summaryrefslogtreecommitdiff
path: root/drivers/thermal/tango_thermal.c
diff options
context:
space:
mode:
Diffstat (limited to 'drivers/thermal/tango_thermal.c')
-rw-r--r--drivers/thermal/tango_thermal.c109
1 files changed, 109 insertions, 0 deletions
diff --git a/drivers/thermal/tango_thermal.c b/drivers/thermal/tango_thermal.c
new file mode 100644
index 000000000..70e0d9f40
--- /dev/null
+++ b/drivers/thermal/tango_thermal.c
@@ -0,0 +1,109 @@
+#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(0, priv->base + TEMPSI_CFG);
+ writel(CMD_ON, priv->base + TEMPSI_CMD);
+
+ tzdev = devm_thermal_zone_of_sensor_register(&pdev->dev, 0, priv, &ops);
+ return PTR_ERR_OR_ZERO(tzdev);
+}
+
+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");