Re: [PATCH V3 2/2] cpufreq: OMAP: instantiate omap-cpufreq as a platform_driver

[Nishanth Menon <nm@ti.com>]

On 08:29-20130329, Viresh Kumar wrote:
> On Fri, Mar 29, 2013 at 3:22 AM, Nishanth Menon <nm@ti.com> wrote:
> > As multi-platform build is being adopted by more and more ARM platforms,
> > initcall function should be used very carefully.  For example, when
> > CONFIG_ARM_OMAP2PLUS_CPUFREQ is built in the kernel, omap_cpufreq_init()
> > will be called on all the platforms to initialize omap-cpufreq driver.
> >
> > Further, on OMAP, we now use Soc generic cpufreq-cpu0 driver using device
> > tree entries.  To allow cpufreq-cpu0 and omap-cpufreq drivers to co-exist
> > for OMAP in a single image, we need to ensure the following:
> > 1. With device tree boot, we use cpufreq-cpu0
> > 2. With non device tree boot, we use omap-cpufreq
> >
> > In the case of (1), we will have cpu OPPs and regulator registered
> > as part of the device tree nodes, to ensure that omap-cpufreq
> > and cpufreq-cpu0 don't conflict in managing the frequency of the
> > same CPU, we should not permit omap-cpufreq to be probed.
> >
> > In the case of (2), we will not have the cpufreq-cpu0 device, hence
> > only omap-cpufreq will be active.
> >
> > To eliminate this undesired these effects, we change omap-cpufreq
> > driver to have it instantiated as a platform_driver and register
> > "omap-cpufreq" device only when booted without device tree nodes on
> > OMAP platforms.
> >
> > This allows the following:
> > a) Will only run on platforms that create the platform_device
> >    "omap-cpufreq".
> > b) Since the platform_device is registered only when device tree nodes
> >    are *not* populated, omap-cpufreq driver does not conflict with
> >    the usage of cpufreq-cpu0 driver which is used on OMAP platforms when
> >    device tree nodes are present.
> >
> > Inspired by commit 5553f9e26f6f49a93ba732fd222eac6973a4cf35
> > (cpufreq: instantiate cpufreq-cpu0 as a platform_driver)
> >
> > Cc: Kevin Hilman <khilman@linaro.org>
> > Cc: Rajendra Nayak <rnayak@ti.com>
> > Cc: Paul Walmsley <paul@pwsan.com>
> > Cc: "Benoît Cousson" <b-cousson@ti.com>
> > Cc: Jon Hunter <jon-hunter@ti.com>
> > Cc: Keerthy <j-keerthy@ti.com>
> > Cc: Santosh Shilimkar <santosh.shilimkar@ti.com>
> > Cc: Shawn Guo <shawn.guo@linaro.org>
> > [robherring2@gmail.com: reported conflict of omap-cpufreq vs other
> > driver in an non-device tree supported boot]
> > Reported-by: Rob Herring <robherring2@gmail.com>
> > Signed-off-by: Nishanth Menon <nm@ti.com>
> > ---
> > Changes in V3:
> >         - converted to platform_driver to
> >                 address https://patchwork.kernel.org/patch/2303491/ as well
> >         - modified CC list.
> > V2: https://patchwork.kernel.org/patch/2303491/
> > V1: https://patchwork.kernel.org/patch/2273681/
> >
> >  arch/arm/mach-omap2/pm.c       |    9 +++++++++
> >  drivers/cpufreq/omap-cpufreq.c |   19 ++++++++++++++-----
> >  2 files changed, 23 insertions(+), 5 deletions(-)
> 
> For cpufreq core:
> 
> Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Since this patch could be merged independently to help multi-platform
builds, While the omap community discusses:
http://marc.info/?t=136450773400004&r=1&w=2
http://marc.info/?t=136370325600009&r=1&w=2&n=7

To enable cpufreq-cpu0 driver in DT mode, I wonder if we could queue this up
for 3.10.
-- 
Regards,
Nishanth Menon