110 lines
2.7 KiB
C
110 lines
2.7 KiB
C
#include <linux/io.h>
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#include <linux/delay.h>
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#include <linux/module.h>
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#include <linux/thermal.h>
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#include <linux/platform_device.h>
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/*
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* According to a data sheet draft, "this temperature sensor uses a bandgap
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* type of circuit to compare a voltage which has a negative temperature
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* coefficient with a voltage that is proportional to absolute temperature.
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* A resistor bank allows 41 different temperature thresholds to be selected
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* and the logic output will then indicate whether the actual die temperature
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* lies above or below the selected threshold."
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*/
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#define TEMPSI_CMD 0
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#define TEMPSI_RES 4
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#define TEMPSI_CFG 8
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#define CMD_OFF 0
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#define CMD_ON 1
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#define CMD_READ 2
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#define IDX_MIN 15
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#define IDX_MAX 40
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struct tango_thermal_priv {
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void __iomem *base;
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int thresh_idx;
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};
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static bool temp_above_thresh(void __iomem *base, int thresh_idx)
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{
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writel(CMD_READ | thresh_idx << 8, base + TEMPSI_CMD);
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usleep_range(10, 20);
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writel(CMD_READ | thresh_idx << 8, base + TEMPSI_CMD);
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return readl(base + TEMPSI_RES);
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}
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static int tango_get_temp(void *arg, int *res)
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{
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struct tango_thermal_priv *priv = arg;
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int idx = priv->thresh_idx;
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if (temp_above_thresh(priv->base, idx)) {
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/* Search upward by incrementing thresh_idx */
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while (idx < IDX_MAX && temp_above_thresh(priv->base, ++idx))
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cpu_relax();
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idx = idx - 1; /* always return lower bound */
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} else {
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/* Search downward by decrementing thresh_idx */
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while (idx > IDX_MIN && !temp_above_thresh(priv->base, --idx))
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cpu_relax();
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}
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*res = (idx * 9 / 2 - 38) * 1000; /* millidegrees Celsius */
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priv->thresh_idx = idx;
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return 0;
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}
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static const struct thermal_zone_of_device_ops ops = {
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.get_temp = tango_get_temp,
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};
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static int tango_thermal_probe(struct platform_device *pdev)
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{
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struct resource *res;
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struct tango_thermal_priv *priv;
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struct thermal_zone_device *tzdev;
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priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
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if (!priv)
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return -ENOMEM;
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res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
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priv->base = devm_ioremap_resource(&pdev->dev, res);
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if (IS_ERR(priv->base))
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return PTR_ERR(priv->base);
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priv->thresh_idx = IDX_MIN;
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writel(0, priv->base + TEMPSI_CFG);
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writel(CMD_ON, priv->base + TEMPSI_CMD);
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tzdev = devm_thermal_zone_of_sensor_register(&pdev->dev, 0, priv, &ops);
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return PTR_ERR_OR_ZERO(tzdev);
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}
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static const struct of_device_id tango_sensor_ids[] = {
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{
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.compatible = "sigma,smp8758-thermal",
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},
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{ /* sentinel */ }
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};
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static struct platform_driver tango_thermal_driver = {
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.probe = tango_thermal_probe,
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.driver = {
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.name = "tango-thermal",
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.of_match_table = tango_sensor_ids,
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},
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};
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module_platform_driver(tango_thermal_driver);
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MODULE_LICENSE("GPL");
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MODULE_AUTHOR("Sigma Designs");
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MODULE_DESCRIPTION("Tango temperature sensor");
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