linux-kernel - Re: [PATCH v1 3/3] PM / AVS: rockchip-cpu-avs: add driver handling Rockchip cpu avs

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Date:   Tue, 23 Aug 2016 12:10:27 +0800
From:   Finley Xiao <finley.xiao@...k-chips.com>
To:     Rob Herring <robh@...nel.org>
Cc:     srinivas.kandagatla@...aro.org, maxime.ripard@...e-electrons.com,
        heiko@...ech.de, frowand.list@...il.com, sre@...nel.org,
        dbaryshkov@...il.com, dwmw2@...radead.org, mark.rutland@....com,
        khilman@...nel.org, nm@...com, rjw@...ysocki.net,
        viresh.kumar@...aro.org, sboyd@...eaurora.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-rockchip@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        wxt@...k-chips.com, jay.xu@...k-chips.com,
        rocky.hao@...k-chips.com, tim.chen@...k-chips.com,
        tony.xie@...k-chips.com, ulysses.huang@...k-chips.com,
        lin.huang@...k-chips.com
Subject: Re: [PATCH v1 3/3] PM / AVS: rockchip-cpu-avs: add driver handling
 Rockchip cpu avs



在 2016/8/19 21:36, Rob Herring 写道:
> On Tue, Aug 16, 2016 at 10:38:59AM +0800, Finlye Xiao wrote:
>> From: Finley Xiao <finley.xiao@...k-chips.com>
>>
>> This patch supports adjusting opp's voltage according to leakage
>>
>> Signed-off-by: Finley Xiao <finley.xiao@...k-chips.com>
>> ---
>>   .../devicetree/bindings/power/rockchip-cpu-avs.txt |  37 +++
>>   drivers/power/avs/Kconfig                          |   8 +
>>   drivers/power/avs/Makefile                         |   1 +
>>   drivers/power/avs/rockchip-cpu-avs.c               | 314 +++++++++++++++++++++
>>   4 files changed, 360 insertions(+)
>>   create mode 100644 Documentation/devicetree/bindings/power/rockchip-cpu-avs.txt
>>   create mode 100644 drivers/power/avs/rockchip-cpu-avs.c
>>
>> diff --git a/Documentation/devicetree/bindings/power/rockchip-cpu-avs.txt b/Documentation/devicetree/bindings/power/rockchip-cpu-avs.txt
>> new file mode 100644
>> index 0000000..90f6b08
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/power/rockchip-cpu-avs.txt
>> @@ -0,0 +1,37 @@
>> +Rockchip cpu avs device tree bindings
>> +-------------------------------------
>> +
>> +Under the same frequency, the operating voltage tends to decrease with
>> +increasing leakage. so it is necessary to adjust opp's voltage according
>> +to leakage for power.
>> +
>> +
>> +Required properties:
>> +- compatible: Should be one of the following.
>> +  - "rockchip,rk3399-cpu-avs" - for RK3399 SoCs.
>> +- leakage-volt-<name>: Named leakage-volt property. At runtime, the
>> +  platform can find a cpu's cluster_id according to it's cpu_id and match
>> +  leakage-volt-<name> property. The property is an array of 3-tuples
>> +  items, and each item consists of leakage and voltage like
>> +  <min-leakage-mA max-leakage-mA vol-uV>.
>> +	min-leakage: minimum leakage in mA.
>> +	max-leakage: maximum leakage in mA.
>> +	vol: voltage in microvolt.
> How do you determine these values? When do they vary?

How do you determine these values?

run antutu-benchmark
leakage     freq 	min_volt
30mA 	    1608MHz 	1025mV
40mA 	    1608MHz 	1000mV
50mA 	    1608MHz 	975mV

 From the table, we see the min_volt decrease with increasing leakage.
So we can set the default opp-microvolt 1025mV for 1608MHz,
and add an leakage_volt_cluster0 property as follows.
leakage_volt_cluster0 = <
		/*  min(mA)   max(mA)    volt(uV)*/
		    0         40        0
		    41        50        (-25000)
		    51        254       (-50000)
>;
If the leakage is between 41mA and 50mA，the opp-microvolt will subtract 25mV。
If the leakage is between 41mA and 50mA，the opp-microvolt will subtract 50mV。
  
When do they vary?

 From the code,
cpufreq_online
--cpufreq_driver->init(policy);  /* add new opp table */
--blocking_notifier_call_chain(&cpufreq_policy_notifier_list,
CPUFREQ_START, policy);
--cpufreq_init_policy
----cpufreq_set_policy
--------__cpufreq_governor(policy, CPUFREQ_GOV_START);

The cpu's opp table is added in the init function(cpufreq_init)，and I will
register a cpufreq notifier, once the first cpu of cluster is onlined,
my notifer will be called, and if the event is CPUFREQ_START，it will modify
the opp-microvolt according to leakage_volt_cluster0.

>> +
>> +Example:
>> +
>> +	cpu_avs: cpu-avs {
>> +		compatible = "rockchip,rk3399-cpu-avs";
> This isn't really a hardware block. For the same reasons we don't have
> cpufreq nodes. So I don't think this belongs in DT.

if I delete the compatible property like the thermal-zones node, is it allowed?
cpu_avs: cpu-avs {
	leakage_volt_cluster0 = <
		/*  min(mA)   max(mA)    volt(uV)*/
		    0         40        0
		    41        50        (-25000)
		    51        254       (-50000)
	>;
	leakage_volt_cluster1 = <
		/*  min(mA)   max(mA)    volt(uV)*/
		    0         40        0
		    41        50        (-25000)
		    51        254       (-50000)
	>;
}


>
> Rob
>
>
>

-- 
Finley