[PATCH] ARM: mach-shmobile: sh7372 divide-by-zero FSIDIV fix

[PATCH] ARM: mach-shmobile: sh7372 divide-by-zero FSIDIV fix

[Magnus Damm]

From: Magnus Damm <damm@opensource.se>

Update the sh7372 FSIDIV clock code to bail out
with -EINVAL in case of rate is zero.

Without this fix divide-by-zero is triggering
on sh7372 platforms during system wide resume
of Suspend-to-RAM.

Signed-off-by: Magnus Damm <damm@opensource.se>
---

 arch/arm/mach-shmobile/clock-sh7372.c |    3 +++
 1 file changed, 3 insertions(+)

--- 0001/arch/arm/mach-shmobile/clock-sh7372.c
+++ work/arch/arm/mach-shmobile/clock-sh7372.c	2011-06-09 15:45:41.000000000 +0900
@@ -460,6 +460,9 @@ static int fsidiv_set_rate(struct clk *c
 {
 	int idx;
 
+	if (!rate)
+		return -EINVAL;
+
 	idx = (clk->parent->rate / rate) & 0xffff;
 	if (idx < 2)
 		return -EINVAL;

Re: [PATCH] ARM: mach-shmobile: sh7372 divide-by-zero FSIDIV fix

[Simon Horman]

On Thu, Jun 09, 2011 at 03:49:13PM +0900, Magnus Damm wrote:
> From: Magnus Damm <damm@opensource.se>
> 
> Update the sh7372 FSIDIV clock code to bail out
> with -EINVAL in case of rate is zero.
> 
> Without this fix divide-by-zero is triggering
> on sh7372 platforms during system wide resume
> of Suspend-to-RAM.

Hi Magnus,

I'm unsure that I understand how rate ends up being
zero in the situation you describe.

> 
> Signed-off-by: Magnus Damm <damm@opensource.se>
> ---
> 
>  arch/arm/mach-shmobile/clock-sh7372.c |    3 +++
>  1 file changed, 3 insertions(+)
> 
> --- 0001/arch/arm/mach-shmobile/clock-sh7372.c
> +++ work/arch/arm/mach-shmobile/clock-sh7372.c	2011-06-09 15:45:41.000000000 +0900
> @@ -460,6 +460,9 @@ static int fsidiv_set_rate(struct clk *c
>  {
>  	int idx;
>  
> +	if (!rate)
> +		return -EINVAL;
> +
>  	idx = (clk->parent->rate / rate) & 0xffff;
>  	if (idx < 2)
>  		return -EINVAL;
> --
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Re: [PATCH] ARM: mach-shmobile: sh7372 divide-by-zero FSIDIV fix

[Magnus Damm]

On Fri, Jun 10, 2011 at 11:23 AM, Simon Horman <horms@verge.net.au> wrote:
> On Thu, Jun 09, 2011 at 03:49:13PM +0900, Magnus Damm wrote:
>> From: Magnus Damm <damm@opensource.se>
>>
>> Update the sh7372 FSIDIV clock code to bail out
>> with -EINVAL in case of rate is zero.
>>
>> Without this fix divide-by-zero is triggering
>> on sh7372 platforms during system wide resume
>> of Suspend-to-RAM.
>
> Hi Magnus,
>
> I'm unsure that I understand how rate ends up being
> zero in the situation you describe.

Hi Simon,

During Suspend-to-RAM resume the function clks_core_resume() in
drivers/sh/clk/core.c gets executed. This function goes through all
clocks and sets their rate. In some cases the rate happens to be zero,
and for the FSIDIV the zero turns into a divide-by-zero.

This can easily be triggered by using Suspend-to-RAM on for instance a
Mackerel board.

/ magnus

Re: [PATCH] ARM: mach-shmobile: sh7372 divide-by-zero FSIDIV fix

[Simon Horman]

On Fri, Jun 10, 2011 at 01:54:47PM +0900, Magnus Damm wrote:
> On Fri, Jun 10, 2011 at 11:23 AM, Simon Horman <horms@verge.net.au> wrote:
> > On Thu, Jun 09, 2011 at 03:49:13PM +0900, Magnus Damm wrote:
> >> From: Magnus Damm <damm@opensource.se>
> >>
> >> Update the sh7372 FSIDIV clock code to bail out
> >> with -EINVAL in case of rate is zero.
> >>
> >> Without this fix divide-by-zero is triggering
> >> on sh7372 platforms during system wide resume
> >> of Suspend-to-RAM.
> >
> > Hi Magnus,
> >
> > I'm unsure that I understand how rate ends up being
> > zero in the situation you describe.
> 
> Hi Simon,
> 
> During Suspend-to-RAM resume the function clks_core_resume() in
> drivers/sh/clk/core.c gets executed. This function goes through all
> clocks and sets their rate. In some cases the rate happens to be zero,
> and for the FSIDIV the zero turns into a divide-by-zero.

Ok, understood.