Re: cpufreq implementation for OMAP under xen hypervisor.

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

On Tue, Sep 30, 2014 at 01:28:42PM +0300, Oleksandr Dmytryshyn wrote:
> On Mon, Sep 29, 2014 at 6:18 PM, Konrad Rzeszutek Wilk
> <konrad.wilk@oracle.com> wrote:
> >
> > On Mon, Sep 29, 2014 at 12:45:36PM +0300, Oleksandr Dmytryshyn wrote:
> > > On Fri, Sep 26, 2014 at 9:13 PM, Konrad Rzeszutek Wilk
> > > <konrad.wilk@oracle.com> wrote:
> > > >
> > > > > > The architecture looks sane to me. As Konrad pointed out, the difficulty
> > > > > > here is to be able to upstream the changes to the Linux driver in 2),
> > > > > > that you later in the thread identified as
> > > > > > drivers/cpufreq/cpufreq-cpu0.c.
> > > > > I'll write driver drivers/xen/xen-cpufreq.c and it replace original
> > > > > drivers/cpufreq/cpufreq.c
> > > > > And in the original cpufreq-cpu0 driver I'll chande only one string -
> > > > > path in the device tree
> > > > > with the settings for the CPUs opp:
> > > > > string
> > > > > np = of_find_node_by_path("/cpus/cpu@0");
> > > > > will changed to:
> > > > > np = of_find_node_by_path("/cpus/cpu@0/private_data/cpu@0");
> > > > >
> > > > > > If the changes are not invasive and you manage to upstream them in
> > > > > > Linux, I am all for this solution.
> > > > > In Linux kernel I should make few changes:
> > > > > 1. Enable CONFIG_CPU_FREQ_TABLE
> > > > > with disabled CONFIG_CPU_FREQ
> > > > > 2. Enable CONFIG_GENERIC_CPUFREQ_CPU0
> > > > > with disabled CONFIG_CPU_FREQ
> > > > >
> > > > > I mean make those configs dependent on
> > > > > CONFIG_CPU_FREQ or CONFIX_XEN_DOM0
> > > > > instead of
> > > > > CONFIG_CPU_FREQ
> > > >
> > > > Gosh no. Please make it work runtime.
> > > Sorry, Konrad, could You please explain what did You mean.
> >
> > Don't make XEN options disable other options.
> >
> > Distributions want one kernel that can satisfi a variety of platforms - not just specifc ones.
> XEN option will not disable other options. On the contrary, it will
> extend them. In my case XEN option
> will allow to select more options.
> 
> Please, see example
> diff --git a/drivers/cpufreq/Kconfig b/drivers/cpufreq/Kconfig
> index cbcb21e..4531e04 100644
> --- a/drivers/cpufreq/Kconfig
> +++ b/drivers/cpufreq/Kconfig
> @@ -15,11 +15,15 @@ config CPU_FREQ
> 
>           If in doubt, say N.
> 
> -if CPU_FREQ
> +if CPU_FREQ || XEN_DOM0
> 
>  config CPU_FREQ_TABLE
>         tristate
> 
> @@ -184,6 +188,10 @@ config CPU_FREQ_GOV_CONSERVATIVE
> 
>           If in doubt, say N.
> 
> +if CPU_FREQ || XEN_DOM0
> +

Ah, then it is fine. Sorry for the misunderstanding.
>  config GENERIC_CPUFREQ_CPU0
>         tristate "Generic CPU0 cpufreq driver"
>         depends on HAVE_CLK && REGULATOR && PM_OPP && OF