@@ -26,12 +26,17 @@ Additional required properties:
Optional properties:
+You can optionally specify any of the touchscreen parameters described in
+
+ Documentation/devicetree/bindings/input/touchscreen/touchscreen.txt
+
+This allows to scale, invert or swap coordinates and define the fuzz factors.
+
ti,vref-delay-usecs vref supply delay in usecs, 0 for
external vref (u16).
ti,vref-mv The VREF voltage, in millivolts (u16).
ti,keep-vref-on set to keep vref on for differential
measurements as well
- ti,swap-xy swap x and y axis
ti,settle-delay-usec Settling time of the analog signals;
a function of Vcc and the capacitance
on the X/Y drivers. If set to non-zero,
@@ -79,6 +84,7 @@ Example for a TSC2046 chip connected to an McSPI controller of an OMAP SoC::
pendown-gpio = <&gpio1 8 0>;
vcc-supply = <®_vcc3>;
+ touchscreen-swapped-x-y;
ti,x-min = /bits/ 16 <0>;
ti,x-max = /bits/ 16 <8000>;
ti,y-min = /bits/ 16 <0>;
@@ -34,6 +34,7 @@
#include <linux/spi/ads7846.h>
#include <linux/regulator/consumer.h>
#include <linux/module.h>
+#include <linux/input/touchscreen.h>
#include <asm/irq.h>
/*
@@ -109,8 +110,14 @@ struct ads7846 {
u16 vref_delay_usecs;
u16 x_plate_ohms;
u16 pressure_max;
+ u16 x_min;
+ u16 x_max;
+ u16 y_min;
+ u16 y_max;
bool swap_xy;
+ bool invert_x;
+ bool invert_y;
bool use_internal;
struct ads7846_packet *packet;
@@ -828,9 +835,48 @@ static void ads7846_report_state(struct ads7846 *ts)
if (Rt) {
struct input_dev *input = ts->input;
+ dev_dbg(&ts->spi->dev,
+ "Raw point(%4d,%4d), pressure (%4u)\n",
+ x, y, Rt);
+ /* clamp to expected ADC range */
+ if (x < ts->x_min)
+ x = ts->x_min;
+ if (x > ts->x_max)
+ x = ts->x_max;
+ if (y < ts->y_min)
+ y = ts->y_min;
+ if (y > ts->y_max)
+ y = ts->y_max;
+
+ dev_dbg(&ts->spi->dev,
+ "Clamped point(%4d,%4d), pressure (%4u)\n",
+ x, y, Rt);
+
+ /* flip */
+ if (ts->invert_x)
+ x = (ts->x_max - x) + ts->x_min;
+ if (ts->invert_y)
+ y = (ts->y_max - y) + ts->y_min;
+
+ dev_dbg(&ts->spi->dev,
+ "Flipped point(%4d,%4d), pressure (%4u)\n",
+ x, y, Rt);
+
+ /* scale to desired output range */
+ x = (input->absinfo[ABS_X].maximum * (x - ts->x_min))
+ / (ts->x_max - ts->x_min);
+ y = (input->absinfo[ABS_Y].maximum * (y - ts->y_min))
+ / (ts->y_max - ts->y_min);
+
+ dev_dbg(&ts->spi->dev,
+ "Scaled point(%4d,%4d), pressure (%4u)\n",
+ x, y, Rt);
+
+ /* swap x and y */
if (ts->swap_xy)
swap(x, y);
+ /* report event */
if (!ts->pendown) {
input_report_key(input, BTN_TOUCH, 1);
ts->pendown = true;
@@ -1213,7 +1259,7 @@ static const struct ads7846_platform_data *ads7846_probe_dt(struct device *dev)
of_property_read_u16(node, "ti,vref-mv", &pdata->vref_mv);
pdata->keep_vref_on = of_property_read_bool(node, "ti,keep-vref-on");
- pdata->swap_xy = of_property_read_bool(node, "ti,swap-xy");
+ pdata->swap_xy = of_property_read_bool(node, "touchscreen-swapped-x-y");
of_property_read_u16(node, "ti,settle-delay-usec",
&pdata->settle_delay_usecs);
@@ -1358,17 +1404,33 @@ static int ads7846_probe(struct spi_device *spi)
input_dev->evbit[0] = BIT_MASK(EV_KEY) | BIT_MASK(EV_ABS);
input_dev->keybit[BIT_WORD(BTN_TOUCH)] = BIT_MASK(BTN_TOUCH);
+
+ ts->x_min = pdata->x_min ? : 0;
+ ts->x_max = pdata->x_max ? : MAX_12BIT;
+ ts->y_min = pdata->y_min ? : 0;
+ ts->y_max = pdata->y_max ? : MAX_12BIT;
+
input_set_abs_params(input_dev, ABS_X,
- pdata->x_min ? : 0,
- pdata->x_max ? : MAX_12BIT,
+ ts->x_min,
+ ts->x_max,
0, 0);
input_set_abs_params(input_dev, ABS_Y,
- pdata->y_min ? : 0,
- pdata->y_max ? : MAX_12BIT,
+ ts->y_min,
+ ts->y_max,
0, 0);
input_set_abs_params(input_dev, ABS_PRESSURE,
pdata->pressure_min, pdata->pressure_max, 0, 0);
+ if (spi->dev.of_node) {
+ input_dev->absinfo[ABS_X].minimum = 0;
+ input_dev->absinfo[ABS_Y].minimum = 0;
+ ts->invert_x = of_property_read_bool(spi->dev.of_node,
+ "touchscreen-inverted-x");
+ ts->invert_y = of_property_read_bool(spi->dev.of_node,
+ "touchscreen-inverted-y");
+ touchscreen_parse_properties(input_dev, false);
+ }
+
ads7846_setup_spi_msg(ts, pdata);
ts->reg = regulator_get(&spi->dev, "vcc");
commit b98abe52fa8e ("Input: add common DT binding for touchscreens") introduced common DT bindings for touchscreens [1] and a helper function to parse the DT. This has been integrated and interpretation of the inversion (flipping) properties for the x and y axis has been added to accommodate any orientation of the touch in relation to the LCD. By scaling the min/max ADC values to the screen size it is now possible to pre-calibrate the touch so that is (almost) exactly matches the LCD it is glued onto. This allows to well enough operate the touch before a user space calibration can improve the precision. [1]: Documentation/devicetree/bindings/input/touchscreen/touchscreen.txt Signed-off-by: H. Nikolaus Schaller <hns@goldelico.com> --- .../devicetree/bindings/input/ads7846.txt | 8 ++- drivers/input/touchscreen/ads7846.c | 72 ++++++++++++++++++++-- 2 files changed, 74 insertions(+), 6 deletions(-)