mvf_adc: read temperature sensor and use hwmon interface

Use the hwmon interface to expose the internal temperature sensor
connected to the ADC. In order to calculate the temperature typical
values from the electrical data sheet has been taken.

Read the sensor using sysfs:
$ cat /sys/class/hwmon/hwmon0/device/temp1_input
47282

Note: there are two hwmon devices exposed. Those are the two ADC,
however, both ADC connect to the same temperature sensor.
Essentially, the user can choose which ADC to use to read the
temperature sensor.

1 files changed, 96 insertions, 1 deletions

diff --git a/drivers/misc/mvf_adc.c b/drivers/misc/mvf_adc.c
index 5935d507451a..662d76667bdc 100644
--- a/drivers/misc/mvf_adc.c
+++ b/drivers/misc/mvf_adc.c
@@ -25,6 +25,8 @@
 #include <linux/mvf_adc.h>
 #include <linux/device.h>
 #include <linux/cdev.h>
+#include <linux/hwmon.h>
+#include <linux/hwmon-sysfs.h>
 
 #define DRIVER_NAME "mvf-adc"
 #define DRV_VERSION "1.2"
@@ -52,6 +54,7 @@ static DECLARE_COMPLETION(adc_tsi);
 
 struct adc_device {
 	struct platform_device	*pdev;
+	struct device 		*hwmon_dev;
 	struct clk		*clk;
 	struct adc_client	*cur;
 	void __iomem		*regs;
@@ -526,6 +529,79 @@ int mvf_adc_register_and_convert(unsigned int adc, unsigned char channel)
 }
 EXPORT_SYMBOL(mvf_adc_register_and_convert);
 
+/* Temperature sensor (hwmon) */
+
+static ssize_t adc_show_temp(struct device *dev,
+			       struct device_attribute *dev_attr, char *buf)
+{
+	struct adc_device *adc_dev = dev_get_drvdata(dev);
+	struct adc_client *client;
+	unsigned char channel = 26;
+	int temperature;
+	int ret;
+
+	struct adc_feature feature = {
+		.channel = ADC26,
+		.clk_sel = ADCIOC_BUSCLK_SET,
+		.clk_div_num = 1,
+		.res_mode = 12,
+		.sam_time = 6,
+		.lp_con = ADCIOC_LPOFF_SET,
+		.hs_oper = ADCIOC_HSOFF_SET,
+		.vol_ref = ADCIOC_VR_VREF_SET,
+		.tri_sel = ADCIOC_SOFTTS_SET,
+		.ha_sel = ADCIOC_HA_SET,
+		.ha_sam = 8,
+		.do_ena = ADCIOC_DOEOFF_SET,
+		.ac_ena = ADCIOC_ADACKENOFF_SET,
+		.dma_ena = ADCIDC_DMAOFF_SET,
+		.cc_ena = ADCIOC_CCEOFF_SET,
+		.compare_func_ena = ADCIOC_ACFEOFF_SET,
+		.range_ena = ADCIOC_ACRENOFF_SET,
+		.greater_ena = ADCIOC_ACFGTOFF_SET,
+		.result0 = 0,
+		.result1 = 0,
+	};
+
+	/* Initialize device */
+	adc_initiate(adc_dev);
+	ret = adc_set(adc_dev, &feature);
+	if (ret)
+		return ret;
+
+	/* Register client... */
+	client = adc_register(adc_dev->pdev, channel);
+	if (!client)
+		return -ENOMEM;
+
+	/* Do the ADC convertion of the temperature channel */
+	temperature = adc_convert_wait(adc_dev, channel);
+
+	/*
+	 * Calculate in degree celsius times 1000)
+	 * Using sensor slope of 1.84 mV/°C and
+	 * V at 25°C of 696mv
+	 */
+	temperature = 25000 - (temperature - 864) * 1000000 / 1840;
+
+	/* Free client */
+	kfree(client);
+
+	return sprintf(buf, "%d\n", temperature);
+}
+
+static SENSOR_DEVICE_ATTR(temp1_input, S_IRUGO, adc_show_temp, NULL, 0);
+
+static struct attribute *mvf_adc_attributes[] = {
+	&sensor_dev_attr_temp1_input.dev_attr.attr,
+	NULL
+};
+
+static const struct attribute_group mvf_adc_group = {
+	.attrs = mvf_adc_attributes,
+};
+
+
 static int adc_open(struct inode *inode, struct file *file)
 {
 	struct adc_device *dev = container_of(inode->i_cdev,
@@ -699,13 +775,25 @@ static int __devinit adc_probe(struct platform_device *pdev)
 	/* Save device structure by Platform device ID for touch */
 	adc_devices[pdev->id] = adc;
 
+	/* Register temperature sensor */
+	ret = sysfs_create_group(&pdev->dev.kobj, &mvf_adc_group);
+	if (ret < 0)
+		goto err_clk;
+
+	adc->hwmon_dev = hwmon_device_register(&pdev->dev);
+	if (IS_ERR(adc->hwmon_dev)) {
+		ret = PTR_ERR(adc->hwmon_dev);
+		dev_err(dev, "class registration failed (%d)\n", ret);
+		goto err_sysfs;
+	}
+
 	/* Create character device for ADC */
 	cdev_init(&adc->cdev, &adc_fops);
 	adc->cdev.owner = THIS_MODULE;
 	devt = MKDEV(mvf_adc_major, pdev->id);
 	ret = cdev_add(&adc->cdev, devt, 1);
 	if (ret < 0)
-		goto err_clk;
+		goto err_sysfs;
 
 	adc->dev = device_create(adc_class, &pdev->dev, devt,
 			NULL, "mvf-adc.%d", pdev->id);
@@ -724,6 +812,9 @@ static int __devinit adc_probe(struct platform_device *pdev)
 err_cdev:
 	cdev_del(&adc->cdev);
 
+err_sysfs:
+	sysfs_remove_group(&pdev->dev.kobj, &mvf_adc_group);
+
 err_clk:
 	clk_put(adc->clk);
 
@@ -743,8 +834,12 @@ static int __devexit adc_remove(struct platform_device *pdev)
 
 	dev_info(dev, "remove adc driver\n");
 
+	hwmon_device_unregister(adc->hwmon_dev);
+	sysfs_remove_group(&pdev->dev.kobj, &mvf_adc_group);
+
 	device_destroy(adc_class, adc->dev->devt);
 	cdev_del(&adc->cdev);
+
 	iounmap(adc->regs);
 	free_irq(adc->irq, adc);
 	clk_disable(adc->clk);