[PATCH] clk: divider: Fix overflow in clk_divider_bestdiv

[PATCH] clk: divider: Fix overflow in clk_divider_bestdiv

[Tomasz Figa]

Commit c686078 ("clk: divider: Add round to closest divider") introduced
a helper function to check whether given divisor is the best one instead
of direct check. However due to int type used instead of unsigned long
for passing calculated rates to this function in certain cases an
overflow could occur, for example when trying to obtain maximum possible
clock rate by calling clk_round_rate(..., UINT_MAX).

This patch fixes this issue by changing the type of rate, now and best
arguments of the function to unsigned long, which is the type that
should be used for clock rates.

Signed-off-by: Tomasz Figa <t.figa@samsung.com>
---
 drivers/clk/clk-divider.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/clk/clk-divider.c b/drivers/clk/clk-divider.c
index c572945..e0b360a 100644
--- a/drivers/clk/clk-divider.c
+++ b/drivers/clk/clk-divider.c
@@ -232,7 +232,7 @@ static int _div_round(struct clk_divider *divider, unsigned long parent_rate,
 }
 
 static bool _is_best_div(struct clk_divider *divider,
-		int rate, int now, int best)
+		unsigned long rate, unsigned long now, unsigned long best)
 {
 	if (divider->flags & CLK_DIVIDER_ROUND_CLOSEST)
 		return abs(rate - now) < abs(rate - best);
-- 
1.9.2

Re: [PATCH] clk: divider: Fix overflow in clk_divider_bestdiv

[Maxime Coquelin]

Hi Tomasz,

On 05/07/2014 06:24 PM, Tomasz Figa wrote:
> Commit c686078 ("clk: divider: Add round to closest divider") introduced
> a helper function to check whether given divisor is the best one instead
> of direct check. However due to int type used instead of unsigned long
> for passing calculated rates to this function in certain cases an
> overflow could occur, for example when trying to obtain maximum possible
> clock rate by calling clk_round_rate(..., UINT_MAX).
>
> This patch fixes this issue by changing the type of rate, now and best
> arguments of the function to unsigned long, which is the type that
> should be used for clock rates.
Good catch.

Acked-by: Maxime Coquelin <maxime.coquelin@st.com>

Thanks,
Maxime
>
> Signed-off-by: Tomasz Figa <t.figa@samsung.com>
> ---
>   drivers/clk/clk-divider.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/clk/clk-divider.c b/drivers/clk/clk-divider.c
> index c572945..e0b360a 100644
> --- a/drivers/clk/clk-divider.c
> +++ b/drivers/clk/clk-divider.c
> @@ -232,7 +232,7 @@ static int _div_round(struct clk_divider *divider, unsigned long parent_rate,
>   }
>
>   static bool _is_best_div(struct clk_divider *divider,
> -		int rate, int now, int best)
> +		unsigned long rate, unsigned long now, unsigned long best)
>   {
>   	if (divider->flags & CLK_DIVIDER_ROUND_CLOSEST)
>   		return abs(rate - now) < abs(rate - best);
>

Re: [PATCH] clk: divider: Fix overflow in clk_divider_bestdiv

[Tomasz Figa]

Hi Mike,

On 07.05.2014 18:24, Tomasz Figa wrote:
> Commit c686078 ("clk: divider: Add round to closest divider") introduced
> a helper function to check whether given divisor is the best one instead
> of direct check. However due to int type used instead of unsigned long
> for passing calculated rates to this function in certain cases an
> overflow could occur, for example when trying to obtain maximum possible
> clock rate by calling clk_round_rate(..., UINT_MAX).
> 
> This patch fixes this issue by changing the type of rate, now and best
> arguments of the function to unsigned long, which is the type that
> should be used for clock rates.
> 
> Signed-off-by: Tomasz Figa <t.figa@samsung.com>
> ---
>  drivers/clk/clk-divider.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/clk/clk-divider.c b/drivers/clk/clk-divider.c
> index c572945..e0b360a 100644
> --- a/drivers/clk/clk-divider.c
> +++ b/drivers/clk/clk-divider.c
> @@ -232,7 +232,7 @@ static int _div_round(struct clk_divider *divider, unsigned long parent_rate,
>  }
>  
>  static bool _is_best_div(struct clk_divider *divider,
> -		int rate, int now, int best)
> +		unsigned long rate, unsigned long now, unsigned long best)
>  {
>  	if (divider->flags & CLK_DIVIDER_ROUND_CLOSEST)
>  		return abs(rate - now) < abs(rate - best);
> 

Ping. It's quite important fix as the issue makes all Exynos boards
using sdhci-s3c almost unusable.

