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

[Finley Xiao]

å 2016/8/19 21:36, Rob Herring åé:
> On Tue, Aug 16, 2016 at 10:38:59AM +0800, Finlye Xiao wrote:
> > From: Finley Xiao <finley.xiao@xxxxxxxxxxxxxx>
> >
> > This patch supports adjusting opp's voltage according to leakage
> >
> > Signed-off-by: Finley Xiao <finley.xiao@xxxxxxxxxxxxxx>
> > ---
> >   .../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 50mAïthe opp-microvolt will subtract 25mVã
If the leakage is between 41mA and 50mAïthe opp-microvolt will subtract 50mVã
 
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)ïand 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_STARTïit 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