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Subject[PATCH] thermal: add generic IIO channel thermal sensor driver
Date
This driver is a generic method for using IIO ADC channels as thermal
sensors.

Signed-off-by: Courtney Cavin <courtney.cavin@sonymobile.com>
---
.../devicetree/bindings/thermal/iio-thermal.txt | 46 +++++
drivers/thermal/Kconfig | 13 ++
drivers/thermal/Makefile | 1 +
drivers/thermal/iio_thermal.c | 207 +++++++++++++++++++++
4 files changed, 267 insertions(+)
create mode 100644 Documentation/devicetree/bindings/thermal/iio-thermal.txt
create mode 100644 drivers/thermal/iio_thermal.c

diff --git a/Documentation/devicetree/bindings/thermal/iio-thermal.txt b/Documentation/devicetree/bindings/thermal/iio-thermal.txt
new file mode 100644
index 0000000..3be11b6
--- /dev/null
+++ b/Documentation/devicetree/bindings/thermal/iio-thermal.txt
@@ -0,0 +1,46 @@
+Generic IIO channel thermal sensor bindings
+
+compatible:
+ Usage: required
+ Type: string
+ Desc: compatible string, must be "iio-thermal"
+
+conversion-method:
+ Usage: required
+ Type: string
+ Desc: How to convert IIO voltage values to temperature, one of:
+ "interpolation" - interpolate between values in lookup table
+ "scalar" - use values as multiplier and divisor
+
+conversion-values:
+ Usage: required
+ Type: u32 array, 2-tuples
+ Desc: lookup table for conversion, for conversion-method:
+ "interpolation" - 2-tuples of < uV mK >; micro-volts to
+ milli-kelvin; table must ascend
+ "scalar" - single scalar 2-tuple as < M D >; where:
+ mK = uV * M / D
+
+io-channels:
+ Usage: required
+ Type: prop-encoded-array
+ Desc: See bindings/iio/iio-bindings.txt; must be a voltage channel
+
+Example:
+
+vadc: some_vadc {
+ compatible = "...";
+ #io-channel-cells = <1>;
+};
+
+iio-thermal {
+ compatible = "iio-thermal";
+ io-channels = <&vadc 0>;
+ conversion-method = "interpolation";
+ conversion-values = <
+ 30000 398200
+ 385000 318200
+ 1738000 233200
+ >;
+};
+
diff --git a/drivers/thermal/Kconfig b/drivers/thermal/Kconfig
index 35c0664..f83a8e8 100644
--- a/drivers/thermal/Kconfig
+++ b/drivers/thermal/Kconfig
@@ -114,6 +114,19 @@ config THERMAL_EMULATION
because userland can easily disable the thermal policy by simply
flooding this sysfs node with low temperature values.

