bcm2835: add thermal driver

From: Martin Sperl <[email protected]>

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)

Changelog:
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

--
2.1.4

From: Martin Sperl <[email protected]>

Add documentation for bcm2835 SOC thermal sensor.

Changelog:
V1 -> V2: renamed file to follow naming conventions

---
 .../bindings/thermal/brcm,bcm2835-thermal.txt           | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/thermal/brcm,bcm2835-thermal.txt

new file mode 100644
index 0000000..09de164
@@ -0,0 +1,17 @@
+Binding for Thermal Sensor driver for BCM2835 SoCs.
+
+Required parameters:
+-------------------
+
+compatible: 	should be one of: "brcm,bcm2835-thermal",
+		"brcm,bcm2836-thermal" or "brcm,bcm2837-thermal"
+reg:		Address range of the thermal registers.
+clocks: 	Phandle of the clock used by the thermal sensor.
+
+Example:
+
+thermal: thermal at 0x7e212000 {
+	compatible = "brcm,bcm2835-thermal";
+	reg = <0x7e212000 0x8>;
+	clocks = <&clocks BCM2835_CLOCK_TSENS>;
+};

--
2.1.4

From: Martin Sperl <[email protected]>

Add basic thermal driver for bcm2835 SOC.

This driver currently relies on the firmware setting up the tsense HW block and does not set it up itself.

ChangeLog:
V1 -> V2: 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)

---
 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 ++++++++++++++++++++++++++++++++++
 5 files changed, 337 insertions(+)
 create mode 100644 drivers/thermal/bcm/Kconfig
 create mode 100644 drivers/thermal/bcm/Makefile
 create mode 100644 drivers/thermal/bcm/bcm2835_thermal.c

index 3c3dc4a..5b63d45 100644
@@ -383,6 +383,11 @@ config MTK_THERMAL
 	  Enable this option if you want to have support for thermal management
 	  controller present in Mediatek SoCs
 
+menu "Broadcom thermal drivers"
+depends on ARCH_BCM || COMPILE_TEST
+source "drivers/thermal/bcm/Kconfig"
+endmenu
+
 menu "Texas Instruments thermal drivers"
 depends on ARCH_HAS_BANDGAP || COMPILE_TEST
 depends on HAS_IOMEM

index 8e9cbc3..6df1aa3 100644
@@ -49,3 +49,4 @@ obj-$(CONFIG_ST_THERMAL)	+= st/
 obj-$(CONFIG_TEGRA_SOCTHERM)	+= tegra_soctherm.o
 obj-$(CONFIG_HISI_THERMAL)     += hisi_thermal.o
 obj-$(CONFIG_MTK_THERMAL)	+= mtk_thermal.o
+obj-y				+= bcm/

new file mode 100644
index 0000000..62245ae
@@ -0,0 +1,4 @@
+config BCM2835_THERMAL
+       tristate "Thermal sensors on bcm2835 SoC"
+       help
+         Support for thermal sensors on Broadcom bcm2835 SoCs.

new file mode 100644
index 0000000..13456d2
@@ -0,0 +1 @@
+obj-$(CONFIG_BCM2835_THERMAL)		:= bcm2835_thermal.o

2.1.4

From: Martin Sperl <[email protected]>

Add the node for the thermal sensor of the bcm2835-soc to the device tree.

---
 arch/arm/boot/dts/bcm283x.dtsi | 6 ++++++
 1 file changed, 6 insertions(+)

index 8aaf193..2b5cbc6 100644
@@ -153,6 +153,12 @@
 			status = "disabled";
 		};
 
+		thermal: thermal at 0x7e212000 {
+			compatible = "brcm,bcm2835-thermal";
+			reg = <0x7e212000 0x8>;
+			clocks = <&clocks BCM2835_CLOCK_TSENS>;
+		};
+
 		aux: aux at 0x7e215000 {
 			compatible = "brcm,bcm2835-aux";
 			#clock-cells = <1>;

2.1.4

From: Martin Sperl <[email protected]>

Add the thermal driver to list of compiled modules in the default config for bcm2835.

---
 arch/arm/configs/bcm2835_defconfig | 2 ++
 1 file changed, 2 insertions(+)

index 1ef69fc..f254d6b 100644
@@ -71,6 +71,8 @@ CONFIG_SPI_BCM2835=y
 CONFIG_SPI_BCM2835AUX=y
 CONFIG_GPIO_SYSFS=y
 # CONFIG_HWMON is not set
+CONFIG_THERMAL=y
+CONFIG_BCM2835_THERMAL=y
 CONFIG_WATCHDOG=y
 CONFIG_BCM2835_WDT=y
 CONFIG_FB=y

2.1.4

From: Martin Sperl <[email protected]>

Add the thermal driver to list of compiled modules in multi_v7_defconfig.

---
 arch/arm/configs/multi_v7_defconfig | 1 +
 1 file changed, 1 insertion(+)

index 2823490..5f0f5a3 100644
@@ -422,6 +422,7 @@ CONFIG_CPU_THERMAL=y
 CONFIG_ROCKCHIP_THERMAL=y
 CONFIG_RCAR_THERMAL=y
 CONFIG_ARMADA_THERMAL=y
+CONFIG_BCM2835_THERMAL=y
 CONFIG_DAVINCI_WATCHDOG=m
 CONFIG_EXYNOS_THERMAL=m
 CONFIG_ST_THERMAL_SYSCFG=y

2.1.4

Not necessarily, but as most other drivers in this context are built in this one was added as such as well.

If the policy is different, then I can change it...