into hw register.
> 
> Signed-off-by: Alex Frid <afrid@nvidia.com>
> Reviewed-by: Peter De Schrijver <pdeschrijver@nvidia.com>
> Reviewed-by: Jon Mayo <jmayo@nvidia.com>
> ---

Applied to clk-next

-- 
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
a Linux Foundation Collaborative Project