Input: sun4i-ts - A10 (sun4i) has a different temperature curve

Testing has revealed that the temperature in the rtp controller of the A10
(sun4i) SoC has a different curve then on the A13 (sun5i) and later models.

Add a new sun5i-a13-ts compatible to differentiate the newer models and
set the curve based on the compatible string.

The new curve is still not ideal on all A10-s, that seems to have to
do with there being a large spread between different A10-s out there,
the new curve us based on callibration results on 4 completely different
models:
                        raw min raw max temp min temp max stepsize offset
Tong Zhang's hackberry    2402    2680    45.0     80.0    0.125   -255.3
Hansg's Cubieboard        2207    2300    36.0     45.0    0.096   -175.8
Olliver's lime 1 (*):     2258    2537    48.3     87.1    0.139   -265.7
Olliver's lime 2 (*):     2222    2486    46.7     91.7    0.170   -331.0
*) from: http://linux-sunxi.org/Temperature_Calibration

Average all 4:                                             0.133   -257.0
Average without outliers (middle 2):                       0.132   -261.0

Since it is better to slightly overreport the temperature this patch uses
the average of all 4 as curve.

This fixes the temperature reported on the A10 being much higher then
expected.

Reported-by: Tong Zhang <lovewilliam@gmail.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

Documentation/devicetree/bindings/input/touchscreen/sun4i.txt

@@ -2,7 +2,8 @@ sun4i resistive touchscreen controller
 --------------------------------------
 
 Required properties:
- - compatible: "allwinner,sun4i-a10-ts" or "allwinner,sun6i-a31-ts"
+ - compatible: "allwinner,sun4i-a10-ts", "allwinner,sun5i-a13-ts" or
+   "allwinner,sun6i-a31-ts"
  - reg: mmio address range of the chip
  - interrupts: interrupt to which the chip is connected
  - #thermal-sensor-cells: shall be 0

drivers/input/touchscreen/sun4i-ts.c

@@ -258,6 +258,15 @@ static int sun4i_ts_probe(struct platform_device *pdev)
 		/* Allwinner SDK has temperature = -271 + (value / 6) (C) */
 		ts->temp_offset = 1626;
 		ts->temp_step = 167;
+	} else if (of_device_is_compatible(np, "allwinner,sun4i-a10-ts")) {
+		/*
+		 * The A10 temperature sensor has quite a wide spread, these
+		 * parameters are based on the averaging of the calibration
+		 * results of 4 completely different boards, with a spread of
+		 * temp_step from 96 - 170 and temp_offset from 1758 - 3310.
+		 */
+		ts->temp_offset = 2570;
+		ts->temp_step = 133;
 	} else {
 		/*
 		 * The user manuals do not contain the formula for calculating
@@ -330,10 +339,10 @@ static int sun4i_ts_probe(struct platform_device *pdev)
 	 * finally enable tp mode.
 	 */
 	reg = STYLUS_UP_DEBOUN(5) | STYLUS_UP_DEBOUN_EN(1);
-	if (of_device_is_compatible(np, "allwinner,sun4i-a10-ts"))
-		reg |= TP_MODE_EN(1);
-	else
+	if (of_device_is_compatible(np, "allwinner,sun6i-a31-ts"))
 		reg |= SUN6I_TP_MODE_EN(1);
+	else
+		reg |= TP_MODE_EN(1);
 	writel(reg, ts->base + TP_CTRL1);
 
 	/*
@@ -383,6 +392,7 @@ static int sun4i_ts_remove(struct platform_device *pdev)
 
 static const struct of_device_id sun4i_ts_of_match[] = {
 	{ .compatible = "allwinner,sun4i-a10-ts", },
+	{ .compatible = "allwinner,sun5i-a13-ts", },
 	{ .compatible = "allwinner,sun6i-a31-ts", },
 	{ /* sentinel */ }
 };