Re: [PATCH] ARM: SAMSUNG: s3c_set_clksrc returns for single parent clock.

[Ben Dooks <ben-linux@fluff.org>]

On Mon, Jan 18, 2010 at 10:34:29AM +0900, Thomas Abraham wrote:
> Hi Ben,
> 
> On Mon, Jan 18, 2010 at 10:10 AM, Ben Dooks <ben-linux@fluff.org> wrote:
> > On Mon, Jan 18, 2010 at 09:38:17AM +0900, Thomas Abraham wrote:
> >> The function s3c_set_clksrc should return if the clksrc_clk clock has
> >> only one possible parent clock.
> >
> > Does this actually relate to a real bug or is this something that you've
> > come across whilst reading the code?
> 
> This is required in cases where a clock has a divider but no mux. In
> s3c_register_clksrc function, after the default set of clock
> operations are assigned, the parent clock set function s3c_set_clksrc
> is called. For clocks that do not have mux, the call to s3c_set_clksrc
> is incorrect.

If you have a look at s3c_set_clksrc() , you will find it already
checks to see if clk->reg_src.reg is set. It also doesn't call the
setparent directly either, as it only needs to set clk->clk.parent
field before exiting.

   132          u32 clksrc = 0;
   133  
   134          if (clk->reg_src.reg)
   135                  clksrc = __raw_readl(clk->reg_src.reg);
   136  
   137          clksrc &= mask;
   138          clksrc >>= clk->reg_src.shift;
   139  
   140          if (clksrc > srcs->nr_sources || !srcs->sources[clksrc]) {
   141                  printk(KERN_ERR "%s: bad source %d\n",
   142                         clk->clk.name, clksrc);
   143                  return;
   144          }
   145  
   146          clk->clk.parent = srcs->sources[clksrc];

This allows us to do some basic verification that the clksrc's sources
data is valud (such that srcs->nr_sources at least contains one source
and that it is not NULL).
 
> >
> > From arch/arm/plat-samnsung/clock-clksrc.c:
> >
> >   181                          if (!clksrc->reg_div.reg)
> >   182                                  clksrc->clk.ops = &clksrc_ops_nodiv;
> >   183                          else if (!clksrc->reg_src.reg)
> >   184                                  clksrc->clk.ops = &clksrc_ops_nosrc;
> >   185                          else
> >   186                                  clksrc->clk.ops = &clksrc_ops;
> >
> > So we change the ops dependant on which register(s) we have availalbe.
> >
> >> Signed-of-by:  Thomas Abraham <thomas.ab@samsung.com>
> >> ---
> >>  arch/arm/plat-samsung/clock-clksrc.c |    5 +++--
> >>  1 files changed, 3 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/arch/arm/plat-samsung/clock-clksrc.c b/arch/arm/plat-samsung/clock-clksrc.c
> >> index 33c633a..80da4c4 100644
> >> --- a/arch/arm/plat-samsung/clock-clksrc.c
> >> +++ b/arch/arm/plat-samsung/clock-clksrc.c
> >> @@ -131,9 +131,10 @@ void __init_or_cpufreq s3c_set_clksrc(struct clksrc_clk *clk, bool announce)
> >>       u32 mask = bit_mask(clk->reg_src.shift, clk->reg_src.size);
> >>       u32 clksrc = 0;
> >>
> >> -     if (clk->reg_src.reg)
> >> -             clksrc = __raw_readl(clk->reg_src.reg);
> >> +     if (!clk->reg_src.reg)
> >> +             return;
> >>
> >> +     clksrc = __raw_readl(clk->reg_src.reg);
> >>       clksrc &= mask;
> >>       clksrc >>= clk->reg_src.shift;
> >>
> >> --
> >> 1.6.3.3
> >>
> >
> > --
> > --
> > Ben
> >
> > Q:      What's a light-year?
> > A:      One-third less calories than a regular year.
> >
> > --
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> >
> 
> 
> Thanks,
> Thomas.
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-- 
-- 
Ben

Q:      What's a light-year?
A:      One-third less calories than a regular year.