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

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Date:   Tue, 07 Aug 2018 12:24:14 -0700
From:   skannan@...eaurora.org
To:     Sudeep Holla <sudeep.holla@....com>
Cc:     Stephen Boyd <sboyd@...nel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Taniya Das <tdas@...eaurora.org>,
        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 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