tango_thermal.c
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#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 void tango_thermal_init(struct tango_thermal_priv *priv)
{
writel(0, priv->base + TEMPSI_CFG);
writel(CMD_ON, priv->base + TEMPSI_CMD);
}
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);
platform_set_drvdata(pdev, priv);
priv->thresh_idx = IDX_MIN;
tango_thermal_init(priv);
tzdev = devm_thermal_zone_of_sensor_register(&pdev->dev, 0, priv, &ops);
return PTR_ERR_OR_ZERO(tzdev);
}
static int __maybe_unused tango_thermal_resume(struct device *dev)
{
tango_thermal_init(dev_get_drvdata(dev));
return 0;
}
static SIMPLE_DEV_PM_OPS(tango_thermal_pm, NULL, tango_thermal_resume);
static const struct of_device_id tango_sensor_ids[] = {
{
.compatible = "sigma,smp8758-thermal",
},
{ /* sentinel */ }
};
MODULE_DEVICE_TABLE(of, tango_sensor_ids);
static struct platform_driver tango_thermal_driver = {
.probe = tango_thermal_probe,
.driver = {
.name = "tango-thermal",
.of_match_table = tango_sensor_ids,
.pm = &tango_thermal_pm,
},
};
module_platform_driver(tango_thermal_driver);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Sigma Designs");
MODULE_DESCRIPTION("Tango temperature sensor");