linux-kernel - Re: [PATCH v7 1/2] dt-bindings: cpufreq: Introduce QCOM CPUFREQ Firmware bindings

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Date:   Wed, 8 Aug 2018 08:16:01 +0530
From:   Taniya Das <tdas@...eaurora.org>
To:     skannan@...eaurora.org, Sudeep Holla <sudeep.holla@....com>
Cc:     Stephen Boyd <sboyd@...nel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        Rajendra Nayak <rnayak@...eaurora.org>,
        Amit Nischal <anischal@...eaurora.org>,
        devicetree@...r.kernel.org, robh@...nel.org,
        amit.kucheria@...aro.org, evgreen@...gle.com
Subject: Re: [PATCH v7 1/2] dt-bindings: cpufreq: Introduce QCOM CPUFREQ
 Firmware bindings



On 8/8/2018 12:54 AM, skannan@...eaurora.org wrote:
> On 2018-08-07 04:12, Sudeep Holla wrote:
>> On Mon, Aug 06, 2018 at 01:54:24PM -0700, skannan@...eaurora.org wrote:
>>> On 2018-08-03 16:46, Stephen Boyd wrote:
>>> >Quoting Taniya Das (2018-07-24 03:42:49)
>>> >>diff --git
>>> >>a/Documentation/devicetree/bindings/cpufreq/cpufreq-qcom-hw.txt
>>> >>b/Documentation/devicetree/bindings/cpufreq/cpufreq-qcom-hw.txt
>>> >>new file mode 100644
>>> >>index 0000000..22d4355
>>> >>--- /dev/null
>>> >>+++ b/Documentation/devicetree/bindings/cpufreq/cpufreq-qcom-hw.txt
>>> >>@@ -0,0 +1,172 @@
>>> >[...]
>>> >>+
>>> >>+               CPU7: cpu@700 {
>>> >>+                       device_type = "cpu";
>>> >>+                       compatible = "qcom,kryo385";
>>> >>+                       reg = <0x0 0x700>;
>>> >>+                       enable-method = "psci";
>>> >>+                       next-level-cache = <&L2_700>;
>>> >>+                       qcom,freq-domain = <&freq_domain_table1>;
>>> >>+                       L2_700: l2-cache {
>>> >>+                               compatible = "cache";
>>> >>+                               next-level-cache = <&L3_0>;
>>> >>+                       };
>>> >>+               };
>>> >>+       };
>>> >>+
>>> >>+       qcom,cpufreq-hw {
>>> >>+               compatible = "qcom,cpufreq-hw";
>>> >>+
>>> >>+               clocks = <&rpmhcc RPMH_CXO_CLK>;
>>> >>+               clock-names = "xo";
>>> >>+
>>> >>+               #address-cells = <2>;
>>> >>+               #size-cells = <2>;
>>> >>+               ranges;
>>> >>+               freq_domain_table0: freq_table0 {
>>> >>+                       reg = <0 0x17d43000 0 0x1400>;
>>> >>+               };
>>> >>+
>>> >>+               freq_domain_table1: freq_table1 {
>>> >>+                       reg = <0 0x17d45800 0 0x1400>;
>>> >>+               };
>>> >
>>> >Sorry, this is just not proper DT design. The whole node should have a
>>> >reg property, and it should contain two (or three if we're handling the
>>> >L3 clk domain?) different offsets for the different power clusters. The
>>> >problem seems to still be that we don't have a way to map the CPUs to
>>> >the clk domains they're in provided by this hardware block. Making
>>> >subnodes is not the solution.
>>>
>>> The problem is mapping clock domains to logical CPUs that CPUfreq 
>>> uses. The
>>> physical CPU to logical CPU mapping can be changed by the kernel (even
>>> through DT if I'm not mistaken). So we need to have a way to tell in DT
>>> which physical CPUs are connected to which CPU freq clock domain.
>>>
>>
>> How about passing CPU freq clock domain id as along with phandle in
>> qcom,freq-domain ?
> 
> Now sure what you mean here. There's no such this as CPUfreq clock 
> domain id. It has policies that are made up of logical CPU numbers. 
> Logical CPU is not something that you can fix in DT.
> 
> -Saravana

Sudeep,

Earlier the design was the freq_domain would take the CPU phandles

freq_domain:
   cpus = <&cpu0 &cpu1....>;

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