[PATCH v9 4/8] drivers:input:ads7846(+tsc2046): add new common binding names, pre-calibration and flipping

H. Nikolaus Schaller
2016-12-28T14:53:47Z

commit b98abe52fa8e ("Input: add common DT binding for touchscreens")
introduced common DT bindings for touchscreens [1] and a helper function to
parse the DT.

commit ed7c9870c9bc ("Input: of_touchscreen - add support for inverted / swapped axes")
added another helper for parsing axis inversion and swapping
and applying them to x and y coordinates.

Both helpers have been integrated to accommodate any orientation of the
touch panel in relation to the LCD.

A new feature is to introduce scaling the min/max ADC values to the screen
size.

This makes it possible to pre-calibrate the touch so that is (almost)
exactly matches the LCD pixel coordinates it is glued onto. This allows to
well enough operate the touch before a user space calibration step can
improve the precision.

[1]: Documentation/devicetree/bindings/input/touchscreen/touchscreen.txt

Signed-off-by: H. Nikolaus Schaller <hns@goldelico.com>
Acked-by: Rob Herring <robh@kernel.org>
---
.../devicetree/bindings/input/ads7846.txt | 9 +++-
drivers/input/touchscreen/ads7846.c | 60 ++++++++++++++++++----
2 files changed, 57 insertions(+), 12 deletions(-)

diff --git a/Documentation/devicetree/bindings/input/ads7846.txt b/Documentation/devicetree/bindings/input/ads7846.txt
index 9fc47b0..29f91ed 100644
--- a/Documentation/devicetree/bindings/input/ads7846.txt
+++ b/Documentation/devicetree/bindings/input/ads7846.txt
@@ -26,6 +26,12 @@ 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).
@@ -33,7 +39,7 @@ Optional properties:
(ADS7846).
ti,keep-vref-on set to keep vref on for differential
measurements as well
- ti,swap-xy swap x and y axis
+ ti,swap-xy deprecated name for touchscreen-swapped-x-y
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,
@@ -82,6 +88,7 @@ Example for a TSC2046 chip connected to an McSPI controller of an OMAP SoC::
pendown-gpio = <&gpio1 8 0>;
vcc-supply = <&reg_vcc3>;

+ touchscreen-swapped-x-y;
ti,x-min = /bits/ 16 <0>;
ti,x-max = /bits/ 16 <8000>;
ti,y-min = /bits/ 16 <0>;
diff --git a/drivers/input/touchscreen/ads7846.c b/drivers/input/touchscreen/ads7846.c
index 1ce3ecb..400e421 100644
--- a/drivers/input/touchscreen/ads7846.c
+++ b/drivers/input/touchscreen/ads7846.c
@@ -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 +110,13 @@ 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;
+
+ struct touchscreen_properties prop;

- bool swap_xy;
bool use_internal;

struct ads7846_packet *packet;
@@ -825,22 +831,36 @@ static void ads7846_report_state(struct ads7846 *ts)
*/
if (Rt) {
struct input_dev *input = ts->input;
+ int sx, sy;
+
+ dev_dbg(&ts->spi->dev,
+ "Raw point(%4d,%4d), pressure (%4u)\n",
+ x, y, Rt);
+
+ /* scale ADC values to desired output range */
+ sx = (ts->prop.max_x * (x - ts->x_min))
+ / (ts->x_max - ts->x_min);
+ sy = (ts->prop.max_y * (y - ts->y_min))
+ / (ts->y_max - ts->y_min);

- if (ts->swap_xy)
- swap(x, y);
+ dev_dbg(&ts->spi->dev,
+ "Scaled point(%4d,%4d), pressure (%4u)\n",
+ sx, sy, Rt);

+ /* report event */
if (!ts->pendown) {
input_report_key(input, BTN_TOUCH, 1);
ts->pendown = true;
dev_vdbg(&ts->spi->dev, "DOWN\n");
}

- input_report_abs(input, ABS_X, x);
- input_report_abs(input, ABS_Y, y);
+ touchscreen_report_pos(ts->input, &ts->prop,
+ (unsigned int) sx, (unsigned int) sy,
+ false);
input_report_abs(input, ABS_PRESSURE, ts->pressure_max - Rt);

input_sync(input);
- dev_vdbg(&ts->spi->dev, "%4d/%4d/%4d\n", x, y, Rt);
+ dev_vdbg(&ts->spi->dev, "%4d/%4d/%4d\n", sx, sy, Rt);
}
}

@@ -1212,6 +1232,8 @@ static const struct ads7846_platform_data *ads7846_probe_dt(struct device *dev)
pdata->keep_vref_on = of_property_read_bool(node, "ti,keep-vref-on");

pdata->swap_xy = of_property_read_bool(node, "ti,swap-xy");
+ if (pdata->swap_xy)
+ dev_notice(dev, "please update device tree to use touchscreen-swapped-x-y");

of_property_read_u16(node, "ti,settle-delay-usec",
&pdata->settle_delay_usecs);
@@ -1315,7 +1337,6 @@ static int ads7846_probe(struct spi_device *spi)
ts->pressure_max = pdata->pressure_max ? : ~0;

ts->vref_mv = pdata->vref_mv;
- ts->swap_xy = pdata->swap_xy;

if (pdata->filter != NULL) {
if (pdata->filter_init != NULL) {
@@ -1355,18 +1376,35 @@ static int ads7846_probe(struct spi_device *spi)
input_dev->dev.parent = &spi->dev;

input_dev->evbit[0] = BIT_MASK(EV_KEY) | BIT_MASK(EV_ABS);
+ input_dev->absbit[0] = BIT_MASK(ABS_X) | BIT_MASK(ABS_Y) |
+ BIT_MASK(ABS_PRESSURE);
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_abs_set_min(input_dev, ABS_X, 0);
+ input_abs_set_min(input_dev, ABS_Y, 0);
+
+ touchscreen_parse_properties(ts->input, false, &ts->prop);
+ }
+
+ ts->prop.swap_x_y |= pdata->swap_xy;
+
ads7846_setup_spi_msg(ts, pdata);

ts->reg = regulator_get(&spi->dev, "vcc");
--
2.7.3