therm-fan-est: Add support for Tmargin to drive fan

Why?
Tmargin method of fan control allows multiple groups of
therma-fan-est devices temperatures to be considered for
the fan control algorithm/fan curve. The limitation of the
existing max temp algorithm in therm-fan-est driver is that
devices with different fan curves cannot be accomodated in
the driver. In case, there are multple fan curves, the device
which has the steepest curve wins the algoritm. Hence, taking
the temperatures as a reference from their respective critical
temperatures and using that value to drive the fan will help in
accomodating both the devices' fan curves.

How?
* Calculate the effective crit temp of all the thermal zones
  during probe.
* In the polling cycles, calculate the effective temperatures
  of the individual groups and use the tmargin formula to
  calculate the current temperature.
* Since the Tmargin temp trip values are in reverse order, we
  need to use the reverse order in the pwm-fan dt profile.
* The hysterysis is subtracted from the temp in cooling scenario
  to avoid frequent switching at trip temps. Since the tmargin
  trip values are taken in the decending order, hysterysis temps
  in dt should be given as negative values.

Bug 200627962

Change-Id: Ideba4bfdb3d3306d1b4aff15093bcfac13d7bb86
Signed-off-by: Mantravadi Karthik <mkarthik@nvidia.com>
Reviewed-on: https://git-master.nvidia.com/r/c/linux-nvidia/+/2362354
Reviewed-by: automaticguardword <automaticguardword@nvidia.com>
Reviewed-by: Rajkumar Kasirajan <rkasirajan@nvidia.com>
Reviewed-by: Bibek Basu <bbasu@nvidia.com>
Reviewed-by: mobile promotions <svcmobile_promotions@nvidia.com>
Tested-by: Rajkumar Kasirajan <rkasirajan@nvidia.com>
Tested-by: mobile promotions <svcmobile_promotions@nvidia.com>
GVS: Gerrit_Virtual_Submit

1 files changed, 90 insertions, 0 deletions

diff --git a/Documentation/devicetree/bindings/misc/therm_est.txt b/Documentation/devicetree/bindings/misc/therm_est.txt
index 0dbcb147a..0538981a7 100644
--- a/Documentation/devicetree/bindings/misc/therm_est.txt
+++ b/Documentation/devicetree/bindings/misc/therm_est.txt
@@ -6,6 +6,8 @@ Properties :
  - tc1 : Coefficient 1 for thermal trend calculation.
  - tc2 : Coefficient 2 for thermal trend calculation.
  - node for subdev : Node for subdevice information. Required.
+ - use_tmargin : if tmargin algorithm should be used for calculating the
+   effective temp. Refer Tmargin section for more info.
 
 Properties in subdev node : Required.
  - subdev_names : list of strings. It contains list of the name of the therm
@@ -45,3 +47,91 @@ Example:
                         };
                 };
         };
+
+Tmargin Algorithm:
+The native max temp algorithm lacks support for accomodating multiple thermal
+fan curves. Tmargin algorithm solves this by calculating the effective
+temperature as a difference from critical temperature of the therm fan est
+group. This allows us to take a union of two fan curves and satisfy the needs
+of both the therm-fan-est groups.
+The algorithm use the effective temperature(crit_temp - sensor_reading) to
+drive the cooling device.
+
+Properties rules for therm-fan-est dt entry:
+ - use_tmargin : To use the tmargin feature.
+ - profiles : New profile tmargin should be defined and chosen as default.
+        * The trip temperatures need to be given only in ascending order for the
+          thermal framework to register therm-fan-est zone. Hence, the dt values
+          for active trip temps should be given in ascending values of tmargin
+          values.
+        * Hysterysis is used only in cooling scenario. Since tmargin is
+          considered as a diff wrt crit_Temp, hysterysis values should be taken
+          as -ve values.
+
+Properties rules for fan dt entry:
+ - profiles : New profile for tmargin should be defined and chosen as default.
+        * The trip temps are considered in a ascending order of tmargin temps.
+          Hence, the pwm values should be considered in a descending order of
+          pwms.
+        * active_steps - The tmargin trip values are considered in the ascending
+          order(hence actual trip temps will be in descending order), so the
+          pwm mapping should be in the reverse order starting from 255 for
+          index 0.
+
+Example :
+
+        thermal-fan-est {
+                compatible = "thermal-fan-est";
+                name = "thermal-fan-est";
+                status = "okay";
+                num_resources = <0>;
+                shared_data = <&thermal_fan_est_shared_data>;
+                trip_length = <10>;
+                use_tmargin;
+
+                profiles {
+                        default = "tmargin";
+                        quiet {
+                                active_trip_temps = <0 50000 63000 72000 81000
+                                                140000 150000 160000 170000 180000>;
+                                active_hysteresis = <0 18000 8000 8000 8000
+                                                0 0 0 0 0>;
+                        };
+                        cool {
+                                active_trip_temps = <0 35000 53000 62000 73000
+                                                140000 150000 160000 170000 180000>;
+                                active_hysteresis = <0 9000 8000 8000 9000
+                                                0 0 0 0 0>;
+                        };
+                        tmargin {
+                                active_trip_temps = <0 10000 15000 25000 35000
+                                                45000 55000 65000 75000 105000>;
+                                active_hysteresis = <0 0 0 0 (-3000)
+                                                (-4000) (-4000) 0 0 0>;
+                        };
+                };
+        };
+
+        pwm-fan {
+                compatible = "pwm-fan";
+                status = "okay";
+                #pwm-cells = <1>;
+                pwms = <&tegra_pwm4 0 45334>;
+                shared_data = <&pwm_fan_shared_data>;
+                profiles {
+                        default = "tmargin";
+                        quiet {
+                                state_cap = <8>;
+                                active_pwm = <0 60 90 120 150 180 210 240 255 255>;
+                        };
+                        cool {
+                                state_cap = <4>;
+                                active_pwm = <0 77 120 160 255 255 255 255 255 255>;
+                        };
+                        tmargin {
+                                state_cap = <0>;
+                                active_pwm = <255 255 240 210 180 150 120 90 60 0>;
+                        };
+                };
+        };
+