Re: [PATCH] cpufreq: arm_big_little: fix frequency check when bL switcher is active

[Sudeep Holla]

On 14/10/15 08:12, Jon Medhurst (Tixy) wrote:
> On Tue, 2015-10-13 at 11:36 +0100, Sudeep Holla wrote:
> > On 13/10/15 08:19, Jon Medhurst (Tixy) wrote:
> [...]
> > > But then we wouldn't get the WARN_ON and pr_err triggered when we detect
> > > the clock rate isn't set, which surely is half the reason for the check
> > > in the first place?
> >
> > Not sure if I understand what you mean or may be I was not clear, so
> > thought I will put the delta here. Let me know if and how its still a
> > problem.
> >
> > diff --git i/drivers/cpufreq/arm_big_little.c
> > w/drivers/cpufreq/arm_big_little.c
> > index f1e42f8ce0fc..05e850f80f39 100644
> > --- i/drivers/cpufreq/arm_big_little.c
> > +++ w/drivers/cpufreq/arm_big_little.c
> > @@ -164,6 +164,16 @@ bL_cpufreq_set_rate(u32 cpu, u32 old_cluster, u32
> > new_cluster, u32 rate)
> >
> >           mutex_unlock(&cluster_lock[new_cluster]);
> >
> > +       /*
> > +        * FIXME: clk_set_rate has to handle the case where clk_change_rate
> > +        * can fail due to hardware or firmware issues. Until the clk core
> > +        * layer is fixed, we can check here. In most of the cases we will
> > +        * be reading only the cached value anyway. This needs to  be
> > removed
> > +        * once clk core is fixed.
> > +        */
> > +       if (bL_cpufreq_get_rate(cpu) != new_rate)
> > +               return -EIO;
> > +
> >           /* Recalc freq for old cluster when switching clusters */
> >           if (old_cluster != new_cluster) {
> >                   pr_debug("%s: cpu: %d, old cluster: %d, new cluster: %d\n",
>
> That's what I though you meant, and I can't see why you would want to do
> that and bypass the error reporting for clk_get_rate failing. After all,
> the code we're moving around is explicitly there to workaround the fact
> that clk_set_rate doesn't actually pass through all errors, so it's
> doing additional error checking. (At least, that's what the comment
> says). So this looks more logical to me.

OK, I understand what you mean now. I don't have a strong opinion, but
here is the reason why I prefer the approach I said earlier:
clk_set_rate doesn't return error if the h/w or f/w return error which
is usually the last step. So calling clk_get_rate when clk_set_rate
return error quite early makes no sense to me.

--
Regards,
Sudeep
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