[trusty] [PATCH 2/3] cpufreq: powernv: Use cpufreq_frequency_table.driver_data to store pstate ids

[Seth Forshee]

On Mon, Apr 21, 2014 at 11:29:47AM +0530, Gautham R Shenoy wrote:
> On Fri, Apr 18, 2014 at 08:12:01AM -0500, Seth Forshee wrote:
> > On Thu, Apr 17, 2014 at 12:37:00PM -0300, Mauricio Faria de Oliveira wrote:
> > > From: "Gautham R. Shenoy" <ego at linux.vnet.ibm.com>
> > > 
> > > The .driver_data field in the cpufreq_frequency_table was supposed to
> > > be private to the drivers. However at some later point, it was being
> > > used to indicate if the particular frequency in the table is the
> > > BOOST_FREQUENCY. After patches [1] and [2], the .driver_data is once
> > > again private to the driver. Thus we can safely use
> > > cpufreq_frequency_table.driver_data to store pstate_ids instead of
> > > having to maintain a separate array powernv_pstate_ids[] for this
> > > purpose.
> > > 
> > > [1]:
> > >   Subject: cpufreq: don't print value of .driver_data from core
> > >   From   : Viresh Kumar <viresh.kumar@ linaro.org>
> > >   url    : http://marc.info/?l=linux-pm&m=139601421504709&w=2
> > > 
> > > [2]:
> > >   Subject: cpufreq: create another field .flags in cpufreq_frequency_table
> > >   From   : Viresh Kumar <viresh.kumar at linaro.org>
> > >   url    : http://marc.info/?l=linux-pm&m=139601416804702&w=2
> > 
> > These two commits were merged by Linus in 3.15-rc1, and we don't have
> > them in trusty. Aren't we going to need these too?
> 
> We need these two patches as well since the my patch which makes use
> of .driver_data field to record the pstates is safe only when these
> two patches are applied.

I looked again. [1] could be backported, but it doesn't really seem
necessary as it only affects a printk (i.e. read) of driver_data and
thus shouldn't interfere with the use in your patch. [2] doesn't make
sense for trusty though, because the boost support didn't appear until
3.14 (and thus there's no use of driver_data for storing
CPUFREQ_BOOST_FREQ in trusty).

I don't see anything else in the core cpufreq code in trusty which
touches driver data in struct cpufreq_frequency_table, so I think we
should be okay. Let me know if you find something I missed.

Thanks,
Seth