Re: [PATCH v2 1/9] Input: sun4i-ts: Add thermal zone sensor support

On Sat, Jan 10, 2015 at 2:28 AM, Chen-Yu Tsai [off-list ref] wrote:

On Sat, Jan 10, 2015 at 1:23 AM, Dmitry Torokhov
[off-list ref] wrote:

quoted

On Fri, Jan 09, 2015 at 06:17:48PM +0800, Chen-Yu Tsai wrote:

quoted

The touchscreen controller has a temperature sensor embedded in the SoC,
which already has hwmon support in the driver.

Add DT thermal zone support so we can use it with cpufreq for thermal
throttling.

This also adds a comment stating that we do not know the actual formula
for calculating the temperature.

Signed-off-by: Chen-Yu Tsai <redacted>
---

  CC [M]  drivers/input/touchscreen/sun4i-ts.o
drivers/input/touchscreen/sun4i-ts.c:208:15: error: variable
‘sun4i_ts_tz_ops’ has initializer but incomplete type
 static struct thermal_zone_of_device_ops sun4i_ts_tz_ops = {
               ^
drivers/input/touchscreen/sun4i-ts.c:209:2: error: unknown field
‘get_temp’ specified in initializer
  .get_temp = get_temp,
  ^
drivers/input/touchscreen/sun4i-ts.c:209:2: warning: excess elements in
struct initializer [enabled by default]
drivers/input/touchscreen/sun4i-ts.c:209:2: warning: (near
initialization for ‘sun4i_ts_tz_ops’) [enabled by default]
drivers/input/touchscreen/sun4i-ts.c: In function ‘sun4i_ts_probe’:
drivers/input/touchscreen/sun4i-ts.c:331:8: warning: passing argument 4
of ‘thermal_zone_of_sensor_register’ from incompatible pointer type
[enabled by default]
        &sun4i_ts_tz_ops);
        ^
In file included from drivers/input/touchscreen/sun4i-ts.c:37:0:
include/linux/thermal.h:302:1: note: expected ‘int (*)(void *, long int
*)’ but argument is of type ‘struct thermal_zone_of_device_ops *’
 thermal_zone_of_sensor_register(struct device *dev, int id,
 ^
drivers/input/touchscreen/sun4i-ts.c:331:8: error: too few arguments to
function ‘thermal_zone_of_sensor_register’
        &sun4i_ts_tz_ops);
        ^
In file included from drivers/input/touchscreen/sun4i-ts.c:37:0:
include/linux/thermal.h:302:1: note: declared here
 thermal_zone_of_sensor_register(struct device *dev, int id,
 ^
make[1]: *** [drivers/input/touchscreen/sun4i-ts.o] Error 1
make: *** [drivers/input/touchscreen/sun4i-ts.o] Error 2

struct thermal_zone_of_device_ops was introduced in 3.19-rc1 in

    184a4bf623fa thermal: of: Extend current of-thermal.c code to
allow setting emulated temp

quoted

quoted

changes since v1:

    - clean up thermal zone sensor when input device register fails
    - unconditionally unregister thermal zone sensor on removal.
      the unregister function checks the pointers passed in.
    - add comment explaining the lack of documents for the temperature
      calculation formula

---
 .../bindings/input/touchscreen/sun4i.txt           |  2 +
 drivers/input/touchscreen/sun4i-ts.c               | 47 ++++++++++++++++++++++
 2 files changed, 49 insertions(+)

diff --git a/Documentation/devicetree/bindings/input/touchscreen/sun4i.txt b/Documentation/devicetree/bindings/input/touchscreen/sun4i.txt
index aef57791f40b..a8405bab6c00 100644
--- a/Documentation/devicetree/bindings/input/touchscreen/sun4i.txt
+++ b/Documentation/devicetree/bindings/input/touchscreen/sun4i.txt

@@ -5,6 +5,7 @@ Required properties:
  - compatible: "allwinner,sun4i-a10-ts"
  - reg: mmio address range of the chip
  - interrupts: interrupt to which the chip is connected
+ - #thermal-sensor-cells: shall be 0

