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SubjectRe: [PATCH 11/13] arm64: dts: qcom: qcs404: Add CPR and populate OPP table
On Tue, Jul 16, 2019 at 04:04:36PM +0530, Viresh Kumar wrote:
> On 15-07-19, 15:24, Niklas Cassel wrote:
> > This was actually my initial thought when talking to you 6+ months ago.
> > However, the problem was that, from the CPR drivers' perspective, it
> > only sees the CPR OPP table.
> >
> >
> > So this is the order things are called,
> > from qcom-cpufreq-nvmem.c perspective:
> >
> > 1) dev_pm_opp_set_supported_hw()
> >
> > 2) dev_pm_opp_attach_genpd() ->
> > which results in
> > int cpr_pd_attach_dev(struct generic_pm_domain *domain,
> > struct device *dev)
> > being called.
> > This callback is inside the CPR driver, and here we have the
> > CPU's (genpd virtual) struct device, and this is where we would like to
> > know the opp-hz.
> > The problem here is that:
> > [ 3.114979] cpr_pd_attach_dev: dev_pm_opp_get_opp_count for dev: genpd:0:cpu0: -19
> > [ 3.119610] cpr_pd_attach_dev: dev_pm_opp_get_opp_count for dev: cpu0: 0

Here I cheated and simply used get_cpu_device(0).

Since I cheated, I used get_cpu_device(0) always,
so even when CPU1,CPU2,CPU3 is attached, dev_pm_opp_get_opp_count(cpu0) is
still 0.

I added a print in
[ 3.836533] cpr_set_performance: number of OPPs for dev: cpu0: 3

And there I can see that OPP count is 3, so it appears that with the
current code, we need to wait until cpufreq-dt.c:cpufreq_init()
has been called, maybe dev_pm_opp_of_cpumask_add_table() needs
to be called before dev_pm_opp_get_opp_count(cpu0) actually returns 3.

cpufreq_init() is called by platform_device_register_simple("cpufreq-dt", -1,
NULL, 0);
which is called after dev_pm_opp_attach_genpd().

What I don't understand is that dev_pm_opp_attach_genpd() actually returns
a OPP table. So why do we need to wait for dev_pm_opp_of_cpumask_add_table(),
before either dev_pm_opp_get_opp_count(cpu0) or
dev_pm_opp_get_opp_count(genpd_virtdev_for_cpu0) returns 3?



> > [ 3.126489] cpr_pd_attach_dev: dev_pm_opp_get_opp_count for dev: cpr@b018000: 3
> >
> > While we have the CPR OPP table in the attach callback, we don't
> > have the CPU OPP table, neither in the CPU struct device or the genpd virtual
> > struct device.
>
> If you can find CPU's physical number from the virtual device, then
> you can do get_cpu_device(X) and then life will be easy ?
>
> > Since we have called dev_pm_opp_attach_genpd(.., .., &virt_devs) which
> > attaches an OPP table to the CPU, I would have expected one of them to
> > be >= 0.
> > Especially since dev_name(virt_devs[0]) == genpd:0:cpu0
> >
> > I guess it should still be possible to parse the required-opps manually here,
> > by iterating the OF nodes, however, we won't be able to use the CPU's struct
> > opp_table (which is the nice representation of the OF nodes).
> >
> > Any suggestions?
>
> --
> viresh

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