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

[Viresh Kumar <viresh.kumar@linaro.org>]

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>