thermal: add temperature sensor support for tango SoC

* Tango Thermal

The SMP8758 SoC includes 3 instances of this temperature sensor

(in the CPU, video decoder, and PCIe controller).

Required properties:

- #thermal-sensor-cells: Should be 0 (see thermal.txt)

- compatible: "sigma,smp8758-thermal"

- reg: Address range of the thermal registers

Example:

	cpu_temp: thermal@920100 {

		#thermal-sensor-cells = <0>;

		compatible = "sigma,smp8758-thermal";

		reg = <0x920100 12>;

	};

source "drivers/thermal/st/Kconfig"

endmenu

config TANGO_THERMAL

	tristate "Tango thermal management"

	depends on ARCH_TANGO || COMPILE_TEST

	help

	  Enable the Tango thermal driver, which supports the primitive

	  temperature sensor embedded in Tango chips since the SMP8758.

	  This sensor only generates a 1-bit signal to indicate whether

	  the die temperature exceeds a programmable threshold.

source "drivers/thermal/tegra/Kconfig"

config QCOM_SPMI_TEMP_ALARM

obj-$(CONFIG_DOVE_THERMAL)  	+= dove_thermal.o

obj-$(CONFIG_DB8500_THERMAL)	+= db8500_thermal.o

obj-$(CONFIG_ARMADA_THERMAL)	+= armada_thermal.o

obj-$(CONFIG_TANGO_THERMAL)	+= tango_thermal.o

obj-$(CONFIG_IMX_THERMAL)	+= imx_thermal.o

obj-$(CONFIG_DB8500_CPUFREQ_COOLING)	+= db8500_cpufreq_cooling.o

obj-$(CONFIG_INTEL_POWERCLAMP)	+= intel_powerclamp.o

#include <linux/io.h>

#include <linux/delay.h>

#include <linux/module.h>

#include <linux/thermal.h>

#include <linux/platform_device.h>

/*

 * According to a data sheet draft, "this temperature sensor uses a bandgap

 * type of circuit to compare a voltage which has a negative temperature

 * coefficient with a voltage that is proportional to absolute temperature.

 * A resistor bank allows 41 different temperature thresholds to be selected

 * and the logic output will then indicate whether the actual die temperature

 * lies above or below the selected threshold."

 */

#define TEMPSI_CMD	0

#define TEMPSI_RES	4

#define TEMPSI_CFG	8

#define CMD_OFF		0

#define CMD_ON		1

#define CMD_READ	2

#define IDX_MIN		15

#define IDX_MAX		40

struct tango_thermal_priv {

	void __iomem *base;

	int thresh_idx;

};

static bool temp_above_thresh(void __iomem *base, int thresh_idx)

{

	writel(CMD_READ | thresh_idx << 8, base + TEMPSI_CMD);

	usleep_range(10, 20);

	writel(CMD_READ | thresh_idx << 8, base + TEMPSI_CMD);

	return readl(base + TEMPSI_RES);

}

static int tango_get_temp(void *arg, int *res)

{

	struct tango_thermal_priv *priv = arg;

	int idx = priv->thresh_idx;

	if (temp_above_thresh(priv->base, idx)) {

		/* Search upward by incrementing thresh_idx */

		while (idx < IDX_MAX && temp_above_thresh(priv->base, ++idx))

			cpu_relax();

		idx = idx - 1; /* always return lower bound */

	} else {

		/* Search downward by decrementing thresh_idx */

		while (idx > IDX_MIN && !temp_above_thresh(priv->base, --idx))

			cpu_relax();

	}

	*res = (idx * 9 / 2 - 38) * 1000; /* millidegrees Celsius */

	priv->thresh_idx = idx;

	return 0;

}

static const struct thermal_zone_of_device_ops ops = {

	.get_temp	= tango_get_temp,

};

static int tango_thermal_probe(struct platform_device *pdev)

{

	struct resource *res;

	struct tango_thermal_priv *priv;

	struct thermal_zone_device *tzdev;

	priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);

	if (!priv)

		return -ENOMEM;

	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);

	priv->base = devm_ioremap_resource(&pdev->dev, res);

	if (IS_ERR(priv->base))

		return PTR_ERR(priv->base);

	priv->thresh_idx = IDX_MIN;

	writel(CMD_ON, priv->base + TEMPSI_CMD);

	tzdev = devm_thermal_zone_of_sensor_register(&pdev->dev, 0, priv, &ops);

	if (IS_ERR(tzdev))

		return PTR_ERR(tzdev);

	return 0;

}

static const struct of_device_id tango_sensor_ids[] = {

	{

		.compatible = "sigma,smp8758-thermal",

	},

	{ /* sentinel */ }

};

static struct platform_driver tango_thermal_driver = {

	.probe	= tango_thermal_probe,

	.driver	= {

		.name		= "tango-thermal",

		.of_match_table	= tango_sensor_ids,

	},

};

module_platform_driver(tango_thermal_driver);

MODULE_LICENSE("GPL");

MODULE_AUTHOR("Sigma Designs");

MODULE_DESCRIPTION("Tango temperature sensor");