Re: cpufreq implementation for OMAP under xen hypervisor.

[Oleksandr Dmytryshyn <oleksandr.dmytryshyn@globallogic.com>]

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
+
 config GENERIC_CPUFREQ_CPU0
        tristate "Generic CPU0 cpufreq driver"
        depends on HAVE_CLK && REGULATOR && PM_OPP && OF