Messages in this thread | | | Date | Wed, 7 May 2014 10:37:42 +0200 | From | Maxime Coquelin <> | Subject | Re: [PATCH] clk: clk-divider: Fix infinite loop for table divider |
| |
Hi Fabio,
On 05/06/2014 10:26 PM, Fabio Estevam wrote: > From: Fabio Estevam <fabio.estevam@freescale.com> > > Since commit e7489693b3 (clk: divider: Optimize clk_divider_bestdiv loop) we > notice a system hang on mx6qboard. > > The cause for the hang is well explained by Sascha Hauer [1]: > > "This cannot work. _round_up_table is implemented like this: > > static int _round_up_table(const struct clk_div_table *table, int div) > { > const struct clk_div_table *clkt; > int up = _get_table_maxdiv(table); > > for (clkt = table; clkt->div; clkt++) { > if (clkt->div == div) > return clkt->div; > ... > } > ... > } > > Here when a table entry matches the input div this function will return > exactly the input div. This means _next_div() will always return the > same value and clk_divider_bestdiv() has an infinite loop: > > for (i = 1; i <= maxdiv; i = _next_div(divider, i)) { > ... > } > " > [1] http://marc.info/?l=linux-arm-kernel&m=139940658726253&w=2 > > Remove the 'return _round_up_table' so that the system can work normally again. > > Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com> > --- > drivers/clk/clk-divider.c | 2 -- > 1 file changed, 2 deletions(-) > > diff --git a/drivers/clk/clk-divider.c b/drivers/clk/clk-divider.c > index b3c8396..fc3e344 100644 > --- a/drivers/clk/clk-divider.c > +++ b/drivers/clk/clk-divider.c > @@ -246,8 +246,6 @@ static int _next_div(struct clk_divider *divider, int div) > > if (divider->flags & CLK_DIVIDER_POWER_OF_TWO) > return __roundup_pow_of_two(div); > - if (divider->table) > - return _round_up_table(divider->table, div);
Couldn't we initialize "up" variable to INT_MAX in _round_up_table() as I just proposed in mail thread reporting the regression?
See http://marc.info/?l=linux-arm-kernel&m=139945172905130&w=2
Regards, Maxime
> > return div; > } >
| |