Re: [PATCH v3 1/5] powernv: cpufreq driver for powernv platform

[Gautham R Shenoy <ego@linux.vnet.ibm.com>]

Hi Viresh,

On Fri, Mar 21, 2014 at 04:24:27PM +0530, Viresh Kumar wrote:
> On 21 March 2014 16:13, Gautham R Shenoy <ego@linux.vnet.ibm.com> wrote:
> > On Fri, Mar 21, 2014 at 02:11:32PM +0530, Viresh Kumar wrote:
> 
> >> > +               pr_debug("PState id %d freq %d MHz\n", id, freq);
> >> > +               powernv_freqs[i].driver_data = i;
> >>
> >> I don't think you are using this field at all and this is the field you can
> >> use for driver_data and so you can get rid of powernv_pstate_ids[ ].
> >
> > Using driver_data to record powernv_pstate_ids won't work since
> > powernv_pstate_ids can be negative. So a pstate_id -3 can be confused
> > with CPUFREQ_BOOST_FREQ thereby not displaying the frequency
> > corresponding to pstate id -3. So for now I think we will be retaining
> > powernv_pstate_ids.
> 
> As I said earlier, this field is only used by cpufreq drivers and cpufreq core
> isn't supposed to touch it. CPUFREQ_BOOST_FREQ and other macros
> are there for .frequency field and not this one.
> 

Ok, I had based my code on linus's git tree. I checked the 'pm-cpufreq'
branch of Rafael's 'linux-pm' tree and freq_table.c contains the
following code snippet in show_available_frequencies:

	if (show_boost ^ (table[i].driver_data == CPUFREQ_BOOST_FREQ))
			continue;

I suspect we're talking about different code bases. So could you
please tell me which one should I be looking at ?

> 
> >> > +static int powernv_cpufreq_cpu_init(struct cpufreq_policy *policy)
> >> > +{
> >> > +       int base, i;
> >> > +
> >> > +#ifdef CONFIG_SMP
> >>
> >> What will break if you don't have this ifdef here? Without that as well
> >> below code should work?
> 
> Missed this one?
> 
> >> > +       base = cpu_first_thread_sibling(policy->cpu);
> >> > +
> >> > +       for (i = 0; i < threads_per_core; i++)
> >> > +               cpumask_set_cpu(base + i, policy->cpus);
> >> > +#endif
> >> > +       policy->cpuinfo.transition_latency = 25000;
> >> > +
> >> > +       policy->cur = powernv_freqs[0].frequency;
> >> > +       cpufreq_frequency_table_get_attr(powernv_freqs, policy->cpu);
> >>
> >> This doesn't exist anymore.
> >
> > Didn't get this comment!
> 
> cpufreq_frequency_table_get_attr() routine doesn't exist anymore.
> 
> >> > +static int powernv_cpufreq_cpu_exit(struct cpufreq_policy *policy)
> >> > +{
> >> > +       cpufreq_frequency_table_put_attr(policy->cpu);
> >> > +       return 0;
> >> > +}
> >>
> >> You don't need this..
> >
> > Why not ?
> 
> Because cpufreq_frequency_table_get_attr() and
> cpufreq_frequency_table_put_attr() don't exist anymore :)

Well, it does in the codebases that I was looking at. May be I've been
looking at the wrong place.

> 
> >> > +module_init(powernv_cpufreq_init);
> >> > +module_exit(powernv_cpufreq_exit);
> >>
> >> Place these right after the routines without any blank lines in
> > between.
> >
> > Is this the new convention ?
> 
> Don't know I have been following this since long time, probably from the
> time I started with Mainline stuff.. I have seen many maintainers advising this
> as it make code more readable, specially if these routines are quite big..
> 
> Probably it isn't mentioned in coding guidelines but people follow it most of
> the times.

Ok. I was not aware of this. Good to know :-)
> 

--
Thanks and Regards
gautham.