staging: OMAP4+: thermal: introduce bandgap temperature sensor

In the System Control Module, OMAP supplies a voltage reference
and a temperature sensor feature that are gathered in the band
gap voltage and temperature sensor (VBGAPTS) module. The band
gap provides current and voltage reference for its internal
circuits and other analog IP blocks. The analog-to-digital
converter (ADC) produces an output value that is proportional
to the silicon temperature.

This patch provides a platform driver which expose this feature.
It is moduled as a MFD child of the System Control Module core
MFD driver.

This driver provides only APIs to access the device properties,
like temperature, thresholds and update rate.
Signed-off-by: Eduardo Valentin <eduardo.valentin@ti.com>
Signed-off-by: J Keerthy <j-keerthy@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/Kconfig

@@ -134,4 +134,6 @@ source "drivers/staging/gdm72xx/Kconfig"
 
 source "drivers/staging/csr/Kconfig"
 
+source "drivers/staging/omap-thermal/Kconfig"
+
 endif # STAGING

drivers/staging/Makefile

@@ -59,3 +59,4 @@ obj-$(CONFIG_USB_WPAN_HCD)	+= ozwpan/
 obj-$(CONFIG_USB_G_CCG)		+= ccg/
 obj-$(CONFIG_WIMAX_GDM72XX)	+= gdm72xx/
 obj-$(CONFIG_CSR_WIFI)		+= csr/
+obj-$(CONFIG_OMAP_BANDGAP)	+= omap-thermal/

drivers/staging/omap-thermal/Kconfig

+config OMAP_BANDGAP
+	tristate "Texas Instruments OMAP4+ temperature sensor driver"
+	depends on THERMAL
+	depends on ARCH_OMAP4 || SOC_OMAP5
+	help
+	  If you say yes here you get support for the Texas Instruments
+	  OMAP4460+ on die bandgap temperature sensor support. The register
+	  set is part of system control module.
+
+	  This includes alert interrupts generation and also the TSHUT
+	  support.

drivers/staging/omap-thermal/Makefile

+obj-$(CONFIG_OMAP_BANDGAP)	+= omap-thermal.o
+omap-thermal-y			:= omap-bandgap.o

drivers/staging/omap-thermal/TODO

+List of TODOs (by Eduardo Valentin)
+
+on omap-bandgap.c:
+- Rework locking
+- Improve driver code by adding usage of regmap-mmio
+- Test every exposed API to userland
+- Add support to hwmon
+- Review and revisit all API exposed
+- Revisit PM support
+- Revisit data structures and simplify them
+- Once SCM-core api settles, update this driver accordingly
+
+on omap-thermal-common.c/omap-thermal.h:
+- Revisit extrapolation constants for O4/O5
+- Revisit need for locking
+- Revisit trips and its definitions
+- Revisit trending
+
+on omap5-thermal.c
+- Add support for GPU cooling
+
+generally:
+- write Kconfig dependencies so that omap variants are covered
+- make checkpatch.pl and sparse happy
+- make sure this code works on OMAP4430, OMAP4460 and OMAP5430
+- update documentation
+
+Copy patches to Eduardo Valentin <eduardo.valentin@ti.com>

drivers/staging/omap-thermal/omap_bandgap.txt

+* Texas Instrument OMAP SCM bandgap bindings
+
+In the System Control Module, OMAP supplies a voltage reference
+and a temperature sensor feature that are gathered in the band
+gap voltage and temperature sensor (VBGAPTS) module. The band
+gap provides current and voltage reference for its internal
+circuits and other analog IP blocks. The analog-to-digital
+converter (ADC) produces an output value that is proportional
+to the silicon temperature.
+
+Required properties:
+- compatible : Should be:
+  - "ti,omap4460-control-bandgap" : for OMAP4460 bandgap
+  - "ti,omap5430-control-bandgap" : for OMAP5430 bandgap
+- interrupts : this entry should indicate which interrupt line
+the talert signal is routed to;
+Specific:
+- ti,tshut-gpio : this entry should be used to inform which GPIO
+line the tshut signal is routed to;
+
+Example:
+
+bandgap {
+	reg = <0x4a002260 0x4
+		0x4a00232C 0x4
+		0x4a002378 0x18>;
+	compatible = "ti,omap4460-control-bandgap";
+	interrupts = <0 126 4>; /* talert */
+	ti,tshut-gpio = <86>;
+};