 Optional properties:
  - allwinner,ts-attached: boolean indicating that an actual touchscreen is

@@ -17,4 +18,5 @@ Example:
              reg = <0x01c25000 0x100>;
              interrupts = <29>;
              allwinner,ts-attached;
+             #thermal-sensor-cells = <0>;
      };

diff --git a/drivers/input/touchscreen/sun4i-ts.c b/drivers/input/touchscreen/sun4i-ts.c
index 28a06749ae42..aac49db0b09d 100644
--- a/drivers/input/touchscreen/sun4i-ts.c
+++ b/drivers/input/touchscreen/sun4i-ts.c

@@ -34,6 +34,7 @@

 #include <linux/err.h>
 #include <linux/hwmon.h>
+#include <linux/thermal.h>
 #include <linux/init.h>
 #include <linux/input.h>
 #include <linux/interrupt.h>

@@ -107,6 +108,7 @@
 struct sun4i_ts_data {
      struct device *dev;
      struct input_dev *input;
+     struct thermal_zone_device *tz;
      void __iomem *base;
      unsigned int irq;
      bool ignore_fifo_data;

@@ -180,6 +182,33 @@ static void sun4i_ts_close(struct input_dev *dev)
      writel(TEMP_IRQ_EN(1), ts->base + TP_INT_FIFOC);
 }

+static int get_temp(void *data, long *temp)
+{
+     struct sun4i_ts_data *ts = data;
+
+     /* No temp_data until the first irq */
+     if (ts->temp_data == -1)
+             return -EAGAIN;
+
+     /*
+      * The user manuals do not contain the formula for calculating
+      * the temperature. The formula used here is from the AXP209,
+      * which is designed by X-Powers, an affiliate of Allwinner:
+      *
+      *     temperature = -144.7 + (value * 0.1)
+      *
+      * This should be replaced with the correct one if such information
+      * becomes available.
+      */
+     *temp = (ts->temp_data - 1447) * 100;
+
+     return 0;
+}
+
+static struct thermal_zone_of_device_ops sun4i_ts_tz_ops = {
+     .get_temp = get_temp,
+};
+
 static ssize_t show_temp(struct device *dev, struct device_attribute *devattr,
                       char *buf)
 {

@@ -189,6 +218,16 @@ static ssize_t show_temp(struct device *dev, struct device_attribute *devattr,
      if (ts->temp_data == -1)
              return -EAGAIN;

+     /*
+      * The user manuals do not contain the formula for calculating
+      * the temperature. The formula used here is from the AXP209,
+      * which is designed by X-Powers, an affiliate of Allwinner:
+      *
+      *     temperature = -144.7 + (value * 0.1)
+      *
+      * This should be replaced with the correct one if such information
+      * becomes available.
+      */
      return sprintf(buf, "%d\n", (ts->temp_data - 1447) * 100);

Why duplicate it here, instead of doing:

static int sun4i_get_temp(struct sun4i_ts_data *ts, int *temp)
{
        if (ts->temp_data == -1)
                return -EAGAIN;

        /* comment */
        *temp = (ts->temp_data - 1447) * 100);

        return 0;
}

static int sun4i_tz_get_temp(void *data, long *temp)
{
        return sun4i_get_temp(data, temp);
}

static ssize_t sun4i_show_temp(...)
{
        error = sun4i_get_temp(ts, &temp);
        if (error)
                return error;

        return sprintf(buf, "%d\n", temp);
}

I suppose that would be better, especially after I added the large comment.

quoted

Also, thermal core seems to allow creating hwmon devices for thermal
zones, can we use this feature?

For thermal sensors that also have hwmon devices registered, that step is
skipped.

I sort of like having separate hwmon bits, just for a nicer, more informative
label. But I am not opposed to removing the bits from the driver and having
it go through the thermal core. We could also remove the build dependency
on HWMON as a result.

OK. Just took a look at the thermal core. For DT based thermal zones, it
does not create hwmon devices at all, possible to avoid duplicate devices
which it cannot know about.

I'll clean up the duplicate code and send v3.


ChenYu