[PATCH-V2 0/5] bcm2835: add thermal driver

kernel at martin.sperl.org kernel at martin.sperl.org
Fri May 13 06:13:01 PDT 2016

From: Martin Sperl <kernel at martin.sperl.org>

Add a thermal driver for the TSENSE device of the bcm2835 SOC.

If the firmware enables the HW, then the configuration is not touched.
In case the firmware has not enabled the device, then we try to set
it up correctly (which unfortunately can not get tested).

It exposes temperature and a critical trip point
(using a hardcoded default of 80C or the temperature configured
in the control register by the firmware - reads as 0 currently)

The calibrations are (potentially) different for bcm2835, bcm2836
and bcm2837 and can get selected by the compatiblity property
in the device tree.

The driver also exposes the registers via debugfs.

Possible future enhancements:
* the device has the ability to trigger interrupts on reaching
  the programmed critical temperature.
  I have no knowledge which interrupt could be responsible
  for this on the ARM side, so if we get to know which irq
  it is we can implement that
* the device can also reset the HW after the trip point
  has been reached (also with some delay, so that corrective
  actions can get taken) - this is currently not enabled by the
  firmware, but could.
* we could define more trip points for THERMAL_TRIP_HOT
* make the trip point limits modifiable (ops.set_trip_temp)

 V1 -> V2: renamed dt-binding documentation file
       	   added specific settings depending on compatiblity
	   added trip point based on register
	   setting up ctrl-register if HW is not enabled by firmware
	     as per recommendation of Eric (untested)
	   check that clock frequency is in range
	     (1.9 - 5MHz - as per comment in clk-bcm2835.c)
 	   added driver to multi_v7_defconfig

Martin Sperl (5):
  dt: bindings: add thermal device driver for bcm2835
  thermal: bcm2835: add thermal driver for bcm2835 soc
  ARM: bcm2835: add thermal node to device-tree of bcm283x
  ARM: bcm2835: add thermal driver to default_config
  ARM: multi_v7_defconfig: bcm2835: add bcm2835-thermal driver

 .../bindings/thermal/brcm,bcm2835-thermal.txt      |  17 ++
 arch/arm/boot/dts/bcm283x.dtsi                     |   6 +
 arch/arm/configs/bcm2835_defconfig                 |   2 +
 arch/arm/configs/multi_v7_defconfig                |   1 +
 drivers/thermal/Kconfig                            |   5 +
 drivers/thermal/Makefile                           |   1 +
 drivers/thermal/bcm/Kconfig                        |   4 +
 drivers/thermal/bcm/Makefile                       |   1 +
 drivers/thermal/bcm/bcm2835_thermal.c              | 326 +++++++++++++++++++++
 9 files changed, 363 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/thermal/brcm,bcm2835-thermal.txt
 create mode 100644 drivers/thermal/bcm/Kconfig
 create mode 100644 drivers/thermal/bcm/Makefile
 create mode 100644 drivers/thermal/bcm/bcm2835_thermal.c


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