linux-kernel - Re: [PATCH 11/13] arm64: dts: qcom: qcs404: Add CPR and populate OPP table

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Date:   Tue, 16 Jul 2019 16:04:36 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Niklas Cassel <niklas.cassel@...aro.org>
Cc:     Andy Gross <agross@...nel.org>, linux-arm-msm@...r.kernel.org,
        jorge.ramirez-ortiz@...aro.org, sboyd@...nel.org,
        vireshk@...nel.org, bjorn.andersson@...aro.org,
        ulf.hansson@...aro.org, Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 11/13] arm64: dts: qcom: qcs404: Add CPR and populate OPP
 table

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
> [    3.126489] cpr_pd_attach_dev: dev_pm_opp_get_opp_count for dev: cpr@...8000: 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