Input: sun4i-ts - add support for touchpanel controller on A31

The Allwinner A31 SoC (sun6i) has the same resistive touchpanel controller
as on other sunxi platforms. The only difference between the variants is
the control bits for enabling operations are left-shifted by 1 on the A31.

Also update the comment for the original temperature sensor with
information from Allwinner.
Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

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

@@ -2,7 +2,7 @@ sun4i resistive touchscreen controller
 --------------------------------------
 
 Required properties:
- - compatible: "allwinner,sun4i-a10-ts"
+ - compatible: "allwinner,sun4i-a10-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

@@ -72,6 +72,9 @@
 #define TP_ADC_SELECT(x)	((x) << 3)
 #define ADC_CHAN_SELECT(x)	((x) << 0)  /* 3 bits */
 
+/* on sun6i, bits 3~6 are left shifted by 1 to 4~7 */
+#define SUN6I_TP_MODE_EN(x)	((x) << 5)
+
 /* TP_CTRL2 bits */
 #define TP_SENSITIVE_ADJUST(x)	((x) << 28) /* 4 bits */
 #define TP_MODE_SELECT(x)	((x) << 26) /* 2 bits */
@@ -113,6 +116,8 @@ struct sun4i_ts_data {
 	unsigned int irq;
 	bool ignore_fifo_data;
 	int temp_data;
+	int temp_offset;
+	int temp_step;
 };
 
 static void sun4i_ts_irq_handle_input(struct sun4i_ts_data *ts, u32 reg_val)
@@ -188,17 +193,7 @@ static int sun4i_get_temp(const struct sun4i_ts_data *ts, long *temp)
 	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;
+	*temp = (ts->temp_data - ts->temp_offset) * ts->temp_step;
 
 	return 0;
 }
@@ -249,6 +244,7 @@ static int sun4i_ts_probe(struct platform_device *pdev)
 	struct device_node *np = dev->of_node;
 	struct device *hwmon;
 	int error;
+	u32 reg;
 	bool ts_attached;
 
 	ts = devm_kzalloc(dev, sizeof(struct sun4i_ts_data), GFP_KERNEL);
@@ -258,6 +254,25 @@ static int sun4i_ts_probe(struct platform_device *pdev)
 	ts->dev = dev;
 	ts->ignore_fifo_data = true;
 	ts->temp_data = -1;
+	if (of_device_is_compatible(np, "allwinner,sun6i-a31-ts")) {
+		/* Allwinner SDK has temperature = -271 + (value / 6) (C) */
+		ts->temp_offset = 1626;
+		ts->temp_step = 167;
+	} else {
+		/*
+		 * 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)
+		 *
+		 * Allwinner does not have any documentation whatsoever for
+		 * this hardware. Moreover, it is claimed that the sensor
+		 * is inaccurate and cannot work properly.
+		 */
+		ts->temp_offset = 1447;
+		ts->temp_step = 100;
+	}
 
 	ts_attached = of_property_read_bool(np, "allwinner,ts-attached");
 	if (ts_attached) {
@@ -314,8 +329,12 @@ static int sun4i_ts_probe(struct platform_device *pdev)
 	 * Set stylus up debounce to aprox 10 ms, enable debounce, and
 	 * finally enable tp mode.
 	 */
-	writel(STYLUS_UP_DEBOUN(5) | STYLUS_UP_DEBOUN_EN(1) | TP_MODE_EN(1),
-	       ts->base + TP_CTRL1);
+	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
+		reg |= SUN6I_TP_MODE_EN(1);
+	writel(reg, ts->base + TP_CTRL1);
 
 	/*
 	 * The thermal core does not register hwmon devices for DT-based
@@ -364,6 +383,7 @@ 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,sun6i-a31-ts", },
 	{ /* sentinel */ }
 };
 MODULE_DEVICE_TABLE(of, sun4i_ts_of_match);