Best regards,
Tomasz

[FIX] [CRITICAL] Re: [PATCH] clk: divider: Fix overflow in clk_divider_bestdiv

[Tomasz Figa]

Mike,

On 15.05.2014 18:51, Tomasz Figa wrote:
> Hi Mike,
> 
> On 07.05.2014 18:24, Tomasz Figa wrote:
>> Commit c686078 ("clk: divider: Add round to closest divider") introduced
>> a helper function to check whether given divisor is the best one instead
>> of direct check. However due to int type used instead of unsigned long
>> for passing calculated rates to this function in certain cases an
>> overflow could occur, for example when trying to obtain maximum possible
>> clock rate by calling clk_round_rate(..., UINT_MAX).
>>
>> This patch fixes this issue by changing the type of rate, now and best
>> arguments of the function to unsigned long, which is the type that
>> should be used for clock rates.
>>
>> Signed-off-by: Tomasz Figa <t.figa@samsung.com>
>> ---
>>  drivers/clk/clk-divider.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/clk/clk-divider.c b/drivers/clk/clk-divider.c
>> index c572945..e0b360a 100644
>> --- a/drivers/clk/clk-divider.c
>> +++ b/drivers/clk/clk-divider.c
>> @@ -232,7 +232,7 @@ static int _div_round(struct clk_divider *divider, unsigned long parent_rate,
>>  }
>>  
>>  static bool _is_best_div(struct clk_divider *divider,
>> -		int rate, int now, int best)
>> +		unsigned long rate, unsigned long now, unsigned long best)
>>  {
>>  	if (divider->flags & CLK_DIVIDER_ROUND_CLOSEST)
>>  		return abs(rate - now) < abs(rate - best);
>>
> 
> Ping. It's quite important fix as the issue makes all Exynos boards
> using sdhci-s3c almost unusable.

Any issues with this patch?

Due to this issue, now since almost 3 weeks, all Samsung boards using
sdhci-s3c have been suffering from boot failures on linux-next due to
incorrect clock rates being calculated.

Best regards,
Tomasz

Re: [PATCH] clk: divider: Fix overflow in clk_divider_bestdiv

[Mike Turquette]

Quoting Tomasz Figa (2014-05-07 09:24:10)
> Commit c686078 ("clk: divider: Add round to closest divider") introduced
> a helper function to check whether given divisor is the best one instead
> of direct check. However due to int type used instead of unsigned long
> for passing calculated rates to this function in certain cases an
> overflow could occur, for example when trying to obtain maximum possible
> clock rate by calling clk_round_rate(..., UINT_MAX).
> 
> This patch fixes this issue by changing the type of rate, now and best
> arguments of the function to unsigned long, which is the type that
> should be used for clock rates.
> 
> Signed-off-by: Tomasz Figa <t.figa@samsung.com>

Sorry for the long wait. This one flew under the radar. Applied to
clk-next.

Regards,
Mike

> ---
>  drivers/clk/clk-divider.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/clk/clk-divider.c b/drivers/clk/clk-divider.c
> index c572945..e0b360a 100644
> --- a/drivers/clk/clk-divider.c
> +++ b/drivers/clk/clk-divider.c
> @@ -232,7 +232,7 @@ static int _div_round(struct clk_divider *divider, unsigned long parent_rate,
>  }
>  
>  static bool _is_best_div(struct clk_divider *divider,
> -               int rate, int now, int best)
> +               unsigned long rate, unsigned long now, unsigned long best)
>  {
>         if (divider->flags & CLK_DIVIDER_ROUND_CLOSEST)
>                 return abs(rate - now) < abs(rate - best);
> -- 
> 1.9.2
>