[PATCH V2 0/9] Implementation of Tegra Tachometer driver

[Rajkumar Rampelli]

The following patches adds support for PWM based Tegra Tachometer driver
which implements PWM capture interface to analyze the PWM signal of a
electronic fan and reports it in periods and duty cycles.

Added fan device attribute fan1_input in pwm-fan driver to monitor the
speed of fan in rotations per minute using PWM interface.
RPM of Fan will be exposed to user interface through HWMON sysfs interface
avialable at location: /sys/class/hwmon/hwmon0/fan1_input

Steps to validate Tachometer on Tegra186 SoC:
A. push modules pwm-tegra.ko, pwm-tegra-tachometer.ko and pwm-fan.ko to
   linux device using scp command.
   scp build/tegra186/drivers/pwm/pwm-tegra.ko ubuntu at 10.19.65.176:/tmp/
   scp build/tegra186/drivers/pwm/pwm-tegra-tachometer.ko ubuntu at 10.19.65.176:/tmp/
   scp build/tegra186/drivers/hwmon/pwm-fan.ko ubuntu at 10.19.65.176:/tmp/
B. On Linux device console, insert these modules using insmod command.
   insmod /tmp/pwm-tegra.ko
   insmod /tmp/pwm-tegra-tachometer.ko
   insmod /tmp/pwm-fan.ko
C. Read RPM value at below sysfs node
   cat /sys/calss/hwmon/hwmon0/fan1_input
D. Change the FAN speed using PWM sysfs interface. Follow below steps for the same:
   a. cd /sys/class/pwm/pwmchip0
   b. ls -la (make sure pwm controller is c340000.pwm)
      Output should be: device -> ../../../c340000.pwm
   c. echo 0 > export
   d. cd pwmchip0:0
   e. echo 8000 > period
   f. echo 1 > enable
   g. echo 8000 > duty_cycle # change duty_cycles from 0 to 8000 for FAN speed variation
   h. cat /sys/calss/hwmon/hwmon0/fan1_input
   i. echo 4000 > duty_cycle
   h. cat /sys/calss/hwmon/hwmon0/fan1_input
   i. echo 2000 > duty_cycle
   h. cat /sys/calss/hwmon/hwmon0/fan1_input
   i. echo 0 > duty_cycle
   h. cat /sys/calss/hwmon/hwmon0/fan1_input

Rajkumar Rampelli (9):
  pwm: core: Add support for PWM HW driver with pwm capture only
  arm64: tegra: Add PWM controller on Tegra186 soc
  dt-bindings: Tegra186 tachometer device tree bindings
  arm64: tegra: Add Tachometer Controller on Tegra186
  pwm: tegra: Add PWM based Tachometer driver
  arm64: tegra: Add pwm based fan support on Tegra186
  hwmon: pwm-fan: add sysfs node to read rpm of fan
  arm64: defconfig: enable Nvidia Tegra Tachometer as a module
  arm64: defconfig: enable pwm-fan as a loadable module

 .../bindings/pwm/pwm-tegra-tachometer.txt          |  31 +++
 arch/arm64/boot/dts/nvidia/tegra186-p2771-0000.dts |   5 +
 arch/arm64/boot/dts/nvidia/tegra186.dtsi           |  28 ++
 arch/arm64/configs/defconfig                       |   2 +
 drivers/hwmon/pwm-fan.c                            |  23 ++
 drivers/pwm/Kconfig                                |  10 +
 drivers/pwm/Makefile                               |   1 +
 drivers/pwm/core.c                                 |  21 +-
 drivers/pwm/pwm-tegra-tachometer.c                 | 303 +++++++++++++++++++++
 9 files changed, 418 insertions(+), 6 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/pwm/pwm-tegra-tachometer.txt
 create mode 100644 drivers/pwm/pwm-tegra-tachometer.c

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2.1.4