+config IIO_THERMAL
+ tristate "Temperature sensor driver for generic IIO channels"
+ depends on IIO
+ depends on THERMAL_OF
+ help
+ Support for generic IIO channels, such as ADCs. This driver allows
+ you to expose an IIO voltage channel as a thermal sensor. This is
+ implemented as a thermal sensor, not a thermal zone, and thus
+ requires DT defined thermal infrastructure in order to be useful.
+
+ If you aren't sure that you need this support, or haven't configured
+ a thermal infrastructure in device tree, you should say 'N' here.
+
config IMX_THERMAL
tristate "Temperature sensor driver for Freescale i.MX SoCs"
depends on CPU_THERMAL
diff --git a/drivers/thermal/Makefile b/drivers/thermal/Makefile
index 54e4ec9..0ee2c92 100644
--- a/drivers/thermal/Makefile
+++ b/drivers/thermal/Makefile
@@ -25,6 +25,7 @@ obj-y += samsung/
obj-$(CONFIG_DOVE_THERMAL) += dove_thermal.o
obj-$(CONFIG_DB8500_THERMAL) += db8500_thermal.o
obj-$(CONFIG_ARMADA_THERMAL) += armada_thermal.o
+obj-$(CONFIG_IIO_THERMAL) += iio_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
diff --git a/drivers/thermal/iio_thermal.c b/drivers/thermal/iio_thermal.c
new file mode 100644
index 0000000..df21dbc
--- /dev/null
+++ b/drivers/thermal/iio_thermal.c
@@ -0,0 +1,207 @@
+/*
+ * An IIO channel based thermal sensor driver
+ *
+ * Copyright (C) 2014 Sony Mobile Communications, AB
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; version 2 of the License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * General Public License for more details.
+ */
+
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/iio/iio.h>
+#include <linux/iio/consumer.h>
+#include <linux/thermal.h>
+#include <linux/err.h>
+#include <linux/of.h>
+
+#define MILLIKELVIN_0C 273150
+
+struct iio_thermal_conv {
+ s32 *values;
+ int ntuple;
+ long (*convert)(const struct iio_thermal_conv *, int val);
+};
+
+struct iio_thermal {
+ struct thermal_zone_device *tz;
+ struct iio_channel *chan;
+ struct iio_thermal_conv conv;
+};
+
+static int iio_bsearch(const struct iio_thermal_conv *conv, s32 input)
+{
+ int h = conv->ntuple - 1;
+ int l = 0;
+
+ while (h - 1 > l) {
+ int m = (l + h) & ~1;
+ s32 v = conv->values[m];
+ if (v < input)
+ l = m >> 1;
+ else
+ h = m >> 1;
+ }
+
+ return h;
+}
+
+static long iio_thermal_interpolate(const struct iio_thermal_conv *conv, int v)
+{
+ int n;
+
+ n = iio_bsearch(conv, v);
+ if (n == 0 || n == conv->ntuple) {
+ BUG();
+ } else {
+ s32 *pts = &conv->values[(n-1)*2];
+ s32 sx = pts[3] - pts[1];
+ s32 sy = pts[2] - pts[0];
+ return sx * (v - pts[0]) / sy + pts[1];
+ }
+}
+
+static long iio_thermal_scale(const struct iio_thermal_conv *conv, int v)
+{
+ return div_s64((s64)v * conv->values[0], conv->values[1]);
+}
+
+static int iio_thermal_get_temp(void *pdata, long *value)
+{
+ struct iio_thermal *iio = pdata;
+ long temp;
+ int val;
+ int rc;
+
+ rc = iio_read_channel_processed(iio->chan, &val);
+ if (rc)
+ return rc;
+
+ temp = iio->conv.convert(&iio->conv, val);
+
+ /* thermal core wants milli-celsius; we deal in milli-kelvin */
+ temp = temp - MILLIKELVIN_0C;
+
+ /*
+ * Although it would appear that the temperature value here is a
+ * signed value for sensors, the underlying thermal zone core
+ * doesn't deal with negative temperature. Cut this value off at 0C.
+ */
+ *value = (temp < 0) ? 0 : temp;
+
+ return 0;
+}
+
+static int iio_thermal_probe(struct platform_device *pdev)
+{
+ struct iio_thermal *iio;
+ const void *values;
+ const char *type;
+ int rc;
+
+ dev_info(&pdev->dev, "registering IIO thermal device\n");
+ iio = devm_kzalloc(&pdev->dev, sizeof(*iio), GFP_KERNEL);
+ if (!iio)
+ return -ENOMEM;
+
+ values = of_get_property(pdev->dev.of_node,
+ "conversion-values", &iio->conv.ntuple);
+ if (values == NULL || (iio->conv.ntuple % (sizeof(u32) * 2)) != 0) {
+ dev_err(&pdev->dev, "invalid/missing conversion values\n");
+ return -EINVAL;
+ }
+ iio->conv.ntuple /= sizeof(u32) * 2;
+ iio->conv.values = devm_kzalloc(&pdev->dev,
+ sizeof(u32) * 2 * iio->conv.ntuple, GFP_KERNEL);
+ if (!iio->conv.values)
+ return -ENOMEM;
+
+ rc = of_property_read_u32_array(pdev->dev.of_node,
+ "conversion-values", (u32 *)iio->conv.values,
+ iio->conv.ntuple * 2);
+ if (rc) {
+ dev_err(&pdev->dev, "invalid/missing conversion values\n");
+ return -EINVAL;
+ }
+
+ rc = of_property_read_string(pdev->dev.of_node,
+ "conversion-method", &type);
+ if (rc) {
+ dev_err(&pdev->dev, "invalid/missing conversion method\n");
+ return rc;
+ }
+ if (!strcmp(type, "interpolation") && iio->conv.ntuple > 1) {
+ if (iio->conv.values[0] > iio->conv.values[2]) {
+ dev_err(&pdev->dev,
+ "conversion values should ascend\n");
+ return rc;
+ }
+ iio->conv.convert = iio_thermal_interpolate;
+ } else if (!strcmp(type, "scalar") && iio->conv.ntuple == 1) {
+ iio->conv.convert = iio_thermal_scale;
+ } else {
+ dev_err(&pdev->dev, "invalid conversion method for values\n");
+ return rc;
+ }
+
+ iio->chan = iio_channel_get(&pdev->dev, NULL);
+ if (IS_ERR(iio->chan)) {
+ dev_err(&pdev->dev, "invalid/missing iio channel\n");
+ return PTR_ERR(iio->chan);
+ }
+ if (iio->chan->channel->type != IIO_VOLTAGE) {
+ dev_err(&pdev->dev, "specified iio channel is not voltage\n");
+ iio_channel_release(iio->chan);
+ return -EINVAL;
+ }
+ platform_set_drvdata(pdev, iio);
+
+ iio->tz = thermal_zone_of_sensor_register(&pdev->dev, 0, iio,
+ iio_thermal_get_temp, NULL);
+ if (IS_ERR(iio->tz)) {
+ dev_err(&pdev->dev, "failed to register thermal sensor\n");
+ iio_channel_release(iio->chan);
+ return PTR_ERR(iio->tz);
+ }
+ dev_info(&pdev->dev, "successfully registered IIO thermal sensor\n");
+
+ return 0;
+}
+
+static int iio_thermal_remove(struct platform_device *pdev)
+{
+ struct iio_thermal *iio;
+
+ iio = platform_get_drvdata(pdev);
+
+ thermal_zone_of_sensor_unregister(&pdev->dev, iio->tz);
+ iio_channel_release(iio->chan);
+
+ return 0;
+}
+
+static const struct of_device_id iio_thermal_match[] = {
+ { .compatible = "iio-thermal", },
+ { }
+};
+MODULE_DEVICE_TABLE(of, iio_thermal_match);
+
+static struct platform_driver iio_thermal = {
+ .driver = {
+ .name = "iio-thermal",
+ .owner = THIS_MODULE,
+ .of_match_table = iio_thermal_match,
+ },
+ .probe = iio_thermal_probe,
+ .remove = iio_thermal_remove,
+};
+module_platform_driver(iio_thermal);
+
+MODULE_DESCRIPTION("Thermal driver for IIO ADCs");
+MODULE_LICENSE("GPL v2");
--
1.8.1.5


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